Phases in the System Ba ₂ SiO ₄ ‐Ca ₂ SiO ₄

Abstract

The system Ba 2 SiO 4 ‐Ca 2 SiO 4 was studied by heating mixtures of Ba 2 SiO 4 and Ca 2 SiO 4 at 1723 K. Six distinct phases resulted; they were examined by both X‐ray diffraction and differential thermal analysis. The phases β ‐(Ba 0.05 Ca 1.95 )SiO 4 and α‐(Ba 0.15 Ca 1.85 )SiO 4 are isostructural with corresponding high‐temperature modifications of Ca 2 SiO 4 . The X phase (Ba 0.48 Ca 1.52 SiO 4 ) is orthorhombic, is a pure phase rather than a solid solution, and is defined for the first time in the present work. The T phase (Ba 1.31 Ca 0.69 SiO 4 ) is hexagonal and interpreted in terms of a unit cell with a doubled c parameter, in contrast with literature data.