Structural study of polymorphism and thermal behavior of CaZr(PO4)2

Abstract

The crystal structure of CaZr(PO 4 ) 2 has been revised by ab initio Rietveld analysis of X-ray powder diffraction data. At room temperature, CaZr(PO 4 ) 2 crystallizes in the orthorhombic space group Pna2 1 (Z = 4). Differential thermal analysis suggests a reversible second order transition at 1000°C confirmed by high temperature XRD analysis that brings out the existence of a high temperature form, very similar to the room temperature one, but more symmetrical (Pnma, Z = 4). Analysis of the crystal parameters evolution during heating reveals that CaZr(PO 4 ) 2 exhibits a quite low thermal expansion coefficient of 6.11 10 -6 K -1 .This value stems from a combination of several mechanisms, including Coulombic repulsion and bridging oxygen rocking motion.Keywords: Crystal structure; thermal expansion; calcium zirconium phosphate Highlights:Room temperature structure CaZr(PO 4 ) 2 was revised A high temperature form of CaZr(PO 4 ) 2 was described for the first time Thermal expansion of CaZr(PO 4 ) 2 was studied on the basis of the evolution of the crystal parameters evolution during heating M

Preparation and crystal structure of K2Ce(PO4)2: a new complex phosphate of Ce(iv) having structure with one-dimensional channels

“…high thermal and chemical stability, high radiation resistance and insignificant leachability by water. [1][2][3][4][5][6][7][8] Rich crystal chemistry of phosphates with the variation of nature and ionic radius of cations have been explored in several reports. [6][7][8] In particular such phosphates with tetravalent ions form densely packed structure and they are amenable for immobilization of various actinides, like uranium, neptunium and plutonium.…”

Crystal chemistry of MIIM′IV(PO4)2 double monophosphates

“…Bregiroux [58]. On the opposite, lanthanide monophosphates with the monazite structure, show almost isotropic thermal expansion in the range of 9-10 Â 10 -6 K -1 [83].…”

“…Recently, Bregiroux et al revised the crystal structure and found that CaZr(PO 4 ) 2 actually crystallizes in the orthorhombic space group Pna2 1 (Z¼4) [58]. The coordination number of both cations is seven.…”

A Review of Mechanoluminescence in Inorganic Solids: Compounds, Mechanisms, Models and Applications

“…Spinels, which show ML under low velocity impact, are found to have cationic disorders by co-existence of inverse spinels. A peculiar connectivity of polyhedra of anion framework renders CaZr(PO${}_4$)${}_2$ fairly anisotropic in thermal expansion [193]. The occurrence of multiple traps with different depth in CaZr(PO${}_4$)${}_2$: Eu${}^{2+}$ is likely to provide more channels to release trapped electrons under strains in the process of ML.…”