Recent advances in new hard high-pressure nitrides

Since the discovery of spinel nitrides in 1999, there has been a lot of effort in basic science to further develop advanced nitrides and electronic nitrides. The aim and scope of the research in this field is to synthesize novel nitrides for structural and functional applications. Silicon-based spinel nitrides combine ultrahigh hardness with high thermal stability against decomposition in different environments, suggesting potential applications as cutting tools. These materials are also expected to show interesting optoelectronic properties, which may lead to applications in light-emitting diodes. The synthesis of spinel silicon and germanium nitrides at ultrahigh pressures and temperatures, as well as the successful synthesis of tin nitride at ambient pressure, has created an enormous impact on both the basic science and technological development of advanced nitrides. Moreover, the discovery of novel phases of transition metal nitrides, such as Zr3N4 and Hf3N4 with a Th3P4 structure, as well as the recently reported nitrides of Pt and Mo, demonstrates the scientific potential of highpressure synthesis techniques in the field of materials science. Here, the state of the art in the field of novel hard materials based on nitrides synthesized reproducibly under high pressure is reviewed.