We synthesized biodegradable and economically viable solid-state electrolyte films based on konjac glucomannan (KG) and sodium iodide (NaI). Among the KGNaI-x (x = 31-69 wt%) films, KGNaI-69 exhibits superior flexibility, biodegradability, and sodium superionic conductivity of 77.9 mS cm-1. The KGNaI-69-based supercapacitor delivers outstanding electrochemical efficiency and cycling stability, retaining 84.4% capacitance after 5000 cycles establishing its potentiality toward flexible energy storage devices.

Inducing post-transition metals in an oxide semiconductor system has a high potential for use in storage for neuromorphic computing. It is challenging to find a material that can be switched stably between multiple resistance states. This research explores the memristive properties of Sn (post-transition metal)-doped ZnO (SZO) thin films, emphasizing their application in memristor devices. The (magnetron sputtered) synthesized SZO thin films in the form of Ag/SZO/Au/Ti/SiO₂ device demonstrated a clear bipolar resistive switching (BRS) behavior with VSET and VRESET of 1.0 V and −0.75 V, respectively. The memristor could change between a high resistance state and a low resistance state with a high RON/OFF rate of 104, mimicking synaptic behaviors such as potentiation and depression. This switching is attributed to the formation and dissolution of Ag filaments within the SZO layer, influenced by the migration of Ag⁺ ions and the presence of oxygen vacancies. These vacancies facilitate the formation of conductive filaments under positive bias and their dissolution under negative bias. The endurance and retention tests showed stable switching characteristics, with the memristor maintaining distinct HRS and LRS over 100 cycles and retaining these states for over 5K seconds without significant degradation. Finally, the nonlinearity values for potentiation and depression were αp∼1.6 and αd ∼ -0.14, suggesting that the memristor may be more responsive to increasing synaptic weights in biological systems. The linearity response at a very small pulse width showed the device is more applicable for neuromorphic applications. The observed memristor combined with stable endurance and retention performance, suggests that this memristor structure could play a crucial role in the development of artificial synapses and memory technologies.

Herein, we synthesized a Cu2O and Co3O4 incorporation with MoS2 to produce MoS2/Co3O4/Cu2O nanocomposites by facile sonication assisted hydrothermal methods. The phase structure and elemental composition of MoS2/Co3O4/Cu2O nanocomposites were investigated using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) morphology studies confirm that MoS2/Co3O4 nanostructure self-assembles in a mixed nanosheet configuration after the introduction of Cu2O. The synthesized samples were used as new types of Pt-free counter electrodes (CE) for DSSCs. Among all, the DSSCs based on the MoS2/Co3O4/Cu2O CE yields a maximum power conversion efficiency of 3.68 % (Jsc = 8.2 mA cm−2, Voc = 0.71 mV and FF = 0.629 %) under the standard AM 1.5 G illumination, which is 2.5 times higher than that of pure MoS2. To assess the photocatalytic activity, prepared samples were used to suppress methylene blue (MB) and rhodamine B (RhB) dye under UV–visible light irradiation. The MoS2/Co3O4/Cu2O nanocomposites had the highest photocatalytic degradation efficiency of all the samples. It increased degradation efficiency from 43 % to 91 % for MB dye after 100 minutes, and from 47 % to 92 % for RhB dye after 90 minutes. Scavengers test analysis proved that the superoxide radical (•O2−) play a major role in the MoS2/Co3O4/Cu2O photocatalytic system. After four consecutive photocatalytic cycles, the crystal structure and surface morphology of the MoS2/Co3O4/Cu2O nanocomposites used in the 4th cycle were more stable, and this was confirmed by SEM, EDAX and XRD studies. The broader significance of these findings provides a straightforward approach for synthesizing a low-cost and high-efficiency MoS2/Co3O4/Cu2O nanocomposite for CE in DSSC photovoltaic cells and facilitates organic pollutant removal through photocatalytic applications.

Li-containing ternary vanadates are known for their remarkable structural diversity and tunable physical properties, making them attractive for advanced functional applications. In this study, a systematic investigation of Co2+ and Ni2+-doped LiZnVO4 (LZVO) is presented to elucidate their structural transitions, optical behavior, and potential for energy-efficient coating technologies. A clear miscibility gap is observed in intermediate compositions, indicating limited solid solubility between the two end members. The local lithium environments are probed using magic angle spinning 7Li and 51V solid-state NMR spectroscopy, providing direct evidence for the incorporation of the two paramagnetic dopant ions into the crystal lattice. At low dopant concentrations, the 7Li isotropic peak intensity increases due to paramagnetic relaxation enhancement, whereas higher concentrations lead to characteristic peak broadening. CIELAB color space shows systematic color tuning with increasing dopant concentration: green → brown → black for Co-doping and light greenish yellow → yellow → brown for Ni-doping. Importantly, the doped LZVO-0.02Ni and LZVO-0.02Co compositions exhibit high NIR solar reflectance of 85.7% and 65.2% respectively, in the wavelength range 700–2200 nm, enabling effective solar heat management. The combination of phase-selective doping, tunable color properties, and strong NIR solar reflectivity positions these materials as promising candidates for next-generation cool pigments.

Two tungsten-based oxides, Li2WO4 and h-WO3, were investigated as anode materials for lithium-ion batteries in half-cell configuration (vs. Li) within the voltage window of 3.0–0.05 V. The initial lithiation process in both materials involves Li intercalation into the lattice, followed by a conversion reaction. The Li2WO4 anode exhibited outstanding electrochemical performance, delivering a high reversible capacity of 547 mAh g−1 at 0.1C and 355 mAh g−1 at 1C after 70 cycles. Furthermore, it demonstrated fast charging capability and exceptional cycling stability, maintaining a discharge capacity of 280 mAh g−1 at 5C even after 1500 cycles. In comparison, the h-WO3 anode displayed significantly lower performance under similar conditions. These results highlight that the presence of pre-existing lithium ions in the host lattice of Li2WO4 facilitates efficient lithiation and delithiation, contributing to its superior capacity and extended cycle life. This study underscores the potential of Li2WO4 as a promising anode material for next-generation lithium-ion batteries.

