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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 powdersmore » occurred at a relatively low temperature (900°C). Finally, hexagonal OsB₂ ceramic is prone to oxidation and it is very sensitive to oxygen partial pressures, especially at high temperatures.« less

We produced hexagonal ReB₂-type IrB₂ diboride and orthorhombic IrB monoboride phases, that were previously unknown and saw them produced by mechanochemical syntheses. High energy ball milling of elemental Ir and B powder for 30 h, followed by annealing of the powder at 1050 °C for 48 h, resulted in the formation of the desired phases. Both traditional laboratory and high resolution synchrotron X-ray diffraction (XRD) analyses were used for phase identification of the synthesized powder. Additionally, scanning electron microscopy and transmission electron microscopy were employed, along with XRD, to further characterize the microstructure of the phases produced.