Effects of (KMn)3+ co-doping on the negative thermal expansion property of In2W3O12

Abstract

At room temperature, monoclinic In2W3O12 ceramics exhibits positive thermal expansion. However, it transforms into an orthorhombic phase above 253 ℃, and then stably exhibits negative thermal expansion (NTE). In this work, to improve the NTE performance and extend the NTE temperature range of In2W3O12, the KxMnxIn2-xW3O12(0≤x≤0.5) ceramics were synthesized via the solid-state reaction method. The effects of (KMn)3+ double cation co-doping on the composition, microstructure, and thermal expansion behaviors of In2W3O12 ceramics were studied using XRD, Raman, XPS, SEM, and TMA. The results show that (KMn)3+ cations can replace In3+ in In2W3O12 ceramics. As the (KMn)3+ doping amount increases, monoclinic In2W3O12 gradually changed into monoclinic KxMnxIn2-xW3O12. Meanwhile, the grains grow up and the density of KxMnxIn2-xW3O12 ceramics was increased. Pure monoclinic KxMnxIn2-xW3O12 ceramics were prepared when x rises to 0.25 and 0.4. Among them, the thermal expansion coefficient of K0.4Mn0.4In1.6W3O12 ceramics in 100–700 ℃ is as high as -17.83×10-6 ℃-1, which was significantly improved compared to In2W3O12 ceramics. In addition, the structural phase transition of In2W3O12 ceramics around 253 ℃ was gradually eliminated and the NTE temperature range was widened. Double cation (KMn)3+ co-doping effectively improves the NTE performance of In2W3O12.