Conventional liquid electrolytes utilized in supercapacitors suffer from leakage, flammability, and poor adaptability making them unsuitable to design flexible, wearable, and portable devices. Despite the significant advancements in designing flexible electrode materials towards the fabrication of safer and integrated energy storage systems, the development of optically transparent and mechanically flexible polysaccharide-based solid-state electrolytes remains comparatively limited. Herein, we report a series of flexible solid-state electrolyte (FSSENaI-x; where x = 27, 43, 53, 60, 65, and 69 wt%) films, composed of konjac glucomannan (KGM), hydroxypropyl methylcellulose (HPMC), and sodium iodide (NaI). Among them, the FSSENaI-65 film exhibits optimal properties in terms of mechanical, optical, and ionic conductivity suitable for designing supercapacitor devices. It achieves a Young's modulus of ∼2.5 MPa with an exceptional elongation at break at 118%, along with an optical transparency of 88% at 800 nm. It delivers a high ionic conductivity of 2.77 mS cm−1 at room temperature and a wide electrochemical stability window of 2.4 V. A solid-state supercapacitor assembled with the FSSENaI-65 film shows a specific capacitance of 159 F g−1 at 1 A g−1, with an excellent cycling stability retaining 87.5% of its specific capacitance over 4000 cycles at 5 A g−1. It maintains a stable performance under bending conditions with a capacitance retention of 72.2% over 2000 cycles at 5 A g−1. The device furnishes a high energy density of 22.1 Wh kg−1 and power density of 500.6 W kg−1 at 1 A g−1 confirming its potential for next-generation flexible energy storage systems.

The increasing demand for high-performance lithium-ion batteries (LIBs) in electric vehicles (EVs) and renewable energy storage systems underscores the need for advanced cathode materials with enhanced energy density, thermal stability, and long-term cycling performance. Nickel-rich cathodes, such as NCM-622, offer high capacity and energy density but suffer from structural degradation, transition metal dissolution, and electrolyte decomposition at elevated voltages and temperatures. In this study, magnesium-doped single-crystalline (SC) NCM-622 cathode material is synthesised using a multi-step annealing process to address these challenges. The Mg2+ doping significantly improves structural stability by suppressing cation mixing, stabilizing the layered structure, and mitigating abrupt lattice distortions. The SC morphology eliminates grain boundary-induced failures, enhancing electrochemical performance and thermal stability. Electrochemical analyses reveal that the Mg-doped SC NCM-622 cathode exhibits superior cyclic stability, retaining 81.7 % of its capacity after 300 cycles at 4.3 V and maintaining performance even at elevated temperatures. This study highlights the effectiveness of Mg2+ doping and SC architecture in addressing the limitations of Ni-rich cathodes, offering a promising approach for developing high-energy-density LIBs for next-generation energy applications.

In this study, we explore the potential of Vigna Mungo (L) Hepper (black gram skin, BGS), an agricultural byproduct, for synthesising high-quality graphite through a catalytic graphitisation process. Using a nickel-catalysed method, we successfully transformed BGS-derived carbon into highly ordered graphite at 1300 °C (BG-1300), with further surface area enhancement achieved via KOH activation (BG-1300-KOH) including X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM), confirmed the formation of highly ordered graphite with a high degree of graphitisation (62.9 %) and crystallite size (9.69 nm). Electrochemical evaluations demonstrated the potential of BGS-derived graphite as an anode material for lithium-ion batteries (LIBs) and lithium-ion hybrid capacitors (Li-HCs). The BG-1300-KOH sample exhibited a reversible discharge capacity of 610 mAh g−1, outperforming commercial graphite (410 mAh g−1) and pristine BG-1300 (380 mAh g−1). The extent of Na-ion intercalation indicates the degree of disorder in carbon. In this study, as the carbonization temperature increases, the intercalation capacity progressively decreased, reflecting a transition towards more ordered, graphitic carbon. Furthermore, a Li-HC device fabricated with BG-1300-KOH as the anode and nitrogen-phosphorous-doped hard carbon (BGAC-NP) as the cathode achieved a maximum energy density of 175 Wh kg−1 and a power density of 25,000 W kg−1, surpassing many reported carbon-based Li-HC devices. This study highlights the feasibility of converting agricultural waste into high-performance graphite, offering a sustainable pathway for energy storage applications while addressing environmental concerns associated with biomass disposal.

NCM-622 cathodes have been promising cathodes for lithium-ion batteries due to their high reversible specific capacity and low cost. However, the NCM-622 cathode suffers from structural instability, especially at high voltage. Moreover, at elevated voltages and temperatures the cathode suffers from surface side reactions and particle cracks due to the presence of grain boundaries. The in situ doping of Mg2+ is achieved by doping Mg ions during the synthesis procedure using a CSTR and the LiBO2/B2O3 surface coating is achieved by a simple wet-chemistry method; this dual-modification not only protects the surface of the cathode but the Mg2+ ions in the structure also enhance the cycling stability even at high voltage (4.5 V) and temperature (55 °C). As a result, animproved electrochemical behaviour was observed and the cathode could retain 82.5% of its initial capacity after 100 cycles at 4.5 V. Furthermore, the presence of the hybrid coating on the surface protects the cathode from HF attack and reduces the voltage polarisation during high temperature and voltage cycling. Such a dual-modification strategy can be commercially viable and useful for modification of high-energy-density NCM-622 cathodes.

LiFePO4 (LFP) is widely used as cathode material in Li-ion batteries in electric vehicles (EV’s). The theoretical capacity of LFP is 170 mAhg−1. It is difficult to achieve the theoretical capacity value, especially at high C-rates, mainly because of its poor ionic as well as electronic conductivity. Several doping strategies have been adopted of which Mn as well as V doping individually, show beneficial effect in improving the electrochemical performance. However, co-doping of these two ions and the synergistic effect, if any, on the electrochemical performance of LFP has not been explored hitherto. In the present study, Mn and V co-doped LFP cathode materials were synthesized by solvothermal method. Phase formation was confirmed by X-ray diffraction studies, while 7Li MAS NMR spectra revealed changes in isomeric shift (-18.03 ppm for pristine LFP, -1.01 ppm for Mn-doped, and -0.65 ppm for Mn, V co-doped LFP), confirming Mn and V are incorporated into the olivine lattice. The co-doped LFP exhibited a unique two-dimensional morphology with uniform, fluffy particles (~ 3 µm × 2 µm). X-ray photoelectron spectra confirmed the presence of Fe2+, Mn2+, and V4+ oxidation states. The Li-ion diffusion coefficient (DLi+) of Mn and V co-doped LFP (6.93 × 10−15 cm2s−1) was higher than that of pristine LFP (2.97 × 10−15 cm2s−1), indicating enhanced Li-ion diffusion in the co-doped sample. Electrochemical tests in half-cell mode showed that co-doped LFP achieved a 167, 153 and 145 mAhg−1 capacity at 0.1, 1.0, and 2.0 C-rates, respectively. Inaddition, the co-doped composition showed excellent capacity retention, even at high C-rates i.e., 135 mAhg−1 with 90% retention after 500 cycles at 1C and 101.3 mAhg-1 with 70% retention after 1000 cycles at 2C. Also, the co-doped phase exhibited lower polarization and charge transfer resistance, highlighting its potential for high-performance lithium-ion batteries.

