Synthesis and study of Cd0.5 + x M x Zr2‒x (PO4)3 (M = Mg, Co, Mn) phosphates

Abstract

New phosphates Cd0.5 + xMxZr2‒x(PO4)3 (M = Mg, Co, Mn) have been prepared by sol–gel method. The formation of limited solid solutions Cd0.5 + xMxZr2‒x(PO4)3 of the NaZr2(PO4)3 (NZP) structural type, 0 ≤ x ≤ 0.6 for М = Mg and 0 ≤ х ≤ 0.3 for M = Co and Mn, has been found using X-ray diffraction, IR spectroscopy, and electron microprobe analysis. The distribution of cations in the 2+ oxidation state over crystallographic positions of the NZP structure has been shown in the phosphate CdMg0.5Zr1.5(PO4)3. It has been found that half of framework-forming octahedral positions in the structure of the latter are occupied by Zr4+ cations and the other half are randomly occupied by Zr4+ and Cd2+ ions. The Cd2+ and Mg2+ ions alternately occupy the positions of structure cavities. The thermal expansion of CdMg0.5Zr1.5(PO4)3 in a temperature range of 25‒800°C has been studied. The phosphate is found to be among the medium expanding substances.