Power factor improvement of delafossite CuAlO2 by liquid-phase sintering with Ag2O addition

Abstract

Thermoelectric delafossite (CuAlO2)1−x(Ag2O)x with 02O3, and additive Ag2O powders. The mixture is ground and then pressed with uniaxial pressure into pellets. Differential scanning calorimetry and X-ray diffraction spectroscopy show that the sintering temperature to synthesize delafossite CuAlO2 with Ag2O addition is below 1473 K. X-ray diffraction patterns show the major phase of delafossite 3R-CuAlO2 along with a trace amount of 2H-CuAlO2. A small amount of the Ag phase is present in the samples depending on the amount of Ag2O addition and sintering temperature. Energy dispersive spectroscopy and backscattered electron image analyses show that the Ag phase is segregated around the grain boundary. Liquid-phase sintering is used to explain the growth mechanism. The CuAlO2 samples with Ag2O addition obviously exhibit enhanced bulk density, grain size, and electrical conductivity. The highest power factor (PF), obtained by CuAlO2 with 2 at% of Ag2O sintered at 1373 K, is 8.23×10−5 W/(m K2) at 873 K. Hence, our findings show an improvement for delafossite CuAlO2 by Ag2O addition.