Thermogravimetry study of Gd2O3 chlorination: Kinetics and characterization of gadolinium oxychloride

Abstract

The reaction between Gd2O3(s) and Cl2(g) was studied in a high-resolution thermogravimetric system. The reaction product was GdOCl, which was the unique solid phase produced in all the temperature range studied. The GdOCl is subsequently chlorinated producing GdCl3 for temperatures above 1123 K. The system is under chemical control for temperatures below 723 K. It was found that the reaction order with respect to the chorine partial pressure is 0.77 and the activation energy is 132 kJ mol-1 for the temperature range of 623-723 K. The global rate equation was developed. The GdOCl obtained was characterized by X-ray diffraction, scanning electron microscopy and magnetic measurements. The structure of GdOCl was refined with the Rietveld method, and it crystallized in a tetragonal form of REOX possessing the Matlockite-type (PbFCl) structure. The magnetic measurements indicated that the sample is paramagnetic at all the measurement ranges. The parameters of the Curie-Weiss law obtained were as follows: θ = -12.0 K, C = 7.9592 emu K mol-1 and μ eff = 7.98μ B.