A study of the chemical reactions involved in Li–Ca–N system

The chemical reactions and phases involved in the potential flux system of Li–Ca–N for the growth of bulk GaN crystals have been investigated under varying conditions. It is found that no preferential nitrification of Li or Ca by N2 in Li–Ca melts at 500 °C. Only the ternary compound LiCaN is identified in the Li–Ca–N system under the present experimental conditions. Static N2 pressures are found to enhance the formation of LiCaN compared to an N2 stream. LiCaN forms from two possible pathways: one is a modified metathesis chemical reaction represented by Li3N+Ca→LiCaN+2Li, and the other is a combination chemical reaction represented by Li3N+Ca3N2→3LiCaN. The formation of LiCaN by the metathesis reaction is thermodynamically favored over the other pathway. In addition, the formation of LiCaN might benefit from a slightly larger initial amount of Li3N compared with Ca or Ca3N2.