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

At room temperature , monoclinic In 2 W 3 O 12 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 In 2 W 3 O 12 , the K x Mn x In 2-x W 3 O 12 (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 In 2 W 3 O 12 ceramics were studied using XRD , Raman, XPS, SEM, and TMA. The results show that (KMn) 3+ cations can replace In 3+ in In 2 W 3 O 12 ceramics. As the (KMn) 3+ doping amount increases, monoclinic In 2 W 3 O 12 gradually changed into monoclinic K x Mn x In 2-x W 3 O 12 . Meanwhile, the grains grow up and the density of K x Mn x In 2-x W 3 O 12 ceramics was increased. Pure monoclinic K x Mn x In 2-x W 3 O 12 ceramics were prepared when x rises to 0.25 and 0.4. Among them, the thermal expansion coefficient of K 0.4 Mn 0.4 In 1.6 W 3 O 12 ceramics in 100–700 ℃ is as high as -17.83×10 -6 ℃ -1 , which was significantly improved compared to In 2 W 3 O 12 ceramics. In addition, the structural phase transition of In 2 W 3 O 12 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 In 2 W 3 O 12 .