High pressure–high temperature investigation of the stability of nitride spinels in the systems Si 3N 4–Ge 3N 4

Abstract

In this study, we used laser-heated diamond anvil cell techniques coupled with synchrotron X-ray diffraction to investigate the synthesis and stability of nitride spinels in the Si 3N 4–Ge 3N 4 system, at pressures close to 20 GPa and at temperatures up to >2000°C. The newly discovered nitride spinels were found to be stable over the entire pressure and temperature range studied. There is little incorporation of Si 3N 4 component in γ-Ge 3N 4, but we observed formation of a new ternary nitride spinel (Si x Ge 1− x ) 3N 4, with x∼0.6. The analysis of the X-ray patterns indicates that Si 4+, normally considered to be the smaller ion, is strongly partitioned into the octahedral sites in the spinel phase. Excess Ge 4+ ions may also occupy these octahedral sites in the experimental synthesis at high pressure and temperature.