Thermal effect on BaFCl: High-temperature X-ray diffraction

Results of the Rietveld analysis of high-temperature powder XRD data of BaFCl are reported and discussed for the first time. The values of a and c increase monotonically with T while those of cia and density decrease. Linear thermal expansion coefficients pass through a minimum at ca. 350 degrees C. The cell parameters depend on the sample preparation conditions. The interplanar separation distance between Ba and F planes decreases while that between Ba and Cl-1 planes, and between Cl-1 and Cl-2 planes, increases with temperature. The bond length, connecting any ion with Ba, and that between Cl-1 and Cl-2 increases with T. The sintering of the sample powder is manifested in many of the Rietveld parameters. The efficiency of the Rietveld analysis of powder XRD data in obtaining the cell parameters, fractional coordinates, sample compaction, preferred orientation, etc. has been amply demonstrated. (C) 1997 Elsevier Science B.V.