High-Temperature Thermoelectric Properties of La-Doped Ba_1-xSr_xSnO₃ Ceramics

抄録

Perovskite-type La-doped Ba_1-xSr_xSnO₃ 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 (Ba_1-xSr_x)_0.95La_0.05SnO₃ (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.