Syntheses and Structural Characterizations of New Inorganic Anhydrous Borate Compounds

Abstract

<p> A number of new ternary borate compounds have been synthesized, and their crystal structures have been characterized via X-ray and neutron diffraction techniques. A series of new compounds with the composition PbMBO4 (M = Cr, Mn, Fe, Ga) has been prepared from solid-state reactions and from single crystal growths using PbO as a flux. They crystallize in the orthorhombic Pnma space group and represent a new structure-type for the family of anhydrous borates. The PbAlBO4 compound undergoes a phase transformation at high temperatures, which has been investigated by in-situ powder neutron diffraction experiments. The structure of β-PbAlBO4 has been solved from powder X-ray diffraction data and subsequently confirmed by a Rietveld refinement of powder neutron diffraction data. The investigation of the SrO - Ga2O3 - B2O3 system has led to the synthesis of a new structure-type, SrGaBO4, from solid-state reactions. Its crystal structure has been determined from powder X-ray diffraction data. It crystallizes in the orthorhombic Pbam space group, and is structurally related to the previously known alumino-borate compounds, SrAlBO4 and CaAlBO4. The "Ba2Ti2B2O9" compound has been re-formulated as Ba3Ti3B2O13, and its crystal structure has been determined by single crystal X-ray diffraction. This compound crystallizes in the non-centrosymmetric P6 2m space group. It is isostructural with K3Ta3B2O12 and the high temperature phase of K3Nb3B2O12.</p>