Crystal structures and thermal expansion of Yb2Si2O7–Gd2Si2O7 solid solutions

Solid solutions within the Yb2Si2O7–Gd2Si2O7 system were synthesized by a solid state reaction route and characterized for their structural and thermal properties. Incorporation of Gd2Si2O7 into Yb2Si2O7 resulted in multiple phase transformations, with the solid solutions exhibiting the monoclinic β-RE2Si2O7, monoclinic γ-RE2Si2O7, and orthorhombic δ-RE2Si2O7 crystal structures. The stability of crystal structures with additions of Gd2Si2O7 are attributed to space filling and minimization of molar volume. The thermal expansion coefficients (CTE) of the β and γ structures were largely unchanged by the addition of Gd2Si2O7 to the lattice, although the orthorhombic Yb2Si2O7–Gd2Si2O7 solid solution exhibited slightly less anisotropy in CTE of the lattice directions (25°C–1500°C) than undoped orthorhombic δ-Gd2Si2O7. [Display omitted] •Crystal structures and thermal expansion coefficients of solid solutions in the Yb2Si2O7–Gd2Si2O7 system were explored.•Monoclinic Yb2Si2O7 (space group C2/m) can accommodate up to ∼20 ​mol% Gd2Si2O7.•Additions of 30 ​mol% Gd2Si2O7 resulted in a monoclinic Yb1.4Gd0.6Si2O7 (P21/c) solid solution.•There is ∼40 ​mol% solubility of Gd2Si2O7 into Yb2Si2O7 and ∼40 ​mol% of Yb2Si2O7 was estimated to be soluble in Gd2Si2O7.•Thermal expansion coefficients in this system are more sensitive to changes in crystal structure rather than cation species.