Study of calcium-containing orthophosphates of NaZr2(PO4)3 structural type by high-temperature X-ray diffraction |
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| Authors: | A. I. Orlova A. E. Kanunov S. G. Samoilov A. Yu. Kazakova G. N. Kazantsev |
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| Affiliation: | 17731. Nizhni Novgorod State University, pr. Gagarina 23, Nizhni Novgorod, 603950, Russia
27731. Leipunsky Institute of Physics and Power Engineering, Obninsk, Kaluga oblast, 249033, Russia
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| Abstract: | Orthophosphates Ca0.5Ti2(PO4)3, Ca0.5Zr2(PO4)3, Ca0.75Zr2(SiO4)0.5(PO4)2.5, and CaMg0.5Zr1.5(PO4)3 (structural type NaZr2(PO4)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. $Rbar 3$ . 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°C (up to 500°C for Ca0.5Zr2(PO4)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. |
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