The increasing global demand for energy solutions has created the necessity for innovative nanocomposite materials for efficient energy storage applications. This urgency is driving significant advancements in energy storage technologies, raising hope for the future of energy sectors. Supercapacitors (SCs), high-performance electrochemical storage devices, have earned considerable attention to address these challenges. In this article, we have demonstrated a cost-effective, easily obtainable trimetallic spinel/defect-spinel oxide ZnMn2O4/Cu1.5Mn1.5O4 (ZMO/CMO) nanocomposite through a facile one-step solvothermal synthesis process. This nanocomposite demonstrated exceptional charge storage capabilities. The charge storage mechanism was established by using Dunn’s method, which reveals the diffusive nature of the electrode material. The ZMO/CMO nanocomposite exhibits an impressive specific capacitance of 468.1 F/g at 0.5 A/g, with 84% capacity retention even after 20000 cycles, which was attributed to the oxygen vacancies within the defect spinel structure. Moreover, we fabricated an asymmetric device utilizing ZMO/CMO as the cathode and activated carbon (AC) as the anode. This device attained an energy density of 48.1Wh/kg and a power density of 700 W/kg with excellent cycling stability, as mentioned before. Furthermore, our study featured its ability to power a standard LED light.

Green Hydrogen emerges as a promising energy solution in the quest for achieving Net Zero goals. The application of particulate semiconductors in photocatalytic water splitting introduces a potentially scalable and economically viable technology for converting solar energy into hydrogen. Overcoming the challenge of efficiently transferring photoelectrons and photoholes for both reduction and oxidation on the same catalyst is a significant hurdle in photocatalysis. In this context, we introduce highly efficient crystalline elemental boron nanostructures as photocatalysts, employing a straightforward and scalable synthesis method yield green hydrogen production without the need for additional co-catalysts or sacrificial agents. The resulting photocatalyst demonstrates stability and high activity in H2 production, achieving over 1 % solar-to-hydrogen energy conversion efficiency (>15,000 μmol. g−1.h−1) during continuous 12-h illumination. This efficiency is credited to broad optical absorption and the crystalline nature of boron nanostructures, paving the way for potential scale-up of reactors using crystalline boron photocatalysts.

Ni-rich cathodes are very attractive in terms of high-energy density cathodes. However, it still suffers from various disadvantages, making commercialization more difficult. A dual-modifying cathode is a simple and efficient strategy that can have a synergistic effect of surface coating on the outside, and doping can have internal structure stabilization. CSTR-level doping of Mg2+ can significantly extend the battery’s cycle life due to its pillar effect, and LiNbO3 is a prominent coating material with high ionic conductivity. The dual-modified cathode in this study has shown excellent electrochemical performance in terms of cyclic stability and rate performance, even at 4.5 V vs. Li. The modified cathode showed 85.4% capacity retention at 4.3 V and 87.11% at 4.5 V, whereas the bare showed only 78.9% and 68.2%, respectively. The LiNbO3-coating protects the material from the surface side reactions from the electrolytes at high voltage operations, and the “pillar effect” due to Mg2+ doping stabilizes the structure for longer cycles and higher C-rates, making this dually modified cathode a prominent cathode material for lithium-ion batteries. Graphical abstract: (Figure presented.)

Biomass-derived activated carbon materials have been attracted as low-cost and sustainable electrode materials for energy storage applications. In this work, we synthesised activated carbon from black gram whole skin for the first time, and the used source is a cost-effective carbon precursor. Nitrogen and phosphorous doping in activated carbon improved electronic conductivity, surface area and porosity. In supercapacitor application, the nitrogen and phosphorous doped activated carbon sample showed a high specific capacitance of 425 F g−1 at 0.5 A g−1 and cycling stability of about 92.5 % capacitance retention even after 5000 cycles in a three-electrode system. The observed stable specific capacitance in a three-electrode system encouraged us to make a two-electrode symmetric device, showing a specific capacitance of 100 F g−1 at 0.5 A g−1 with a higher energy density of 20 Wh kg−1. In addition, the lithium storage capability of doped carbon showed good capacity of 750 mAh g−1 at 0.1 A g−1 with a reversible capacity of 687 mAh g−1 after 100 cycles. The hetero-atom doped activated carbon derived from black gram skin showed outstanding electrochemical performance towards supercapacitor and lithium battery application, indicating a potential alternative to fossil fuel-derived carbon.

Emerging novel 2D materials with unique electrochemical properties generate massive interest among researchers to fabricate the supercapacitors with high energy density without fading actual power density. In present work, a novel 2D Bismuthene-Molybdenum disulfide composite (Biene-MoS2 NC) was synthesized which serves as an effective active material for the fabrication of electrodes for supercapacitors with superior electrochemical characteristics. The synthesized Biene-MoS2 NC electrode provides the improved specific capacity of 195.9 mAh/g at the sweep rate of 10 mV/s together with the total stored capacity, outer surface adsorption capacity, and intercalation capacity of 285, 10.8, and 274.2 mAh/g respectively and their percentage of capacitance and diffusion of 36.3 % and 63.7 % respectively. The pouch type supercapacitor cell was fabricated using Biene-MoS2 NC as positive electrode (cathode) and activated carbon (AC) as negative electrode (anode) which demonstrated high areal capacitance of 38.2 mF/cm2 at the current density of 0.5 mA/cm2 and also it delivered the enhanced areal energy and power densities of 11.94 μWh/cm2 and 1 mW/cm2 respectively.

Dual-modified Zr4+-doped and ZrO2-coated NCM-622 with excellent electrochemical properties was synthesized by simple wet-chemical coating. X-ray diffraction analysis revealed the unit cell expansion along the c-direction in the Zr-modified sample, which was substantial in improving the lithium-ion kinetics. The surface coating of ZrO2 was visible in TEM images protecting the cathode from surface-side reactions. The electrochemical performance of the Zr-modified sample was superior to that of the other modified and uncoated samples; it showed higher cyclic stability even after 100 cycles at a 1C rate and offers 86.3% capacity retention, whereas the unmodified sample yielded only 21.7% of its initial capacity. Zr4+ doping acts as a pillar, stabilizing the structure to provide better Li+ diffusion and increased cyclability and rate capability. Further analysis showed that the Zr-modification has shown superior electrochemical performance and cyclic stability even at elevated temperatures of 55 °C. The ZrO2 coating on the surface can act as an HF scavenger during cycling at high temperatures. The superior cycling stability and rate capability can be attributed to the synergetic effect of simultaneous doping and coating of zirconia on the NCM-622. Graphical abstract: [Figure not available: see fulltext.].

