Studies on kinetics and mechanism of thermal decomposition of yttrium tartrate trihydrate crystals

Thermogravimetric and differential thermal studies have been used for kinetics and mechanism of thermal decomposition of gel grown crystals of yttrium tartrate trihydrate. Studies have been carried under non-isothermal conditions ranging from 25 to 1000 degrees C. The material is stable up to 218 degrees C and becomes anhydrous at 275 degrees C. The decomposition process occurs in four stages until a complex of yttrium oxide-carbonate is formed at 700 degrees C. The energies of the reactions involved and the mechanism of decomposition at each stage have been examined. The values of kinetic parameters, viz., order of reaction, activation energy and the frequency factor have been evaluated by using the relations Horowitz-Metzger, Coats-Redfern and Piloyan-Novikova. The proposed model for thermal decomposition of the material for all the stages of decomposition is random nucleation model and the order of reaction is one. The final product, that is, yttrium oxide-carbonate has been confirmed by energy dispersive X-ray (EDAX) studies carried on the sample-heated up to 1000 degrees C for thermal analysis. (C) 2007 Elsevier B.V. All rights reserved.