Structural insights for the design of new borate–phosphates: synthesis, crystal structure and optical properties of Pb4O(BO3)(PO4) and Bi4O3(BO3)(PO4)

Abstract

Two new metal borate–phosphates, Pb₄O(BO₃)(PO₄) (1) and Bi₄O₃(BO₃)(PO₄) (2), have been successfully designed and synthesized. The structures of the title compounds were determined by single-crystal X-ray diffraction. The title compounds have similar crystal structures consisting of oxygen-centered (OPb₄) or (OBi₄) tetrahedra as well as isolated BO₃ and PO₄ groups. Structural comparison and the Madelung energy calculation indicate that the title compounds also exhibit a strong correlation with the known metal borates and phosphates. In addition, a strategy of BO₃–PO₄ substitution is proposed for designing new borate–phosphates. Thermal analyses, IR spectroscopy and UV-vis-NIR diffuse reflectance spectroscopy have also been performed.