Potassium Disorder in the Defect Pyrochlore KSbTeO6: A Neutron Diffraction Study

JOSE ANTONIO ALONSO; XABIER TURRILLAS; HORACIO FALCÓN; SERGIO FEDERICO MAYER; MARÍA TERESA FERNÁNDEZ-DÍAZ

Crystals

Multidisciplinary Digital Publishing Institute

Lugar: 4052 Basel; Año: 2017 vol. 7 p. 24 - 31

2073-4352

KSbTeO6 defect pyrochlore has been prepared from K2C2O4, Sb2O3, and 15% excess TeO2 by solid-state reaction at 850 ◦C. Direct methods implemented in the software EXPO2013 allowed establishing the basic structural framework. This was followed by a combined Rietveld refinement from X-ray powder diffraction (XRD) and neutron powder diffraction (NPD) data, which unveiled additional structural features. KSbTeO6 is cubic, a = 10.1226(7) Å, space group Fd3m, Z = 8 and it is made of a mainly covalent framework of corner-sharing (Sb,Te)O6 octahedra, with weakly bonded K+ ions located within large cages. The large K-O distances, 3.05(3)?3.07(3) Å, and quite large anisotropic atomic displacement parameters account for the easiness of K+ exchange for other cations of technological importance.