In this study, we developed the MoS2-MgOH2-BiVO4 hybrid via the hydrothermal technique for counter electrode (CE) of dye-sensitized solar cells (DSSC). The prepared samples were confirmed by XRD and FTIR analysis. The optical studies were done by ultraviolet–visible spectra, which confirmed the narrowing bandgap of the MoS2-Mg(OH)2-BiVO4 hybrid. The morphological structure of MoS2 nanorods was turned into MoS2-Mg(OH)2-BiVO4 ternary hybrid hierarchical nanosheets that coexisted with particles. The MoS2-MgOH2-BiVO4 counter electrode and commercial TiO2 photoanode were utilized for constructing the DSSC solar cell. According to the photovoltaic responses of the DSSC, the ternary square-like MoS2-MgOH2-BiVO4 hierarchical nanosheets were 1.48 times more effective than pure MoS2. The charge transfer mechanism of ternary hybrid photovoltaic was investigated and discussed.

Biomass-derived carbon showed much promise as it eliminates fossil fuel dependency and has several other advantages, such as being renewable, abundant, and environmentally friendly. In the present study, activated carbon is derived from foetida biomass using a single-step synthesis method. Nitrogen-doping studies were carried out to improve the electronic conductivity and found that the 1:0.5 weight ratio of carbon to nitrogen source is a critical composition which exhibited improved electronic conductivity without losing substantial surface area and porosity. The critical composition showed outstanding electrochemical performance versus Li-metal, with a reversible discharge capacity of 423 mAh/g at 0.1A/g current density. Also, it showed good cycling stability, 310 mAh/g after 100 cycles at 0.1A/g current density. The nitrogen-doped activated carbon material has the potential to be used as anode material in rechargeable Li-ion batteries.

In our ecologically concerned world, the growing demand for energy to support human needs presents an increasing issue. The current primary energy source's heavy reliance on fossil fuels not only depletes limited resources but also greatly increases environmental pollution. The solution to this conundrum is a radical move in the direction of sustainable alternatives, of which solar energy is a prime contender because it produces no pollution. It is essential to switch completely to solar energy from conventional energy sources in order to ensure a cleaner and greener future. However, the investigation and implementation of novel systems that smoothly combine solar energy harvesting and storage into a single apparatus. Remarkably, the integration of solar energy conversion and storage systems is still undergoing significant advancements, as the scientific community has recently embarked on exploring this subject. This study investigates a pressing need in modern times: the development of a singular gadget known as “photo-supercapacitors”. The performance and efficiency of the system are thoroughly examined by assessing the crucial factors. The paper provides a thorough overview of the progress made in enhancing the flexibility and efficiency of photo-supercapacitors, offering valuable insights into the promising future of energy systems and technology.

Herein, we report the Li-ion conducting composite material, Li0.57La0.29TiO3 (LLTO), coated on a microporous polyethylene separator to use in rechargeable Lithium-metal batteries. Since the LLTO contains structural Li-ions and the three-dimensional conducting channels within, it not only improved the ionic conductivity of coated separator but also improved the surface electrolyte wettability and suppressed the dendrite formation. As a result, the Lithium-metal battery cycling stability and safety features are increased. Consequently, the ceramic composite separator enabled a specific capacity of 105.6 mAhg−1 for Li/LiMn2O4 coin cell, and 80 % capacity retention is observed even after 500 cycles at 1C, indicating its promising practical potential application. This work provides a feasible and efficient modification strategy of separators for improving the cycling performance and safety of Lithium-metal batteries. In addition, the ceramic composite-coated separator could instill confidence in using Lithium metal as the attractive anode for high-capacity Li-air and Li‑sulfur batteries with enhanced thermal and cyclic stability.

Ever growth in the energy demand has catapulted us to explore various energies. Henceforth, to meet these ends, among the different cathode active materials, nickel (Ni) rich polycrystalline (PC) cathode materials have been known to serve the purpose aptly. Yet, these PC Ni-rich cathode materials have yielded inferior performances with an increase in voltage and temperature. The absence of grain boundaries in the intrinsic structure, high mechanical strength, high thermal stability, and controllable crystal faucet have made SC cathodes a better prospect. Yet, there are challenges to overcome in the SC cathodes, like larger crystals hindering the Li+ transport, which leads to disappointing electrochemical performance. Through this perspective article, we wish to elucidate the crucial factors that facilitate the growth of SC-NCM cathode, viable dopants, and coating materials that could enhance the performance, future scope, and scalability of SC-NCM at the Industrial level.

The oxide-based narrow band red emitting phosphor is critical and assumes a fundamental part to upgrade the overall efficiency of the white LED. In this regard, a series of Eu3+-activated Na2La4(WO4)7 (NLW) red emitting phosphors were synthesized employing a solid state approach, and we examined their optical properties in detail. All of the compositions crystallize in tetragonal structure with a I41/a space group. Sharp red emission was exhibited by all the NLW:Eu3+ phosphors ~616 nm owing to the ED transition (5D0 → 7F2), under the excitation of 394 nm and observed concentration quenching when x = 0.8. In addition, color purity and IQE of Na2La3.2(WO4)7:0.8Eu3+ phosphor is found to be 96.79% and 83.76%, respectively. A temperaturedependent PL study reveals the thermal stability of the phosphor as 69.75% at 423 K. Red and white LEDs were fabricated utilizing the synthesized phosphor to understand their practical applicability. EL spectra of the red LED displayed intense red emission, whereas white LED exhibited warm white light with high CRI (80) and low CCT (5730K) values. These Eu3+-doped red phosphors can also be used for latent fingerprint application. Moreover, a series of Sm3+ and simultaneous activation of both Sm3+ and Eu3+ in NLW phosphors were synthesized, and investigated their optical properties. By using the Sm3+-codoped Eu3+-activated phosphor, a red/deep red LED is fabricated for the plant growth purpose. These outcomes suggested that the synthesized phosphors could be promising phosphors for the WLED, security, and plant growth applications.

