Abstract Gd 2(C 2O 4) 3·10H 2O was used as a parent compound for the formation of Gd 2O 3 at up to 800 °C in an atmosphere of air. Thermal processes occurring during the decomposition course were monitored by means of differential thermal analysis, DTA, and Thermogravimetry, TG. Intermediates and final solid products were characterized by XRD and IR Spectroscopy. The results showed that Gd 2(C 2O 4) 3.10H 2O decomposes to Gd 2O 3 at 575 °C through different intermediates, Gd 2O 2CO 3 was defined as a stable intermediate. The final product Gd 2O 3 has a surface area of 23.4 m 2 g −1.