Preparation and thermoelectric properties of CuAlO2 compacts by tape casting followed by SPS

Highlights: • Tape casting followed by SPS was used to prepare CuAlO₂ thermoelectric bulks. • Shear thinning effect increased the orientation degree of CuAlO₂ bulks. • Increased orientation degree and density improved thermoelectric performance. • ZT value of the CuAlO₂ bulks reached 0.042 when temperature was 973 K. -- Abstract: We applied a novel method of tape casting followed by spark plasma sintering (SPS) to prepare CuAlO₂ compacts. During the tape casting process, plate-like Al₂O₃ particles distributed along the flow direction of slurry under the action of the shear-thinning effect. It greatly elevated the orientation degree of the CuAlO₂ compacts formed during the following SPS. Meanwhile, the relative density of these compacts was also considerably increased due to the reduction in porosity. The green compacts and as-sintered compacts were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The thermoelectric properties including electrical resistivity, Seebeck coefficient, thermal conductivity, power factor, and the dimensionless figure of merit were measured. The results show that sample CuO-45-TC exhibited the highest thermoelectric performance with a ZT value of 0.042 at 973 K. The value should be the highest performance reported in the literature as far as we know. The remarkable increase in orientation degree and relative density should be responsible for the improvement in the thermoelectric performance of CuAlO₂.