Solid solutions and ternary compound formation among Ge3N4-Si3N4 nitride spinels synthesized at high pressure and high temperature

Following the discovery of spinel structured silicon and germanium nitrides, we investigated the possibility of intermediate compositions or even solid solution in that new system. The multianvil syntheses were performed at 23 GPa and above 2000 degreesC. The synthesis products from a wide range of mixtures of low-pressure phases of Si3N4 and Ge3N4 gave rise to ternary silicon germanium nitride with the spinel structure. The results showed a complete solid solution between the two end members at the experimental conditions. The structure refinement also showed a strong site preference of silicon and germanium. The silicon atoms preferentially fill the octahedral sites and the germanium atoms preferentially fill the tetrahedral sites. Both gamma-Si3N4 and gamma-Ge3N4 were predicted to be wide band gap semiconductors. Therefore, the complete solid solution between those two end members could give rise to a new family of tunable wide band gap semiconductors.