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Materials Data on CaZr(PO4)2 by Materials Project

CaZr(PO4)2 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional. Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.28–2.85 Å. Zr4+ is bonded to seven O2- atoms to form ZrO7 pentagonal bipyramids that share corners with five PO4 tetrahedra and an edgeedge with one PO4 tetrahedra. There are a spread of Zr–O bond distances ranging from 2.07–2.28 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent ZrO7 pentagonal bipyramids and an edgeedge with one ZrO7 pentagonal bipyramid. There are a spread of P–O bond distances ranging from 1.52–1.56 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three equivalent ZrO7 pentagonal bipyramids. There is one shorter (1.54 Å) and three longer (1.56 Å) P–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one Ca2+, one Zr4+, and one P5+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one Ca2+, one Zr4+, and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Zr4+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to one Ca2+, one Zr4+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a linear geometry to one Zr4+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to one Ca2+, one Zr4+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+, one Zr4+, and one P5+ atom. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ca2+ and one P5+ atom.

36 MATERIALS SCIENCE↗

Crystal structure solution and high-temperature thermal expansion in NaZr 2 (PO 4 ) 3 -type materials

The NaZr 2 P 3 O 12 family of materials have shown low and tailorable thermal expansion properties. In this study, SrZr 4 P 6 O 24 (SrO·4ZrO 2 ·3P 2 O 5 ), CaZr 4 P 6 O 24 (CaO·4ZrO 2 ·3P 2 O 5 ), MgZr 4 P 6 O 24 (MgO·4ZrO 2 ·3P 2 O 5 ), NaTi 2 P 3 O 12 [½(Na 2 O·4TiO 2 ·3P 2 O 5 )], NaZr 2 P 3 O 12 [½(Na 2 O·4ZrO 2 ·3P 2 O 5 )], and related solid solutions were synthesized using the organic–inorganic steric entrapment method. The samples were characterized by in-situ high-temperature X-ray diffraction from 25 to 1500°C at the Advanced Photon Source and National Synchrotron Light Source II. The average linear thermal expansion of SrZr 4 P 6 O 24 and CaZr 4 P 6 O 24 was between −1 × 10 −6 per °C and 6 × 10 −6 per °C from 25 to 1500°C. The crystal structures of the high-temperature polymorphs of CaZr 4 P 6 O 24 and SrZr 4 P 6 O 24 with R 3 c symmetry were solved by Fourier difference mapping and Rietveld refinement. This polymorph is present above ∼1250°C. This work measured thermal expansion coefficients to 1500°C for all samples and investigated the differences in thermal expansion mechanisms between polymorphs and between compositions.

36 MATERIALS SCIENCE↗