X-ray powder diffraction of Ag2Te at temperatures up to 1123 K

Abstract

AbstractX-ray powder diffraction was performed onβ-Ag2Te at room temperature, on ion conductingα-Ag2Te at 523 K, 723 K and 923 K respectively and onγ-Ag2Te at 1123 K.Rietveld profile refinement ofβ-Ag2Te confirmed the space groupP21/cand the positional parameters of the model of Frueh (Z. Kristallogr.112(1959) 44–52).For theα-modification in space groupFm[unk]m, best results were obtained for a model with a statistical distribution of Ag ions: about 60% of the available Ag ions were placed into 32f(xxx) positions around the tetrahedral 8c(¼ ¼ ¼) sites and the remainder on the 48i(xx½) positions. The probability density function (PDF) calculated with these formal structure parameters suggests next neighbour jumps of Ag ions via the 48isites.The first structure refinement ofγ-Ag2Te showed it to crystalize in space groupIm[unk]mand to be iso-structural toα-AgI. Third order anharmonic coefficients of the temperature factor of the Ag ions could be refined from our X-ray powder data. Corresponding PDF maps show Ag-densities bridging next nearest as well as second next nearest neighbours.