[17a-D511-1~9] 22.1 Joint Session M "Phonon Engineering"

▲ [17a-D511-4] Active Layer for Solid-State Electrochemical Thermal Transistors II:
SrCoO_x−SrRuO_x solid solutions

〇(D)Zhiping Bian¹, Hiromichi Ohta² (1.IST-Hokudai, 2.RIES-Hokudai)

Keywords:Thermal transistor

Very recently, we realized solid-state electrochemical thermal transistors with thermal conductivity (κ) ON/OFF ratio of ~4 by utilizing phase transition of SrCoO_x by the redox treatment. Through the modulation of the active layer by SrCoO_x−SrFeO_x solid solution, we found that electronic thermal conductivity (κ_ele) and phase transition play a crucial role to increasing the ON/OFF ratio of SrCoO_x-based thermal transistors. In order to study the properties of SrCoO_x-based thermal transistors more in-depth, we tested SrCoO_x−SrRuO_x solid solution as the active layer.
Out-of-plane XRD patterns of the resultant films indicate the change in the lattice parameter c upon redox treatment becomes large with increasing x. Among them, only SrCo_0.7Ru_0.3O_y shows a transition from perovskite (P) to infinite-layer structure (IL). When x < 0.3, SrCo_1−xRu_xO_y shows a transition from P to defect perovskite (DP) phase. However, when x > 0.3, SrCo_1−xRu_xO_y shows a robust P phase during redox treatment. κ for oxidized SrCo_1−xRu_xO₃ shows decreasing trend first and then increasing with x = 0.5 as the boundary. It would be because of the [RuO₆]−[CoO₆] octahedra having charge transfer interaction, which can make the structure stable (Co⁴⁺ → Co³⁺ and Ru⁴⁺ → Ru⁵⁺). Regarding to the reduction state, κ decrease due to heavy ion substitution when x = 0.1. When x > 0.1, DP changes to IL, this results in an increasing trend of κ.