Solid-State Electrochemical Thermal Transistors with Strontium Cobaltite-Strontium Ferrite Solid Solutions as the Active Layers

Thermal transistors have potential as thermal management devices because they can electrically control the thermal conductivity (lc) of the active layer. Recently, we realized solid-state electrochemical thermal transistors by utilizing the electrochemical redox reaction of SrCoOy (2 <= y <= 3). However, the guiding principle to improve the on/ off lc ratio has yet to be clarified because the lc modulation mechanism is unclear. This study systematically modulates lc of SrCo1-xFexOy (0 <= x <= 1, 2 <= y <= 3) solid solutions used as the active layers in solid-state electrochemical thermal transistors. When y = 3, the lattice lc of SrCo1-xFexOy is similar to 2.8 W m-1 K-1 and insensitive to x. When x = 0 and y = 3, lc increases to similar to 3.8 W m-1 K-1 due to the contribution of the electron lc. When y = 2, lc slightly depends on the ordered atomic arrangement. Materials that are high electrical conductors with highly ordered lattices when the transistor is on but are electrical insulators with disordered lattices when the transistor is off should be well-suited for the active layers of solid-state electrochemical thermal transistors.