Thermal dehydration kinetics involved during the conversion of gadolinium hydroxide to gadolinium oxide

Non-isothermal dehydration kinetics of gadolinium hydroxide (Gd(OH)₃) was studied by thermogravimetry analysis (TGA), and differential thermal analysis (DTA). It was observed that the dehydration of Gd(OH)₃ occurred in two steps. In step I, Gd(OH)₃ dehydrates to GdOOH at ∼ 596 K. Finally, Gd₂O₃ is formed after complete dehydration of GdOOH at ∼710 K. The kinetic triplets (activation energy, pre-exponential factor and reaction mechanism) were calculated for step I and step II. The activation energy was determined by using the Kissinger–Akahira–Sunsose (KAS) iso-conversional method. The results indicated that the average activation energy was higher for step II (91.29 kJ/mol) as compared to step I (77.94 kJ/mol). The reaction mechanism was estimated by following two different master plot methods such as Criado and integral master plot method. Both the master plot methods have shown similar results. It was found that the Avrami–Erofeev A3 nucleation reaction mechanism dominated in both the dehydration steps.