Phase transition temperature and negative thermal expansion of Sc-substituted In2(MoO4)3 ceramics

A series of Sc-substituted In2Mo3O12 ceramics were synthesized by the chemical co-precipitation method. The results reveal that In3+ can be substituted by Sc3+ and form a single phase with high purity for all In2−xScxMo3O12 (x = 0, 0.3, 0.6, 0.9, 1.2 and 1.5) samples. The crystal structure of In2−xScxMo3O12 changes from monoclinic to orthorhombic symmetry with increasing Sc3+-content, confirmed by X-ray diffraction and Raman spectroscopy (Raman). With increasing concentration of A-site Sc3+ cations, the microstructure of In2−xScxMo3O12 becomes denser and the shape and size distribution of grains is more regular and uniform. The monoclinic-to-orthorhombic phase transition temperature of In2Mo3O12 is successfully decreased from 343 °C to room temperature via the substitution of In3+ by Sc3+. When x = 1.5, the occurrence of the monoclinic-to-orthorhombic phase transition for In0.5Sc1.5Mo3O12 solid solution is at around 7 °C. It has an average linear coefficient of thermal expansion of − 5.08 × 10−6 °C−1 in 25–600 °C. The phase transition results obtained by theoretical calculation using the framework of spin-polarized DFT accord well with the experimental evidences.