High-Temperature Thermoelectric Properties of La-Doped Ba1-xSrxSnO3 Ceramics

Abstract

Perovskite-type La-doped Ba1-xSrxSnO3 ceramics were prepared by a polymerized complex method followed by a spark plasma sintering technique to examine the thermoelectric properties at high temperatures. For nominal compositions of (Ba1-xSrx)0.95La0.05SnO3 (x = 0.0 - 1.0), La-doped single phases were obtained for x = 0.0, 0.2, 0.4, but a very small amount of La2Sn2O7 was formed for x = 0.6, 0.8, 1.0 and the amount increased with increasing Sr content, indicating that the solubility of La for Ba/Sr site was smaller than 5 mol% for x ≥ 0.6. Dense ceramics with relative densities of 91 - 93 % were obtained for the Ba-containing samples with x = 0.0 - 0.8. Temperature dependence of the electrical conductivity σ and Seebeck coefficient S showed that each sample with x = 0.0 - 0.8 was an n-type degenerate semiconductor in the measured temperature range of 373 - 1073 K. The Sr content dependence of the σ and S values suggests that the electron carrier concentration decreased with increasing Sr content from x = 0.2 to 0.8, due probably to the decrease in the solubility of La for Ba/Sr site. The thermoelectric power factors S2σ were almost equal among the ceramics with x = 0.0 - 0.8 showing the values from 5.7×10-6 Wm-1K-2 to 1.1×10-4 Wm-1K-2 with increasing temperature, because of a trade-off relation between the σ and S values with respect to the Sr content.