Abstract
La(NO
3)
3·6H
2O was used as a precursor to produce La
2O
3 at 650°C in an atmosphere of air. Thermal processes occurred were monitored by means of thermogravimetry, differential thermal analysis, and gas-mass spectrometry. Infrared (IR)-spectroscopy, X-ray diffractometry and scanning electron microscopy characterized the intermediates and final solid products. The results showed that, La(NO
3)
3·6H
2O decomposes through nine endothermic weight loss processes. Five dehydration steps occurred at 90, 105, 150, 175 and 215°C, leading to the formation of crystalline nitrate monohydrate, which decomposes to La(OH)(NO
3)
2 at 410°C. The latter, decomposes to La
2O
3 at 640°C, via two different intermediates; LaO(NO
3) at 440°C, and non-stoichiometric unstable, La(O)
1.5(NO
3)
0.5 at 570°C. The gaseous decomposition products as identified by gas-mass spectroscopy were water vapor, nitric acid and nitrogen oxides (NO, NO
2 and N
2O
5). The final product La
2O
3 has a large crystalline containing pores, voids and cracks, with a surface area of 23 m
2 g
−1. Also it possessed Lewis acidic and basic sites, as indicated by Pyridine adsorption.