Interfacial behavior of a thermoelectric film bonded to a graded substrate

To improve the thermoelectric converting performance in applications such as power generation, reutilization of heat energy, refrigeration, and ultrasensitive sensors in scramjet engines, a thermoelectric film/substrate system is widely designed and applied, whose interfacial behavior dominates the strength and service life of thermoelectric devices. Herein, a theoretical model of a thermoelectric film bonded to a graded substrate is proposed. The interfacial shear stress, the normal stress in the thermoelectric film, and the stress intensity factors affected by various material and geometric parameters are comprehensively studied. It is found that adjusting the inhomogeneity parameter of the graded substrate, thermal conductivity, and current density of the thermoelectric film can reduce the risk of interfacial failure of the thermoelectric film/graded substrate system. Selecting a stiffer and thicker thermoelectric film is advantageous to the reliability of the thermoelectric film/graded substrate system. The results should be of great guiding significance for the present and upcoming applications of thermoelectric materials in various fields.