Mixing energies (interaction parameters) and decomposition temperatures in solid solutions of monazites of rare earth elements with structure La1–x Ln x PO4

Abstract

The mixing energies (interaction parameters) of solid solutions in orthophosphates La1–x Ln x PO4 of rare earth elements (REE) with monazite structure are calculated within the framework of the crystal energy theory of isomorphous replacement. Their values and contributions to the mixing energy depending on the size of replaceable structural units and the degree of ionicity of the chemical bond within the row of lanthanides from Ce to Dy expectedly increase. Accordingly, there is an increase in critical temperatures of solid solution decomposition (stability). This agrees with the previous results of ab initio quantum chemical calculations.