Novel nanoceramics from in situ made nanocrystalline powders of pure nitrides and their composites in the system aluminum nitride AlN/gallium nitride GaN/aluminum gallium nitride Al0.5Ga0.5N

Presented are investigations of in situ preparation of composite nanopowders of AlN, GaN, and, optionally, solid solution Al0.5Ga0.5N, which were used in no-additive, high-pressure/high-temperature sintering. Two precursor synthesis pathways and two nitridation temperatures afforded nanopowders containing both (i) mixed AlN and GaN and (ii) such AlN and GaN admixed with Al0.5Ga0.5N as well as (iii) reference individual AlN and GaN. The applied sintering temperatures were either to preserve powder nanocrystallinity (650 degrees C) or promote crystallite growth and sintering-mediated Al0.5Ga0.5N formation (1000 degrees C). One specific route led to the novel nanoceramics of Al0.5Ga0.5N. The powders and nanoceramics were characterized by XRD, FT-IR, SEM/EDX, Al-27/Ga-71 MAS NMR, BET/BJH surface areas, and helium densities. Vicker's hardness tests confirmed many of the sintered composites and individual nitrides having high hardness comparable with monocrystalline AlN and GaN. Formation of pure Al0.5Ga0.5N nanoceramics was associated with closed pore evolution and had a detrimental effect on hardness.