Synthesis of Layered Perovskites Ba_n+1Sn_nO_3n+1 by Coprecipitation Method and Their Thermoelectric Properties

Abstract

A series of layered perovskites Ba_n+1Sn_nO_3n+1 with n=integer was selected as a model oxide to elucidate correlation between the dimensionality of electrical conduction and the thermoelectric power factor. La-doped sintered bodies of Ba_2-xLa_xSnO₄ (n=1), Ba_3-xLa_xSn₂O₇ (n=2), and Ba_1-xLa_xSnO₃ (n=∝) were prepared by oxalate coprecipitation method and their electrical conductivity and Seebeck coefficient were measured at high temperatures. For the layered perovskites with n=1 and n=2, single phases of Ba_2-xLa_xSnO₄ and Ba_3-xLa_xSn₂O₇ with x=0.0-0.2 were obtained, in which the La atoms were doped into the rock-salt-type Ba site, but the conductivities were in insulating region, suggesting the localization of doped electrons. The doped perovskite Ba_0.95La_0.05SnO₃ with n=∝ showed n-type degenerate semiconducting behavior and the thermoelectric power factors were in the order of 10^-7 Wm^-1 K^-2, which should be increased by the improvement of sinterability.