Shedding light on intrinsic characteristics and optical properties of novel selenite and tellurite crystals ZrSe2O6, HfSe2O6 and HfTe3O8

Abstract

Selenite and tellurite compounds have garnered a lot of attention in both fundamental and applied chemistry. Se⁴⁺ and Te⁴⁺ cations possess lone pair electrons, which change the coordination environments and performance of these compounds. Here, three new transition metal selenite and tellurite compounds, MSe₂O₆ (M = Zr, Hf) and HfTe₃O₈, have been obtained by conventional hydrothermal reactions. The crystallographic structures of the three compounds are discussed in detail; meanwhile, thermal analysis, optical spectra, birefringence and theoretical calculations are also reported. Isostructural ZrSe₂O₆ and HfSe₂O₆ exhibit partially distorted octahedral and tetrahedral configurations. Moreover, ZrSe₂O₆ and HfSe₂O₆ have birefringence (Δn = 0.1052, 0.096) and short UV cut-off edges (212, 208 nm), and compared with ZrSe₂O₆, the thermal stability of HfSe₂O₆ is slightly larger. ZrSe₂O₆ and HfSe₂O₆ are adequate candidates as birefringent crystals in the UV region. Remarkably, HfTe₃O₈ not only has high thermal stability, but also provides a short UV cut-off edge (234 nm). It can meet the multiple requirements of the developing photoelectric system for UV window materials and has broad application prospects. Furthermore, the intrinsic relationship between the physical properties of the three crystals and their unique electronic structures is revealed.