High-pressure synthesis and crystal structure analysis of PbTeO₄, a UV transparent material

Using the additional parameter pressure (Walker-type multianvil device), the lead(II) oxidotellurate(VI) PbTeO₄ was synthesized at conditions of 8 GPa and 750 °C, and for the first time its crystal structure was determined using single-crystal X-ray diffraction data. PbTeO₄ crystallizes with four formula units in the monoclinic space group I2/a with unit cell parameters a = 5.4142(4), b = 4.9471(4), c = 12.0437(11) Å, β = 99.603(3)°, and V = 318.07(5) ų. UV-Vis measurements revealed UV transparency down to 200 nm. From the diffuse reflectance data experimental band gaps (E_g(direct) = 2.9 eV/E_g(indirect) = 2.8 eV) were determined and compared with calculated values. Temperature-dependent X-ray powder diffraction and complementary thermal analysis measurements revealed a stability range of PbTeO₄ up to 625 °C. Additionally, theoretical calculations at DFT level of theory were carried out to obtain the electronic band structure, X-ray powder diffraction patterns, IR/Raman vibrational spectra and Mulliken partial charges. The electron localization function (ELF) was visualized to emphasize the presence of the electron lone pair E in the coordination sphere of the Pb^II atom.