K3BaTeB7O15: A new borotellurite with mixed metal cations

Abstract

Tellurium-based borates are known to exhibit good optical properties and structural diversity, which are beneficial for obtaining new multicomponent borate optical materials. Therefore, a new borotellurite K3BaTeB7O15 with an anionic framework interconnected by TeO3 groups and pseudo-layers consisting of B7O16 units, was synthesized. The compound was synthesized by the high-temperature solution method and crystallized in the P21/c (No.14) space group, which has a complex cation. The UV-–vis–NIR diffuse reflectance spectra showed that the absorption edge of K3BaTeB7O15 was approximately at 235 nm, corresponding to a large experimental band gap of 4.2 eV. Thermal property analysis indicated that the compound was stable below 570 °C. The electronic energy band structure and partial density of states were calculated and discussed, and its birefringence was approximately 0.03@1064 nm. The results of ELF prove the existence of the stereochemical activity of the TeO3 group in K3BaTeB7O15.