Interfacial reaction and thermoelectric properties of Sr0.9La0.1TiO3 ceramic diffusion bonding joints with different electrode layers

Abstract

n-Sr0.9La0.1TiO3 ceramic and Al2O3 substrate were welded by vacuum diffusion bonding with different electrode layers. Some intermetallic compounds could be observed at the interface when silver foil and nickel foil were applied as electrode layers. There was no obvious reaction product at the interface of joints when copper foil was employed as electrode layer. The joints fabricated using copper electrode layer showed the highest shear strength of 10.23 MPa. Furthermore, the thermoelectric properties of Sr0.9La0.1TiO3-20 wt %Ti/Cu joint were not significantly lower than that of intrinsic Sr0.9La0.1TiO3-20 wt %Ti thermoelectric material. In particular, the power factor value of Sr0.9La0.1TiO3-20 wt %Ti/Cu joint could reach 0.77 mW m−1 K−2 at 515 °C, which was 1.06 times that of intrinsic Sr0.9La0.1TiO3-20 wt %Ti thermoelectric material. After being aged in a vacuum environment at 675 °C for 15 days, the contact resistance of the SLT/Cu joint increased from 4.68 μΩ cm2 to 10.12 μΩ cm2, while the shear strength decreased from 10.23 MPa to 8.01 MPa. These results suggest that the interfacial properties, as characterized by contact resistance and shear strength, remained relatively stable and did not weaken significantly. The joints with copper electrode layer can meet the requirements of high-temperature application, which is beneficial to the production of high-temperature thermoelectric devices.