Synthesis of U3Se5 and U3Te5 type polymorphs of Ta3N5 by combining high pressure–temperature pathways with a chemical precursor approach

Abstract

Combining metastable precursors with high pressure–temperature treatment is a powerful tool to make nitrogen-rich metal nitrides. Two new dense polymorphs of Ta₃N₅ have previously been theoretically predicted, with U₃Se₅ (Pnma) and U₃Te₅ (Pnma) structure types, and are now shown to exist. Amorphous Ta₃N₅ from thermal ammonolysis of an amorphous polymeric precursor was laser heated at 22 GPa and examined using synchrotron X-ray diffraction to reveal the emergence of these two novel polymorphs.