Study of calcium-containing orthophosphates of NaZr{sub 2}(PO{sub 4}){sub 3} structural type by high-temperature X-ray diffraction

• Published in: Crystallography reports 2013-03, Vol.58 (2)
• Main Authors: Orlova, A. I., Kanunov, A. E., Samoilov, S. G., Kazakova, A. Yu, Kazantsev, G. N.
• Format: Article
• Language: English
• Subjects: ANISOTROPY; CALCIUM; CATIONS; CRYSTALS; HEAT TREATMENTS; INFRARED SPECTRA; MATERIALS SCIENCE; PEAKS; SILICATES; SODIUM PHOSPHATES; SOL-GEL PROCESS; THERMAL EXPANSION; X-RAY DIFFRACTION; ZIRCONIUM PHOSPHATES
• ISSN: 1063-7745; 1562-689X
• DOI: 10.1134/S1063774513020181

Orthophosphates Ca{sub 0.5}Ti{sub 2}(PO{sub 4}){sub 3}, Ca{sub 0.5}Zr{sub 2}(PO{sub 4}){sub 3}, Ca{sub 0.75}Zr{sub 2}(SiO{sub 4}){sub 0.5}(PO{sub 4}){sub 2.5}, and CaMg{sub 0.5}Zr{sub 1.5}(PO{sub 4}){sub 3} (structural type NaZr{sub 2}(PO{sub 4}){sub 3}), having different occupancies of interframework positions by calcium, have been prepared by the sol-gel method with the subsequent thermal treatment of dried gels and investigated by IR spectroscopy and X-ray diffraction. The analytical indexing of X-ray diffraction patterns is performed within the sp. gr. R3{sup -}. High-temperature X-ray diffraction was used to investigate the behavior of the orthophosphates upon heating: thermal expansion in the temperature range of 20-610 Degree-Sign C (up to 500 Degree-Sign C for Ca{sub 0.5}Zr{sub 2}(PO{sub 4}){sub 3}). The coefficients of thermal expansion are calculated from the shift of diffraction peaks. The unit-cell parameters of crystals at different temperatures are determined. The dependences of thermal expansion and its anisotropy on the occupancy of cation M positions by calcium are revealed.