A transient triclinic crystal phase is identified during the crystallization of multi-component rare-earth disilicates. This transient phase has a density that is approximately 10% higher than that of the final monoclinic phase. This is critically significant in use of these materials in coating applications as the initial crystallization will result in large thermal stresses owing to this phase transformation. The technological implication of this is that utilizing scandium-rich compositions, which are less susceptible to the formation of the transient phase, is strongly encouraged.