The reliability of elastic electrode/graded thermoelectric substrate systems with the adhesive interlayer

The durability of thermoelectric (TE) devices is significantly influenced by the interfacial reliability. A model for analyzing interfacial stress in an elastic electrode bonded to a finite-thickness functionally graded TE substrate through an adhesive interlayer is proposed, in which the electric conductivity, the thermal conductivity, the coefficient of thermal expansion, and the shear modulus of the TE substrate vary exponentially in the thickness direction. The equilibrium equation and the Fourier transformation are used to obtain the governing integro-differential equation, which is then solved using the collocation method. The model investigates the impact of material inhomogeneity, geometrical parameters, and TE loads on the interfacial shear stress, the interfacial axial stress in the electrode, and the stress intensity factors. It is found that a reduction in electric conductivity and an increase in the coefficient of thermal expansion along the thickness direction result in a notable decrease in stress singularities at the electrode ends. Furthermore, it has been discovered that the adhesive interlayer with a smaller modulus can reduce interfacial stresses, which is consistent with the findings of previous experimental studies. All the results are expected to prove invaluable in the design of elastic electrode/graded TE substrate systems in real-world applications.