Tuning the phase transition temperature of Cr2(MoO4)3 by A-site substitution of scandium

A series of Cr2-xScx(MoO4)3 solid solutions with tunable monoclinic-to-orthorhombic phase transition temperature have been synthesized via solid-state reaction. X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) results show that all synthesized Cr2-xScx(MoO4)3 (0 < x ≤ 1.4) solid solutions are single phased with no impurities identified, which reveals that Cr3+ has been substituted by Sc3+ in Cr2(MoO4)3. Monoclinic to orthorhombic phase transition temperature of Cr2-xScx(MoO4)3 can be effectively tuned from 372 °C to room temperature as the substituted Sc3+-content (x) varies from 0 to 1.4. The synthesized Cr0.6Sc1.4(MoO4)3 crystalizes in an orthorhombic structure at room temperature, exhibiting anisotropic negative thermal expansion throughout the testing temperature range. The coefficient of thermal expansion measured by thermal mechanical analyzer (TMA) for Cr0.6Sc1.4(MoO4)3 is −11.17 × 10−6 °C−1 in the testing temperature range of 30–600 °C. Moreover, the crystallization, micromorphology, density and coefficient of thermal expansion of Cr0.6Sc1.4(MoO4)3 are obviously sensitive to the twice sintering temperature, whereas none of such sensitivity is found for the phase transition temperature.