Bulk Synthesis and Transport Properties of Rocksalt-Type Ti1–xMgxN Solid Solution

Abstract

Owing to the decomposition issue of Mg3N2, many Mg-containing ternary nitrides were prepared by the hybrid arc evaporation/sputtering technique, which has the advantages including access to the unstable phases, high film purity, good density, and uniform film formation but the drawbacks of cost and long production cycle for the required targets. In the present study, we demonstrate that rocksalt-type Ti1-xMgxN, previously prepared exclusively by the thin-film methods, can be obtained as a disordered cubic phase by the conventional bulk synthesis method through a facile one-step reaction. Employing a combination of experimental measurements and theoretical calculations, we discover that the crystal structure and the physical properties of the as-synthesized Ti1-xMgxN solid solution can be tuned by the Mg content; a metal-to-semiconductor transition and also suppression of the superconducting phase transition are observed when the Mg and Ti content ratio increases to close to 1. Theoretical calculations indicate that the lattice distortions in the disordered Ti1-xMgxN induced by the different ionic sizes of Mg and Ti increase with the Mg content and the disordered cubic rocksalt structures become unstable. The ordered rocksalt-derived structures are more stable than the disordered rocksalt structures on composition x = 0.5. Furthermore, electronic structure calculations provide an insight into the low resistance behavior and transport property evolution of Ti1-xMgxN from the aspects of Ti3+ content, the cation distribution, or nitrogen defects. The results highlight the feasibility of the simple bulk route for the successful synthesis of Mg-containing ternary nitrides and the heterovalent ion substitution on modulating the properties of nitrides.