Oxygen Interaction with Hexagonal OsB₂ at High Temperature

The stability of ReB₂-type hexagonal OsB₂ powder at high temperature with oxygen presence has been studied by thermogravimetric analysis, differential scanning calorimetry, SEM, EDS, and high-temperature scanning transmission electron microscopy and XRD. Results of the study revealed that OsB₂ ceramics interact readily with oxygen present in reducing atmosphere, especially at high temperature and produces boric acid, which decomposes on the surface of the powder resulting in the formation of boron vacancies in the hexagonal OsB₂ lattice as well as changes in the stoichiometry of the compound. It was also found that under low oxygen partial pressure, sintering of OsB₂ powders occurred at a relatively low temperature (900°C). Hexagonal OsB₂ ceramic is prone to oxidation and it is very sensitive to oxygen partial pressures, especially at high temperatures.