Advanced two dimensional nanostructures with distinctive physicochemical properties, excellent surface chemistry, and adjustable interlayer band-gap enhances the electrochemical activity in the field of supercapacitors. This work focuses on the formation of the hybrid nanocomposite of Bismuthene-Multiwall carbon nanotube nanocomposite (Biene-MWCNT NC) to enhance the electrochemical activity. Cyclic Voltammetry (CV) analysis of Biene-MWCNT NC reveals the enhanced specific capacity of 323.65 C/g at the scan rate of 10 mV/s. In addition, the Trasatti method shows the charge accumulation mechanism which delivering the total, inner, and outer capacity of 662.3, 601.02, and 61.23 C/g respectively together with the capacity and diffusion contribution percentages of 90.76 % and 9.24 % correspondingly. Furthermore, Biene-MWCNT//MWCNT hybrid supercapacitor (HSC) demonstrates the elevated specific capacity of 113.85 C/g at the constant current density of 0.5 A/g and the outstanding energy density of about 35.5 Wh/kg corresponds to high power density of 11250 W/kg.

The recent surge of research in the development of sodium-ion batteries (SIBs) as an alternative to the lithium-ion batteries (LIBs) has shown that the SIBs can reduce the load of the LIBs in certain areas. However, the development of SIBs in the commercial arenas is yet to be tapped. This perspective delineates the importance of Ni-rich cathodes and various strategies to ameliorate the performance of the Ni-rich cathodes in the SIBs. Also, discussed various synthesis routes for the industrial-scale synthesis of Ni-rich materials and tried to elucidate the importance of SC cathodes and the necessity to develop those in SIBs.

A comprehensive understanding of lithium-ion batteries became an essential aspect of solid-state electrochemical research due to their coalescence with routine. While it exhilarates us with increase in productivity of LIBs due to the emergence of Ni-rich cathode materials, the scope to upscale it according to the industrial needs is yet to be tapped to its full potential. Through this perspective article, the functional differences between LIBs and SIBs, state-of-the-art Single-crystalline NCM cathode, the status of the respective research works, crucial factors for industry scaling of the cathode materials, and the future scope of the research work are elucidated.

Pure and Mn-doped ZrO2 nanocrystals (Zr1-xMnxO2) with varying Mn concentrations (x ​= ​0.02, 0.04, 0.06, and 0.08) have been synthesized using sol-gel method. The effect of Mn doping concentration on structural, optical and magnetic properties has been investigated. X-ray diffraction data and SAED analysis revealed that all Zr1-xMnxO2 nanocrystals have a tetragonal structure without any secondary phase. The average crystallite size obtained from XRD decreases (within the experimental uncertainty) with increased Mn concentration. Magnetic measurements have revealed that Zr0.98Mn0.02O2 nanocrystalline sample exhibits both low and room temperature ferromagnetism. The origin of ferromagnetism is attributed to the anionic vacancies created due to Mn doping in ZrO2. Higher Mn concentrations shows superparamagnetism whereas pure ZrO2 displayed diamagnetic behavior. The UV–Vis absorption spectra showed a wide absorption peak at 200–330 ​nm, and a redshift was observed in the bandgap with an increase in the concentration of Mn2+.

A combination of surface area analyzer and microcalorimetry was employed to investigate the in situ water uptake energetics and the mechanism of proton incorporation in yttrium-doped barium zirconate in the temperature range 200-400 °C. The BaZr1-xYxO3 solid solutions are made with variable yttrium content (x = 10, 20, and 30 mol %) by a controlled oxidant-peroxo synthesis method. The water uptake increases as the partial pressure of water increases; however, no saturation in the hydration isotherm is observed, implying further reaction at higher pH2O. The results suggest three distinct regions of hydration energies as a function of water content. The first water uptake enthalpy values showed high exothermicity, -140, -158, and -157 kJ mol-1 for BaZr1-xYxO3 (x = 10, 20, and 30 mol %), respectively, at 400 °C, and the strong exothermic contribution supports the dissociative incorporation of water. The stepwise in situ hydration energetics is essential to understand the mechanisms of water incorporation and the role of H2O uptake in transport properties.

Hydrothermal method successfully produced a new cesium-metal borate (CsKB4O5(OH)4·2H2O). The crystals are grown in the P21/c space group with a monoclinic lattice, a = 10.7298 (13) Å, b = 8.1521 (11) Å, c = 13.2690 (15) Å, _ = 108.325 (9)°, and Z = 4. The structure is composed of [B4O5(OH)4]2− groups connected to 8-coordinated potassium, 12- oordinated cesium ions, and water molecules forming the final 3D framework. FTIR and Raman spectra identified the type and nature of the borate groups within the structure. UV-Vis- NIR diffuse reflection spectra have studied the transmission property, whereas TG-DSC analyses revealed the thermal stability of the crystals. In addition, theoretical calculations have been executed to understand the density of states and band structure.

In the present work numerous compositions of Er-doped SnO2 thin films were made at 425 °C on a quartz glass substrate using spray pyrolysis method. The powder X-ray diffraction and X-ray photoelectron spectroscopy analysis confirms the tetragonal phase and surface chemical composition of as made Sn1-xErxO2 (x = 0.0, 0.01, 0.02, 0.03, 0.04, and 0.05) thin films. The grain size and RMS roughness of the films were estimated from the AFM measurements and the film surface has a saw-tooth-like morphology. The transmission spectra of the films are fallen in the visible range having between 60% and 80% transmittance with different Er concentration. The optical direct, indirect band gap and phonon energy values have been estimated. The photoluminescence measurements under excitation at 325 nm show three distinct emission peaks, a broad hump positioned at 390 nm, two sharp peaks at 420 nm related to tin interstitials, and a sharp peak at 700 nm related to oxygen vacancies. The Er3+ in SnO2 increased the oxygen vacancies to maintain charge balance and as a result the intensity of emission peaks increases with Er content.

The formation thermodynamics of YBaCo 4-x Zn x O 7+δ (x = 0, 1, and 3) oxides was determined by high-temperature oxide melt solution calorimetry. All of the studied oxides are thermodynamically metastable due to the tendency of cobalt to increase the oxidation state under oxidizing conditions as well as to significant bond valence sum mismatch for Ba and Y in 114-oxides. Complex phase evolution in YBaCo 4 O 7+δ at 350-400 °C upon oxygen absorption was revealed using incremental precise oxygen dosing. The calorimetric results support phase changes seen during in situ X-ray diffraction structural studies and provide high-resolution measurement of the amount and energetics of oxygen absorbed by YBaCo 4-x Zn x O 7+δ under equilibrium conditions.

