High pressure bulk synthesis of InN by solid state reaction of binary oxide in a multi-anvil apparatus

We present a new method to synthesize bulk indium nitride by means of a simple solid-state chemical reaction carried out under hydrostatic high pressure/high temperature conditions in a multi-anvil apparatus, not involving gases or solvents during the process. The reaction occurs between the binary oxide $In_2O_3$ and the highly reactive $Li_3N$ as nitrogen source, in powder form. The formation of the hexagonal phase of InN, occurring at 350 {\deg}C and P $\geq$ 3 GPa, was successfully confirmed by powder X-ray diffraction, with the presence of $Li_2O$ as unique byproduct. A simple washing process in weak acidic solution followed by centrifugation, allowed to obtain pure InN polycrystalline powders as precipitate. With an analogous procedure it was possible to obtain pure bulk GaN, from $Ga_2O_3$ and $Li_3N$ at T $\geq$ 600{\deg}C and P $\geq$ 2.5 GPa. These results point out, particularly for InN, a clean, and innovative way to produce significant quantities of one of the most promising nitrides in the field of electronics and energy technologies.