X-ray diffraction study on formation of ErNbO<F>4</F> powder

The formation of ErNbO<F>4</F> powder, prepared by calcining an Er<F>2</F>O<F>3</F> (50 mol%) and Nb<F>2</F>O<F>5</F> (50 mol%) powder mixture at 1100 and 1600 <F>°</F>C for different durations, was investigated by using X-ray diffraction. The experimental results have displayed that although the solid-state reaction had started to some extent when the mixture was pre-calcined at 1100 <F>°</F>C for a duration of 13 h, the two original phases Er<F>2</F>O<F>3</F> and Nb<F>2</F>O<F>5</F> still dominated the mixture. When the duration of the calcination reaction was increased to 120 h at the same temperature, the resultant mixture experienced a nearly complete phase transformation. Accordingly, the ErNbO<F>4</F> phase was dominant phase in the mixture. Nevertheless, a small portion of the raw powder still existed in the mixture. When the calcining temperature was elevated to 1600 <F>°</F>C, ErNbO<F>4</F> powder with higher purity could be obtained for a relatively much shorter duration (only up to several tens of hours). A simple formation mechanism of ErNbO<F>4</F>, an elevated-temperature-assisted solid-state chemical reaction: <F>Er2O3+Nb2O5⇌2ErNbO4</F>, is suggested. In addition, the present experimental results offer important evidence for the formation of the additional phase ErNbO<F>4</F> induced in Er:LiNbO<F>3</F> crystals by vapour transport equilibration (VTE) treatment. [Copyright &y& Elsevier]