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 beta-RE2Si2O7, monoclinic gamma-RE2Si2O7, and orthorhombic delta-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 beta and gamma 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 degrees C-1500 degrees C) than undoped orthorhombic delta-Gd2Si2O7.