Effect of Lithium Nitride on Chemical Interaction of Hafnium and Tantalum Diborides with Iridium

ABSTRACT The primary products formed by the interaction of hafnium and tantalum diborides with lithium nitride over the temperature range of 800°C–1400°C are solid solution phases based on metal monoborides and hexagonal boron nitride. Density functional theory calculations indicate that nitrogen and oxygen atoms stabilize the crystal lattices of metal monoborides. In the reaction products of equimolar multicomponent HfB 2 –Li 3 N–Ir system, metal monoboride and boron nitride phases coexist with the iridium‐containing compounds Hf 2 Ir 5 B 2 and HfIr 3 B x . In the equimolar TaB 2 –Li 3 N–Ir system, TaB and BN phases coexist with TaIr 3 . X‐ray diffraction analysis does not reveal the formation of iridium borides or boron‐rich ternary compounds, such as HfIr 3 B 4 or TaIr 2 B 2 .