The Synthesis of Crystalline Gallium Nitride Using Solid-State Metathesis Reactions at High Pressures

Solid-state metathesis (exchange) reactions provide a rapid method to produce high quality refractory materials under ambient conditions. An investigation into solid-state metathesis reactions under pressure using Bridgman anvils and a girdle-type apparatus has led to the bulk synthesis of GaN, TaN and CrN, which are inaccessible under ambient pressure/ temperature conditions. For example, high quality, crystalline gallium nitride can be rapidly (< 1 sec) synthesized from the reaction of gallium (III) iodide and lithium nitride confined at a pressure of 4.5 GPa and initiated. Characterization of these compounds includes powder X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, energy dispersive spectroscopy and scanning electron microscopy. The single-phase gallium nitride made by metathesis reactions under pressure displays significant photoluminescence intensity in the blue/ultraviolet region.