Single-Crystal Structure of HP-Sc2TeO6 Prepared by High-Pressure/High-Temperature Synthesis

Abstract

The first high-pressure scandium tellurate HP-Sc2TeO6 was synthesized from an NP-Sc2TeO6 normal-pressure precursor at 12 GPa and 1173 K using a multianvil apparatus (1000 t press, Walker-type module). The compound crystallizes in the monoclinic space group P2/c (no. 13) with a = 729.43(3), b = 512.52(2), c = 1095.02(4) pm and β = 103.88(1)°. The structure was refined from X-ray single-crystal diffractometer data: R1 = 0.0261, wR2 = 0.0344, 568 F2 values and 84 variables. HP-Sc2TeO6 is isostructural to Yb2WO6 and is built up from TeO6 octahedra, typical for tellurate(VI) compounds. During synthesis, a reconstructive transition from P321 (normal-pressure modification) to P2/c (high-pressure modification) takes place and the scandium–oxygen distances as well as the coordination number of scandium increase. However, the coordination sphere around the Te6+ cations gets only slightly distorted. High-temperature powder XRD investigations revealed a back-transformation of HP-Sc2TeO6 to the ambient-pressure modification above 973 K.

First ternary tungsten tellurate(iv) WTe2O7 with unique crystal structure type

“…[8][9][10][11][12][13] In addition to high-pressure phase transformations and the synthesis of polymorphs, new compositions can also be stabilized that would not be accessible at ambient pressure conditions. [14][15][16] Using this technique, we recently reported on the synthesis of HP-Mg 3 TeO 6 , an SHG active and UV-transparent material, 17 HP-Sc 2 TeO 6 , 18 and HP-Co 3 TeO 6 , 19 which shows magnetoelectric behavior. All the aforementioned tellurates are oxotellurates(VI) without exception, because a stabilization of oxotellurates(IV) at HP/HT conditions is challenging.…”