Thermal decomposition of gadolinium-doped silver carbonate

Abstract

A thermogravimetric analysis (TGA) study of the decomposition kinetics of gadolinium-doped silver carbonate is reported. The TGA data were used to obtain the activation energy, pre-exponential factor, and order of reaction by the method of Ozawa. Powdered samples were found to obey a first-order rate law from 10 to 90% decomposition. Neither an induction nor an acceleratory period was observed. By decomposing pressed pellets the interface mechanism for the decomposition of Gd-doped silver carbonate was confirmed. Water vapor catalyzed the decomposition, and water incorporated in the crystal lattice during sample preparation may partly account for the high reactivity of Gd-doped silver carbonate. Values for the pre-exponential factor and the activation energy with and without water vapor revealed an apparent compensation effect. The activation energy, 21.4 kcal/mole, for decomposition of Gd-doped silver carbonate in the presence of water vapor agreed favorably with the heat of reaction, suggesting that the recombination of doped silver oxide and carbon dioxide requires little or no energy of activation. The model proposed by Barnes and Stone to describe the decomposition of active silver carbonate is related to the findings with Gd-doped silver carbonate.