Raman scattering study on formation of ErNbO₄ powder

A Raman scattering study was performed on ErNbO₄ powder prepared by thermally calcining the mixture of 50 mol% Er₂O₃ and 50 mol% Nb₂O₃ powder at 1100°C and 1600°C over different durations. The scattering features are summarized and discussed. In combination with X-ray diffraction results some useful information on the preparation of the ErNbO₄ powder was obtained. A simple formation mechanism for ErNbO₄ powder phase was suggested on the basis of an elevated-temperature-assisted solid-state chemical reaction: Er ₂O₃ + Nb₂O₅ ⇔ 2ErNbO ₄. A Raman study was also performed on some samples powdered from vapor-transport-equilibrated (VTE) Er(2.0 mol%):LiNbO₃ crystals, in which nanocrystalline ErNbO₄ was induced by the VTE procedure. A comparison of the spectra of the crystal-powdered samples with those of directly calcined powder revealed that Raman peaks observed in the calcined powder cannot be resolved in either the single crystal or the crystal-powdered sample due to the lower content of the ErNbO₄ phase in the crystal. Present Raman results on powdered crystal support our earlier work on the assignment of the phonon modes in LiNbO₃ crystals.