Thermoelectric performance of Dy/Y co-doped SrTiO3 ceramic composites with submicron A2Ti2O7 (A = Dy, Y) pyrochlore

Abstract

Dy/Y co-doped SrTiO3 ceramic composites with submicron A2Ti2O7 (A = Dy, Y) pyrochlore were in-situ synthesized by solid state method. The microstructure of the A2Ti2O7 phase and its relationship with thermoelectric properties of Sr0.9-xDyxY0.1TiO3 ceramics are studied. As the Dy content increases, the secondary phase content increases and the grain size slightly decreases from 1.03 to 0.77 μm, meanwhile, the grain size of main phase also decreases. The highest power factor of 1034.5μWK-2m-1 at 569 K has been obtained for x = 0.08 sample due to comparatively lower electrical resistivity. In addition, the introduction of Dy reduces the thermal conductivity dramatically by decreasing the grain size of main phase, increasing the number of second phase and enhancing the scattering of mass fluctuation. In the end, the zT > 0.20 is obtained within the range of size of 0.80 - 1.03 μm and the mass fraction of 4.91% - 13.50% for second phase. The maximum zT value of 0.22 has been obtained for x = 0.08 sample with the second phase size and the mass fraction of 0.88 μm and 11.6% respectively. Thus, heavy element doping and the second phase with right grain size and proportion can result in high thermoelectric properties for SrTiO3 samples.