Synthesis and crystal structure of nanocrystalline phase: Ca1-xMxZr4P6O24 (M = Sr, Ba and x = 0.0-1.0)

The structure of strontium and barium substituted nano crystalline calcium zirconium phosphate (CZP) was determined on the basis of crystal data of solid solutions. It was found that up to 2.42 mol % of strontium and 1.62 mol % of barium could be loaded into CZP formulations without significant changes of the three-dimensional framework structure. The crystal chemistry of Ca1-xMxZr4P6O24 (M = Sr, Ba and x = 0.0-1.0) phases has been investigated using General Structure Analysis System (GSAS) programming. The Sr and Ba substituted CZP phases crystallize in the space group R-3 and Z = 6. Powder diffraction data have been subjected to Rietveld refinement to arrive at a satisfactory structural convergence of R-factors. The unit cell volume and polyhedral (ZrO6 and PO4) distortion increases with rise in the size and mole % of loaded cation in the CZP matrix. The PO4 stretching and bending vibrations in the Infra red (IR) region have been assigned. SEM, TEM and EDAX analysis provide evidence of Sr and Ba in the matrix. (authors)