Reversible Structural Transformation between Polar Polymorphs of Li2GeTeO6

• DOI: 10.1021/acs.inorgchem.8b03114
• Publication Date: 2019-01-04T17:06:44Z
• Authors: Mei-Huan Zhao; Wei Wang; Yifeng Han; Xueli Xu; Zhigao Sheng; Yaojin Wang; Meixia Wu; Christoph P. Grams; Joachim Hemberger; David Walker; Martha Greenblatt; Man-Rong Li
• Keywords: Corundum; Orthorhombic crystal system; Ilmenite; Ambient pressure

Li2GeTeO6 prepared at ambient pressure adopts the corundum derivative ordered ilmenite structure (rhombohedral R3). When heated 1073 K and 3–5 GPa, as-made can convert into a LiSbO3-derived Li2TiTeO6-type phase (orthorhombic Pnn2), which is third double A2BB′O6 in addition to Li2TiTeO6 Li2SnTeO6. This Pnn2 spontaneously reverts R3 if annealed up 1023 pressure. Although crystal structural analyses second harmonic generation measurements clearly demonstrate polar nature of both phases, P(E) dielectric do not show any convincing ferroelectric response. Given large estimated spontaneous polarization (17 80 μC/cm2), absence behavior could be attributed random domain distribution leakage due Li-ion migration.