Editing Samarium (section)

===Oxides===
The most stable oxide of samarium is the [[sesquioxide]] Sm<sub>2</sub>O<sub>3</sub>. Like many samarium compounds, it exists in several crystalline phases. The trigonal form is obtained by slow cooling from the melt. The melting point of Sm<sub>2</sub>O<sub>3</sub> is high (2345&nbsp;°C), so it is usually melted not by direct heating, but with [[induction heating]], through a radio-frequency coil. Sm<sub>2</sub>O<sub>3</sub> crystals of monoclinic symmetry can be grown by the flame fusion method ([[Verneuil process]]) from Sm<sub>2</sub>O<sub>3</sub> powder, that yields cylindrical boules up to several centimeters long and about one centimeter in diameter. The boules are transparent when pure and defect-free and are orange otherwise. Heating the metastable trigonal Sm<sub>2</sub>O<sub>3</sub> to {{convert|1900|C|F}} converts it to the more stable monoclinic phase.<ref name="smo" /> Cubic Sm<sub>2</sub>O<sub>3</sub> has also been described.<ref name="smo2" />

Samarium is one of the few lanthanides that form a monoxide, SmO. This lustrous golden-yellow compound was obtained by reducing Sm<sub>2</sub>O<sub>3</sub> with samarium metal at high temperature (1000&nbsp;°C) and a pressure above 50&nbsp;kbar; lowering the pressure resulted in incomplete reaction. SmO has cubic rock-salt lattice structure.<ref name="smox" /><ref name="g1239">[[#Greenwood|Greenwood]], p. 1239</ref>