Formation of ZnO₄ Tetrahedra and ZnO₆ Octahedra in TeZnO₃ Synthesized under High Pressure

Abstract

A new TeZnO₃ phase was synthesized by high-pressure techniques. Different from the ambient-pressure orthorhombic phase composed of ZnO₅ units, the current high-pressure one crystallizes to a monoclinic structure with space group P2₁/ n. Moreover, both ZnO₄ tetrahedral and ZnO₆ octahedral polyhedra are found to occur in this new phase, providing a unique Zn-based material system that simultaneously possesses two distinct coordinated units. Because the outermost orbitals are fully occupied for both Zn²⁺ and Te⁴⁺, the compound exhibits diamagnetism and strong insulating behavior with a wide bandgap as large as 6.0 eV. Dielectric constant and specific heat measurements show a broad anomaly around 240 K. Low-temperature synchrotron X-ray diffraction reveals an isostructural phase transition at this temperature.