Ammonothermal Nitride Synthesis

Ammonothermal Nitride Synthesis

Author: Robert Hughes

Ternary nitrides are important materials with many applications. Materials such as CaAlSiN3:Eu2+ (CASN) are used industrially as red-light emitters for phosphor-converted light-emitting diodes (pc-LEDs). Li3AlN2 can be used as a lithium solid electrolyte.

Wolfgang Schnick, University of Munich (LMU), Germany, and colleagues have developed high-pressure autoclaves to allow materials synthesis using supercritical ammonia as both solvent and nitrogen source. The vessels, made from a nickel-based superalloy, allow reactions to take place at high temperature and pressure (up to a maximum of 170 MPa at 1100 K). The ammonothermal synthesis of nitrides has been known since the 1960s, however, the ability to reach higher temperatures and pressures allows access to novel phases.

Using the new vessels, the team has synthesized CaGaSiN3:Eu2+, the gallium analogue of the CASN phosphor material. This is the first example of a gallium-containing nitridosilicate. Similarly to CASN, it is a red-emitting phosphor. Other novel nitrides with useful properties could be synthesized in the improved reaction vessel.


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