Predicting the Phase Stability of Sc1–xLn x PO4 (Ln = Gd–Lu, Y) Zircon-Structured Solid Solutions

The energies of mixing (interaction parameters) in the Sc1–xLn x PO4 (Ln = Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) systems have been calculated using Urusov’s crystal energy theory of isomorphous substitutions. The decomposition (stability) temperatures of the solid solutions have been plotted against the atomic number of the rare-earth elements at x = 0.01, 0.03, 0.05, 0.10, 0.20, and 0.50. The present results can be helpful in a search for host and activator compositions for new luminescence, laser, and other materials based on the zircon-structured rare-earth orthophosphates.