Application of Fission Chamber to Uranium Microanalysis

Abstract

In the framework of general studies of structural phase transitions in disordered materials, the crystal structure of mixed perovskites Rb 1−x K x CaF 3 has been investigated by high resolution powder diffraction using synchrotron radiation, for three selected impurity concentrations x = 0.05, 0.20, 0.32. The symmetries and space groups have been fully determined according to Glazer's formalism and the structures refined using the Rietveld method. Special attention was paid to pre-transitional effects and phase coexistence. Thanks to this thorough examination, a full phase diagram, transition temperature versus concentration, is suggested and interpreted from a model using the replica trick method and the mean field approximation. The validity of this model is discussed. §