Thermal diodes, which allow heat flow in one direction but prohibit it in the reverse direction, are fundamental for thermal manipulation. Here, we report the construction of a thermal diode consisting of ${\mathrm{Ni}}_{0.85}{\mathrm{Fe}}_{0.15}\mathrm{S}$ (bonded with 10 wt % silver) and alumina. A high rectification factor γ of 1.51 is achieved with a relatively small temperature bias of 97 K near room temperature, indicating great potential applications in the field of nonlinear thermal control. The excellent rectification effect is attributed to the high contrast change in thermal conductivity of ${\mathrm{Ni}}_{0.85}{\mathrm{Fe}}_{0.15}\mathrm{S}$. In addition, we demonstrate that the maximum thermal rectification ratio is strongly dependent on the cold-terminal temperature of the thermal diode, the length ratio between the two segments, and the steepness of the first-order phase transition of ${\mathrm{Ni}}_{0.85}{\mathrm{Fe}}_{0.15}\mathrm{S}$.

• Received 6 February 2021
• Revised 11 June 2021
• Accepted 23 June 2021

DOI:https://doi.org/10.1103/PhysRevApplied.16.014031