Prediction of Isomorphous Substitution Limits and Thermodynamic Stability for Y1–xLnxVO4 (Ln = Ce–Lu, Sc) Solid Solutions with Zircon-Type Structure

Using Urusov’s crystal-energetic theory of isomorphous miscibility, the mixing energies (interaction parameters), critical decomposition (stability) temperatures and limits of isomorphous substitutions were calculated, and the areas of thermodynamic stability, instability and presumed metastability of solid solutions Y1–xLnxVO4, with zircon structure where Ln—rare earth elements (REE) and scandium were estimated. It was shown that the mixing energies and critical decomposition temperatures decrease significantly within the cerium subgroup and slightly increase within the yttrium subgroup with increasing REEs’ atomic numbers. Diagram of the thermodynamic stability of the solid solutions and domes of their decomposition for all systems Y1–xLnxVO4, Ln = Ce–Lu, Sc was presented. The results of this study can be useful in choosing the compositions of matrices and activators for new luminescent, laser and other materials based on solid solutions, including nanomaterials.