Phase diagram of the Li ₂ SO ₄ –Na ₂ SO ₄ system

Abstract

Abstract The thermal analysis and X‐ray powder diffraction studies of the Li 2 SO 4 –Na 2 SO 4 system, including the high‐temperature X‐ray diffraction technique, have elucidated four phases of variable composition: three solid solutions based on the α‐Li 2 SO 4 , α‐Na 2 SO 4 , and α‐LiNaSO 4 high‐temperature polymorphs, and a low‐temperature β‐LiNaSO 4 phase. α‐Na 2 SO 4 ‐Base solid solution disintegrates into two phases via a monotectoid phase transformation. It is quite probable that the monotectoid process is related to the conversion of the second‐order phase transition to the first‐order phase transition.