Enhancement of Thermoelectric Performance of Sr 1− x Ti 0.8 Nb 0.2 O 3 Ceramics by Introducing Sr Vacancies

Donor-substituted strontium titanate is known as one of the best high-performance n-type oxide thermoelectric materials. In this work, Sr-deficient Sr1−xTi0.8Nb0.2O3 ceramics (x = 0, 0.01, 0.02, 0.03 and 0.04) were synthesized by solid state reaction, and the microstructural and thermoelectric properties were investigated to clarify the effects of Sr vacancies. By introducing Sr vacancies, the absolute Seebeck coefficient and electrical conductivity are enhanced simultaneously as compared with those of the sample without Sr vacancy, and thus the values of power factor are improved obviously. Although thermal conductivity increases after introducing Sr vacancies, thermoelectric performance of Sr1−xTi0.8Nb0.2O3 ceramic is enhanced notably because of the significantly enhanced power factor, and the figure of merit zT at 1073 K increases from 0.017 (of the sample x = 0) to 0.236 (of the sample x = 0.03).