Microstructure and thermoelectric properties of Al-doped ZnO ceramic prepared by spark plasma sintering

The high thermal and low electrical conductivities of ZnO ceramics have hindered their thermoelectric appli-cations. The doping of ZnO with group 3 elements can enhance the thermoelectric properties. In this work, Al (2 at%) doped ZnO powder was sintered using spark plasma sintering at varying parameters (such as temperature (550-700 celcius), pressure (250-500 MPa) and the temperature of pressure application (Room Temperature (RT) and Holding Time (HT))). Maximum relative density of 98.9% was achieved at a temperature and pressure of 650 degrees C and 250 MPa, respectively. The Al-doped ZnO ceramics improved in electrical conductivity which caused a decrease in the Seebeck coefficient because of increased carrier concentration. The reduction in the grain size due to inhibiting growth effects of aluminum lead to a decrease in the thermal conductivity through phonon scattering at the grain boundaries. Hence, ZT of 0016 at 500 degrees C was obtained. This study indicated that Al-doped ZnO ceramics can be sintered at very low temperature of 650 degrees C. These conditions allow to retain the nano -structure, which is beneficial in improving the thermoelectric properties.

Automated summary

In this study, Al-doped ZnO ceramics were sintered at varying temperatures, pressures, and pressure application temperatures using spark plasma sintering. The ceramics achieved a maximum relative density of 98.9% at a temperature of 650 degrees Celsius and pressure of 250 MPa. The Al-doped ZnO ceramics exhibited enhanced electrical conductivity, decreased Seebeck coefficient, and reduced thermal conductivity, resulting in a ZT value of 0.016 at 500 degrees Celsius.