The structure, thermal expansion and phase transition properties of Ho2Mo3−xWxO12 (x = 0, 1.0, 2.0) solid solutions

• The solid solution Ho2Mo3−xWxO12 was investigated by in situ X-ray diffraction.
• It is found that the substitution slightly influence thermal expansion property.
• A polymorph of Ho2Mo3O12 with Pba2 space group was observed above 700 °C.
• The W-substitution for Mo effectively suppresses this transformation.

Three solid solutions of Ho2Mo3−xWxO12(x = 0, 1.0, 2.0) were prepared by solid state reaction method, the temperature dependent in-situ X-ray diffraction and thermal analysis were performed to investigate their structure and thermal expansion. All samples have orthorhombic structure(space group Pbcn# 60) with negative thermal expansion at the room temperature. the substitution of W for Mo enlarges the lattice constant and slightly influences the negative thermal expansion. An irreversible phase transformation to the Pba2 phase(Tb2Mo3O12 structure) was observed at high temperature for Mo-rich samples. This ploymorphism could be effectively suppressed by the W-substitution for Mo, this phenomenon could be explained by the lower electronegativity of W6+ than Mo6+.

A polymorph with Gd2Mo3O12-type structure (space group: Pba2) for negative thermal expansion material Ho2Mo3O12 is observed above 700 °C, this polymorphism could be effectively supressed by W-substiution for Mo, the give the temperature dependence of Pba2 phase contents for Ho2Mo3−xWxO12 (x = 0.0, 1.0, 2.0).Figure optionsDownload as PowerPoint slide