Pyrochlore, an ordered derivative of the defect fluorite structure, shows complex disordering behavior as a function of composition, temperature, pressure, and radiation damage. We propose a thermodynamic model to calculate the disordering enthalpies for several RE2Zr2O7 (RE = Sm, Eu, Gd) pyrochlores from experimental site distribution data obtained by in situ high temperature synchrotron X-ray diffraction. Site occupancies show a gradual increase in disorder on both cation and anion sublattices with increasing temperature and even greater disorder is achieved close to the phase transition to defect fluorite. The enthalpy associated with cation disorder depends on the radius of the rare earth ion, while the enthalpy of oxygen disordering is relatively constant for different compositions. The experimental data support trends predicted by ab initio calculations, but the obtained enthalpies of disordering are less endothermic than the predicted values. Thermal expansion coefficients are in the range (8.6-10.8) × 10-6 K-1. These new experimental determinations of defect formation energies are important for understanding the stability of pyrochlore oxides and their disordering mechanisms, which are essential in the context of their potential applications in nuclear waste management and other technologies.

The oxidation of boride and carbide-based ultra-high-temperature ceramics is the primary limiting factor for their use as aerodynamic surfaces. Understanding the behaviour of the oxides that can result from oxidation of metal borides and carbides at very high temperatures is essential to optimise and tailor the performance of these materials; yet experimental thermodynamic and structural data for refractory oxides above 2000°C are mostly absent. The following techniques that can be applied to fill this gap are discussed: (i) commercial ultra-high-temperature differential thermal analysis for investigation of phase transformations and melting in inert environments to 2500°C, (ii) a combination of laser heating with a splittable nozzle aerodynamic levitator for splat quenching and drop calorimetry from temperatures limited only by sample evaporation, (iii) synchrotron X-ray and neutron diffraction on laser-heated aerodynamically levitated oxide samples for in situ observation of phase transformations in variable atmospheres, refinement of high-temperature structures and thermal expansion. Recent experimental findings include anomalous thermal expansion of the defect fluorite phase of YSZ, thermodynamics of pyrochlore–fluorite transformation from high-temperature structure refinements, and measurement of thermal expansion to the melting temperatures and fusion enthalpies of Zr, Hf, La, Yb and Lu oxides. These methods provide temperatures, enthalpies and volume change for phase transformations above 2000°C, which are required for thermodynamic assessments and calculation of phase diagrams of multicomponent systems.

Perovskite-structured lithium lanthanum titanate (LLTO) Li3xLa0.67-xTiO3 (compositions x = 0.04 to 0.15) has been prepared by conventional solid state reaction. The phase purity and crystal structural changes were investigated with XRD, FTIR and Raman. The vibrational spectra reveal the interaction between metal cation and oxygen anion with increasing Li doping and structural evolution. LLTO and component oxides were studied by high temperature oxide melt solution calorimetry. The formation enthalpies of LLTO from oxides are exothermic for all compositions, indicating thermodynamic stability. There are two regimes in the trend of formation enthalpy with increasing Li concentration. In the first regime, x ≤0.08, the formation enthalpies vary slowly with composition, but the lowest stability by about 1.5 kJ mol-1 is seen at x = 0.06. An abrupt change in the formation enthalpy trend is observed in the second regime when x ≥0.1, where maximum lithium ion conductivity (at x = 0.10) is reported. The least stable composition, x = 0.06, occurs where maximum charge carrier concentration and lowest activation energy is reported. From the thermodynamic study, it is clear that the energetically least stable composition correlates with lowest activation energy whereas the sharp change in formation enthalpy trend correlates with highest Li-ion conductivity.

Yttrium-doped barium zirconate ceramic powders were synthesized by the oxidant peroxide method in air and under controlled atmosphere of nitrogen inside a glove box. The powders were characterized by thermogravimetry, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. After uniaxial cold isostatic pressing, green pellets were sintered at 1600 °C for 4 h. The electrical conductivity behavior was accessed by electrochemical impedance spectroscopy. The results show that specimens synthesized under controlled atmosphere achieved higher electrical conductivity, two orders of magnitude higher than specimens prepared in laboratory air. The enhancement in electrochemical properties and increase in sintering ability is attributed to the less carbonate contamination as a result lower grain boundary density in the samples prepared under controlled atmosphere.

High-temperature oxide melt solution calorimetry using sodium molybdate (3Na2O·4MoO3) solvent at 973 K was performed for the Na3xRE0.67-xTiO3 (RE = La, Ce) perovskite series. The enthalpies of formation of lanthanum perovskites from oxides (La2O3, Na2O, TiO2), are -107.25 ± 2.56, -93.83 ± 6.06, -80.68 ± 5.93, and -33.49 ± 4.26 kJ/mol and enthalpies of formation from elements are -1614.05 ± 5.37, -1596.44 ± 7.68, -1594.03 ± 7.58, and -1577.56 ± 6.36 kJ/mol for Na0.459La0.522Ti0.999O3, Na0.454La0.523Ti0.994O3, Na0.380La0.567Ti0.980O3, and La0.692Ti0.979O3, respectively. The enthalpies of formation of cerium perovskites are -99.98 ± 5.78 and -45.78 ± 3.30 kJ/mol from oxides (Ce2O3, Na2O, TiO2), and -1611.34 ± 6.90 and -1602.06 ± 2.72 kJ/mol from elements for Na0.442Ce0.547Ti0.980O3 and Ce0.72Ti0.96O3. The A-site defect perovskites become more stable relative to oxide components as sodium contents increase. Na0.5Ce0.5TiO3 and Na0.5La0.5TiO3 could be considered as thermodynamically stable end-members in natural loparite minerals, in which these end-members are in solid solution with CaTiO3 and other components.

In the context of evolving market conditions, the three-way catalyst (TWC) design is entering an exciting new phase. It remains the main emission control strategy for gasoline powered vehicles; in the meantime a rapid period of evolving engine developments, the constrained tailpipe regulations and the material supply issues present a unique challenge to the catalyst developers. A key approach here is to achieve highly beneficial emission performance based on the ultra-low PGM levels. In this regard, we mainly focus on the materials design and have developed the advanced spinel oxides for zero precious metals (ZPGM) and synergized precious metals (SPGM) TWCs. These advanced spinel materials showed improved thermal stability compared to that of PGM based standard materials. Fundamental studies on the microstructure of spinel oxide with newly developed composition confirm the aging stability. The vehicle test data are reported for 10 g/ft3 SPGM close-coupled (CC) and 2 g/ft3 SPGM Underfloor (UF) catalysts based on the advanced spinel material. Prior to testing on tier2 bin 4 turbo gasoline direct injection (TGDi) vehicle using FTP and US06 drive cycles, the tested SPGM CC and UF catalysts are aged under standard 4-mode aging cycle. Our initial data show that SPGM UF performs as effectively as the standard high PGM technology UF catalyst, with lower weighted tailpipe NOx. In addition, SPGM CC catalyst with the low PGM loading (10 g/ft3) performs as effectively as the standard high PGM (>100 g/ft3) technology CC catalyst for NOx and CO conversions, but leaving a room for the improvement of non-methane hydrocarbon (NMHC) conversion performance.

