Formation and characterization of samarium oxide generated from different precursors

Abstract

Sm(NO 3) 3·6H 2O and Sm 2(C 2O 4) 3·10H 2O were used as precursors for the formation of Sm 2O 3. Thermal processes involved in the decomposition course of both salts up to 800 °C in air were monitored by nonisothermal gravimetry and differential thermal analysis. Intermediates and final solid products were characterized by IR-spectroscopy, X-ray diffraction and scanning electron microscopy. The results showed that Sm(NO 3) 3·6H 2O decomposes completely through nine endothermic mass loss processes. The dehydration occurs through the first four steps at 90, 125, 195, and 240 °C, culminating in a crystalline nitrate monohydrate, which subsequently decomposes to Sm(OH)(NO 3) 2 at 355 °C. The latter decomposes rapidly to form a stable and crystalline SmO(NO 3) at 460 °C, through nonstoichoimetric unstable intermediates. Finally Sm 2O 3 forms at 520 °C. For the oxalate, the dehydration occurs in five steps: the anhydrous oxalate is thermally unstable and immediately decomposes to Sm 2O 3 at 645 °C through two unstable intermediates. The crystalline oxide obtained from the nitrate contains larger pores than the oxide obtained from the oxalate, as indicated from scanning electron microscopy (SEM) results.