The variable properties of solid solutions A 1-x B x XO 4 : Tunable photoluminescence in the case of Sr 1-x Pb x WO 4 series
Résumé
Over the ten past years, various experimental studies of solid solutions A 1-x B x XO 4 (e.g. A = Sr, B = Pb, X = W) with scheelite structures have evidenced correlations between structural, vibrational modifications due to chemical substitution, and increasing photoluminescence intensities under UV or X-ray excitation. We propose a simple semi-empirical approach based on local zones with different compositions, allowing simulating the variations of structural, vibrational and photoluminescence characteristics, in the full composition range 0≤x≤1. The structural characteristics are cell parameters, cell distortions or crystallite size effect, Debye-Waller factors, Raman shifts characterizing vibrations and photoluminescence signals under UV or X-ray excitations. Each property is assumed to be represented by a non-linear function Y(x) depending on composition x and on local microstructural disorder. To illustrate this approach based on the coexistence of local zones with different compositions, we have fitted the Y(x) function to experimental data, which allowed us determining the significant parameters characteristic of the series with A=Sr, B=Pb and X = W. These parameters deliver a new microstructural interpretation of the increasing photoluminescence intensities observed for intermediate composition x in solid solutions. A generalization of this approach to other series of solid solutions is quite possible.
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