Thermolysis mechanism of samarium nitrate hexahydrate |
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Authors: | P Melnikov I V Arkhangelsky V A Nascimento A F Silva L Z Zanoni Consolo |
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Institution: | 1. School of Medicine/UFMS, Campo Grande, MS, Caixa Postal 549, Brazil 2. School of Chemistry, Moscow State University, Vorobievy Gory, 119517, Moscow, Russia
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Abstract: | Thermal decomposition of samarium nitrate hexahydrate Sm(NO3)3·6H2O has been investigated by thermogravimetry, differential scanning calorimetry, infrared spectroscopy, and X-ray diffractometry. This is a complex process that involves slow dehydration and fast concomitant internal hydrolysis. It is markedly different from the processes described for other members of the lanthanide series. At the first stage, pyrolysis is accompanied by removal of water and nitric acid to form samarium pentahydrate Sm(NO3)3·5H2O and intermediate oxonitrates containing O–Sm–OH groups. No traces of SmONO3 were detected. It is assumed that the existence of intermediate structures with six atoms of samarium best fits the experimental results. At higher temperatures, these products undergo further degradation, lose nitrogen dioxide, water, and oxygen, and finally, after having lost lattice water, are transformed into a cubic form of samarium oxide. |
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