The accurate determination of structure and thermal expansion of refractory materials at temperatures above 1500°C is challenging. Here, for the first time, we demonstrate the ability to reliably refine the structure and thermal expansion coefficient of oxides at temperatures to 2200°C using in situ synchrotron diffraction coupled with aerodynamic levitation. Solid solutions in the Eu2O3-ZrO2 binary system were investigated, including the high-temperature order-disorder transformation in Eu2Zr2O7. The disordered fluorite phase is found to be stable above 1900°C, and a reversible phase transition to the pyrochlore phase is noticed during cooling. Site occupancies in Eu2Zr2O7 show a gradual increase in disorder on both cation and anion sublattices with increasing temperature. The thermal expansion coefficients of all cubic solid solutions are relatively similar, falling in the range 8.6-12.0 × 10-6C-1. These studies open new vistas for in situ exploration of complex structural changes in high-temperature materials.

The role of sensitization by co-doping Ce3+/Eu2+ in the Sr2SiO4:Dy3+ phosphor system is studied with a view of improving the emission properties and chromaticity coordinates. The concentration dependence of the emission intensity of Dy3+ in Sr2-2xDyxLixSiO4: (x=0.01-0.05 in steps of 0.01) is studied, and the critical concentration is found to be 3 mol% Dy3+ per formula unit. Partial energy transfer from Ce3+ to Dy3+ is observed, and the luminescence intensity of Dy 3+ is enhanced. It is also found that Eu2+, Ce 3+ containing compositions show better white emission than the corresponding Sr2SiO4:Dy3+. LEDs fabricated by coating the ultraviolet (UV) emitting chips with the synthesized phosphor compositions show bright white emission with reasonable chromaticity coordinates. © 2013 Elsevier B.V.

The enthalpies of formation from binary oxide components at 25 °C of Ba(Zr1-xYx)O3-δ, x = 0.1 to 0.5 solid solutions are measured by high temperature oxide melt solution calorimetry in a molten solvent, 3Na2O·4MoO3 at 702 °C. The enthalpy of formation is exothermic for all the compositions and becomes less negative when increasing yttrium content from undoped (-115.12 ± 3.69 kJ mol-1) to x = 0.5 (-77.09 ± 4.31 kJ mol-1). The endothermic contribution to the enthalpy of formation with doping content can be attributed to lattice distortions related to the large ionic radius difference of yttrium and zirconium and vacancy formation. For 0.3 ≤ x ≤ 0.5, the enthalpy of formation appears to level off, consistent with an exothermic contribution from defect clustering. Raman spectra indicate changes in short range structural features as a function of dopant content and, suggests that from x = 0.3 to 0.5 the defects begins to cluster significantly in the solid solution, which corroborates with the thermodynamic data and the drop-off in proton conductivity from x > 0.3. This journal is

To provide a complete picture of the energy landscape of Al 2O3 at the nanoscale, we directed this study toward understanding the energetics of amorphous alumina (a-Al2O 3). a-Al2O3 nanoparticles were obtained by condensation from gas phase generated through laser evaporation of α-Al2O3 targets in pure oxygen at25 Pa. As-deposited nanopowders were heat-treated at different temperatures up to 600 C to provide powders with surface areas of 670-340 m2/g. The structure of the samples was characterized by powder X-ray diffraction, transmission electron microscopy, and solid-state nuclear magnetic resonance spectroscopy. The results indicate that the microstructure consists of aggregated 3-5 nm nanoparticles that remain amorphous to temperatures as high as 600 C. The structure consists of a network of AlO4, AlO5, and AlO6 polyhedra, with AlO5 being the most abundant species. The presence of water molecules on the surfaces was confirmed by mass spectrometry of the gases evolved on heating the samples under vacuum. A combination of BET surface-area measurements, water adsorption calorimetry, and high-temperature oxide melt solution calorimetry was employed for thermodynamic analysis. By linear fit of the measured excess enthalpy of the nanoparticles as a function of surface area, the surface energy of a-Al2O3 was determined to be 0.97 ± 0.04 J/m2. We conclude that the lower surface energy of a-Al2O3 compared with crystalline polymorphs γ- and α-Al2O3 makes this phase the most energetically stable phase at surface areas greater than 370 m2/g. © 2013 American Chemical Society.

The surface enthalpies of nanocrystalline CaTiO3 and SrTiO 3 perovskites were determined using high-temperature oxide melt solution calorimetry in conjunction with water adsorption calorimetry. The nanocrystalline samples were synthesized by a hydrothermal method and characterized using powder X-ray diffraction, FTIR spectroscopy, and Brunauer-Emmett-Teller surface area measurements. The integral heats of water vapor adsorption on the surfaces of nanocrystalline CaTiO3 and SrTiO3 are -78.63 ± 4.71 kJ/mol and -69.97 ± 4.43 kJ/mol, respectively. The energies of the hydrous and anhydrous surfaces are 2.49 ± 0.12 J/m2 and 2.79 ± 0.13 J/m2 for CaTiO3 and 2.55 ± 0.15 J/m2 and 2.85 ± 0.15 J/m2 for SrTiO3, respectively. The stability of the perovskite compounds in this study is discussed according to the lattice energy and tolerance factor approach. The energetics of different perovskites suggest that the formation enthalpy becomes more exothermic and surface energy increases with an increase in ionic radius of the "A" site cation (Ca, Sr, and Ba), or with the tolerance factor. PbTiO3 shows a lower surface energy, weaker water binding, and a less exothermic enthalpy of formation than the alkaline-earth perovskites. © 2013 The American Ceramic Society.

Water adsorption on the surface of LiCoO2 nanoparticles was investigated. As the water coverage increases the adsorption enthalpy decreases reaching the enthalpy of water condensation (-44kJ mol-1). The experimentally observed average surface energy corresponding to all facets agree well with those reported from DFT calculations. The observed low surface energy is attributed to the surface Co3+ spin transition in nanophase LiCoO2. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The energetics of the order-disorder phase transformation in the binary oxide system, Eu 2O 3-ZrO 2, is studied by powder X-ray diffraction and high temperature drop solution calorimetry. The nanocrystalline defect fluorite phase of Eu 2Zr 2O 7 is synthesized on crystallization of an amorphous precursor from aqueous precipitation. The defect fluorite transforms to an ordered pyrochlore above 1200 °C. Aerodynamic levitation combined with laser heating is used to prepare coarse defect fluorite, which is otherwise impossible by conventional synthesis techniques. Formation enthalpies from oxides are -62.4 ± 2.6 and -24.6 ± 3.7 kJ mol -1 for the pyrochlore and defect fluorite phase, respectively. The transformation enthalpy from pyrochlore to defect flourite in the coarse sample is 37.8 ± 3.1 kJ mol -1 at 25 °C. The enthalpy of water vapor adsorption on the surface of the nanocrystalline defect fluorite Eu 2Zr 2O 7 is -75 ± 2.5 kJ mol -1 H 2O for coverage of 9.5 ± 0.8 H 2O/nm 2. The calculated surface enthalpies for the anhydrous and hydrous surfaces of defect fluorite Eu 2Zr 2O 7 are 1.47 ± 0.13 and 1.01 ± 0.15 J m -2, respectively. © 2012 The Royal Society of Chemistry.

