New phosphates of the formula M3+M4/2+(PO4)3O (M3+ = Bi and La; M2+ = Ca and Sr) are synthesized. The compounds are isostructural with bismuth calcium vanadate, BiCa4(VO4)3O. A nonlinear increase in both the a and c lattice parameters with an increase in strontium content in the solid solution BiCa(4-x)Sr(x)(PO4)3O (x = 1-4.) is observed. The compounds are characterized by infrared spectroscopy. (C) 2000 Academic Press.