Crystal chemistry of β-Si3N4 solid solutions containing metal oxides

Phase equilibrium diagrams of Si₃N₄-metal oxides systems were reviewed. It was found that the solid solubility limits of different metal oxides in β-Si₃N₄ depends on the size and charge of the metal elements. A misfit factor was suggested to present these variables numerically. For some compositions in the systems Si,Al/N,O, Si, Be/N,O, Si,Al,Be/N,O and Si,Be,Mg/N,O the misfit factors were computed and plotted against the solubility limits. It was found that substantial amount of foreign atoms can be accommodated in the β-Si₃N₄ lattice when the misfit factor is small. When the misfit factor becomes larger, only small amount of foreign atoms enter the lattice. The results suggested that this method can be used to estimate the solid solubility limits of one or more metal oxides and nitrides in β-Si₃N₄.