To explore the surface properties of perovskites with ions of different bond character, the surface and interface enthalpies of nanocrystalline PbTiO 3 and BaTiO 3 perovskites were determined for the first time by a combination of calorimetric, morphological, and structural analyses. PbTiO 3 and BaTiO 3 nanocrystalline samples of varying surface areas and degrees of agglomeration were synthesized by solvothermal and hydrothermal methods, respectively. All synthesized samples were characterized using X-ray diffraction and Raman spectroscopy. Interface areas were estimated by comparing the surface areas measured by N 2 adsorption to the crystallite sizes refined from X-ray diffraction data. The integrated heats of water vapor adsorption on the surfaces of the nanocrystalline phases are-62 ± 4 kJ/mol for PbTiO 3, which is less exothermic than the value-72 ± 9 kJ/mol for the isostructural BaTiO 3, both phases having the same chemisorbed water coverage. Similar behavior is observed for the surface and interface enthalpies. The energies of the hydrous and anhydrous surfaces are 1.97 ± 0.67 J/m 2 and 1.11 ± 0.23 J/m 2 for PbTiO 3, and 3.69 ± 0.22 J/m 2 and 3.99 ± 0.28 J/m 2 for BaTiO 3, respectively. The interface energies of the hydrous and anhydrous surfaces are 0.55 ± 0.74 J/m 2 and 0.73 ± 0.27 J/m 2 for PbTiO 3, and 1.11 ± 0.13 J/m 2 for BaTiO 3. These observations suggest that PbTiO 3 has lower surface energy and lower affinity for water adsorption on the surface than BaTiO 3 and that surface energy and hydrophilicity of the surface decrease with increasing covalent character of the ions, as was seen previously in comparing TiO 2 and SnO 2. © 2012 The American Ceramic Society.

A new series of gallozincates LnBaZn3GaO7 (Ln=La, Nd, Sm, Eu, Gd, Dy, Y) and new aluminozincates LnBaZn3AlO7 (Ln=Y, Eu, Dy) have been synthesized. Their structure refinements show that these phases belong to the "114" series, with hexagonal P63mc space group previously described for SmBaZn3AlO7. The photoluminescence study of these oxides shows that the Eu3+ activated LnBaZn3MO7 oxides with Ln=Y, La, Gd; and M=Al, Ga exhibit strong magnetic and electric dipole transitions (multiband emission) which is of interest for white light production. These results also confirm that the site occupied by Eu3+ is not strictly centrosymmetric. The electric dipole transition intensity is the highest in GdBaZn3MO7 [M=Al, Ga]: 0.05Eu3+ as compared with other Eu3+ activated compositions. This is due to the layer distortion around GdO6 octahedra when compared with YO6 and LaO6 octahedra. © 2009 Elsevier Inc. All rights reserved.

In the present work, we have synthesized maleevite mineral phase BaB 2Si2O8 for the first time, which is isostructural with the pekovite mineral SrB2Si2O 8. In these europium doped host lattices, we observed the partial reduction of Eu3 to Eu2 at high temperature during the synthesis in air. Tb3 co-doping in MB2Si2O 8:0.01(Eu3/Eu2) [M=Sr, Ba] improves the emission properties towards white light. The emission color varies from bluish white to greenish white under UV lamp excitation when the host cation changes from Sr to Ba. © 2010 Elsevier Inc. All rights reserved.

The synthesis of a mixed valent LixEuII xEuIII0.33-xZr2(PO4) 3 with the NZP structure, using soft chemistry was reported. Stoichiometric amounts of starting materials Eu2O3 and ZrOCl2.8H2O were dissolved in 2 N HNO3, addition of NH4H2PO4 to the metal nitrate solution under constant stirring resulted in a colorless gel. Electrochemical lithium insertion studies were carried out by using Swagelok type cells with lithium metal as the negative electrode. The mixture was pressed onto a stainless steel plate to form the electrode. The photoluminescence (PL) spectrum of the reduced phase shows signature of both Eu3+ and Eu 2+ excitation and emission bands. It was observed that The CIE coordinates are significantly changed upon Li insertion and shift towards the white region as the concentration of Li increases in the host.

A new hydrogenophosphate Mn(H2PO4)2 has been synthesized from an aqueous solution. Its ab initio structure resolution shows that the original layered structure of this phase consists of PO 2(OH)2 tetrahedra and MnO5OH octahedra, sharing corners to form [MnP2O8H4]∞ layers, whose cohesion is ensured through hydrogen bonds. The excitation and emission spectra of this phase are characteristic of Mn2+ species. This phosphate is shown to be a good protonic conductor with a conductivity of 10-4.4 S/cm at 90°C (363 K). © 2008 American Chemical Society.

A series of Eu2+-activated Li2SrSiO4 orange-yellow phosphor compositions exhibiting intense emission under 400-470 nm excitation are synthesized by solid-state reaction, and their luminescence properties are investigated as a function of activator concentration (Eu 2+). The critical concentration is found to be 0.005 mol of Eu 2+ (Rc = 34 Å) per formula unit. The composition containing 0.005 mol of Eu2+ is also synthesized by a combustion technique followed by postannealing at different temperatures. The luminescence emission intensity of a combustion-synthesized sample increases with increasing annealing temperature. This is attributed to increased crystallinity and improved distribution of activator in the lattice in the combustion-synthesized sample. Attempts are made to develop white light-emitting diodes by combining an InGaN blue LED chip (420 nm) and a Li2SrSiO4: Eu 2+ phosphor. Two distinct emission bands from the InGaN and Li 2SrSiO4:Eu2+ (562 nm) are observed that combine to give a spectrum that appears white to the naked eye. The values of the CIE coordinates indicate that the Li2SrSiO4:Eu 2+-coated LED has improved red emission compared to the commercial YAG:Ce phosphor. © 2006 American Chemical Society.