Interpretation of L-Ta2O5-type diffraction patterns in terms of a one-dimensional shift lattice

Abstract

Electron-diffraction patterns from phases with the L-Ta₂O₅ structure from the L-Ta₂O₅–TiO₂, L-Ta₂O₅–Al₂O₃, L-Ta₂O₅–WO₃, L-Ta₂O₅–ZrO₂ and L-Ta₂O₅–HfO₂ systems have been interpreted in terms of a shift lattice. The interpretation was confirmed by both computer and optical simulations of diffraction patterns. In these systems all the shift-lattice parameters were constant except for β/α, which varied smoothly over the composition ranges studied, from ca. 4.6 for the most oxygen-rich compositions found in the WO₃–Ta₂O₅ system to 16 or more in the most oxygen-poor samples found in the HfO₂–Ta₂O₅ system. The oxygen content of the phases is controlled by the relative amounts of matrix and shift-lattice regions in the samples. The compositions of these two components were estimated as MO_2.62 and MO_2.43, respectively.