Synthesis and Structure Determination of the High Temperature Form of La2WO6

This article presents the synthesis, structure determination, and structure analysis of α-La2WO6. This high temperature polymorph was directly observed using laboratory in situ high-temperature X-ray powder diffraction and isolated at room temperature by rapid quenching from 1600 °C. Ab initio structure determination has been performed at room temperature by combining electron diffraction results with an analysis of synchrotron and neutron powder diffraction data by charge-flipping algorithm methods. The α-La2WO6 phase is found to crystallize in the Pm21n (No. 31) orthorhombic space group (Z = 6) with cell parameters: a = 16.5513(1) Å, b = 5.52003(3) Å, c = 8.88326(3) Å and a measured density of 6.82(1) g·cm–3 at room temperature. This previously uncharacterized high temperature α-La2WO6 form (>1450 °C) may be described as a regular paving between six [WO6] octahedra alternating with 12 isolated lanthanum atoms. The conductivity properties have been measured and compared to the low temperature (β) polymorph.