Copper scandium zirconium phosphate: occupancy of the M1 and M2 sites in the temperature range 100–300 K
International Union of Crystallography, 2013
Acta Crystallographica Section C
Volume 69, Issue 2, pages 105–110, February 2013
How to Cite
Bond, A. D. and Warner, T. E. (2013), Copper scandium zirconium phosphate: occupancy of the M1 and M2 sites in the temperature range 100–300 K. Acta Crystallographica C, 69: 105–110. doi: 10.1107/S0108270113000553
The title compound, with nominal formula Cu2ScZr(PO4)3, has a beige coloration and displays fast Cu+ cation conduction at elevated temperatures. It adopts a NASICON-type structure in the space group Rc. The examined crystal was an obverse–reverse twin with approximately equal twin components. The [ScIIIZrIV(PO4)3]2− framework is composed of corner-sharing Sc/ZrO6 octahedra and PO4 tetrahedra. The Sc and Zr atoms are disordered on one atomic site on a crystallographic threefold axis. The P atom of the phosphate group lies on a crystallographic twofold axis. Nonframework Cu+ cations occupy three positions. Two of the Cu+ positions generate an approximately circular distribution around a site of symmetry, referred to as the M1 site in the NASICON-type structure. The other Cu+ position is situated close to the twofold symmetric M2 site, displaced into a position with a distorted square-based pyramidal coordination geometry. The structure has been determined at 100, 200 and 300 K. Changes in the refined site-occupancy factors of the Cu+ positions suggest increased mobility of Cu+ around the circular orbit close to the M1 site at room temperature, but no movement into or out of the M2 site. Free refinement of the Cu site-occupancy factors suggests that the formula of the crystal is Cu1.92(1)ScZr(PO4)3, which is consistent with the low-level presence of Cu2+ exclusively in the M2 site.