New NZP-phosphates B0.5FeTa(PO4)3 (where B – Ca, Sr, Ba): Synthesis, crystallochemical investigation and thermal expansion

New phosphates with NaZr2(PO4)3 structure of the B0.5FeTa(PO4)3-type (where B—Ca, Sr, Ba) are synthesized and characterized by X-ray diffraction analysis and IR-spectroscopy. The heating behavior of the phosphates is studied using high-temperature X-ray crystallography in the range 15–625 °C. The unit-cell parameters, the coefficients of thermal expansion αa, αc and their thermal expansion anisotropy |αc − αa| of the phosphates under study are determined and the dependences of these characteristics on the nature of cations are established and analyzed.