Time-resolved study by X-ray powder diffraction with position-sensitive detector: rate of the β-Cs2Cdl4 transformation and the effect of preferred orientation

Abstract

A time-resolved X-ray powder diffraction of the transformation, at room temperature, of the metastable β-Cs2Cdl4 phase into α-Cs2Cdl4 is described. It is based on data collected by means of a conventional X-ray diffraction system combined to a curved position-sensitive detector. The transformation is governed by a nucleation and a three-dimensional growth process, and its rate depends on the particle size and crystal imperfections. When particle sizes are less than 40 μm, the rate of the transformation strongly decreases in the later stage of growth, due to the stresses produced by structural modifications. Particular attention is paid to the fact that the quantitative interpretation of experimental data in kinetic terms, can be influenced by the existence of a preferred orientation effect of the crystallites in the sample.