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- Title
Thermoelectric Responses in Layered Strontium-Niobates Via Two Ways of Charge Carrier Control Techniques.
- Authors
Sakai, Akihiro; Kanno, Tsutomu; Takahashi, Kouhei; Omote, Atsushi; Adachi, Hideaki; Yamada, Yuka; Zhou, X.-D.
- Abstract
We have systematically examined the thermoelectric properties of the perovskite-related layered strontium-niobates Sr n Nb n O3 n+2 ( n = 4, 4.33, 4.5, and 5) and Sr2− x La x Nb2 O7, prepared using two charge carrier control techniques. Both have a similar anisotropic crystal structure that gives all the samples prepared a relatively low thermal conductivity. However, the two systems show very different behaviors with respect to Seebeck coefficient and resistivity. In Sr n Nb n O3 n+2, an n-driven semiconductor-metal transition occurs between n = 4.33 and 4.5, with highly metallic properties observed in their magnitudes and temperature dependence at higher values of n. We also observed the microstructures to gain a further understanding of their properties, and elucidated the unconventional charge distribution in the intermediate n = 4.5 material. By contrast, in Sr2− x La x Nb2 O7, thermally activated behaviors were displayed even in heavily La-doped materials. Strong electron lattice interactions due to low symmetric NbO6 octahedra appeared to be present over the whole doping range, with Sr2− x La x Nb2 O7 showing a lower electrical conductivity than metallic Sr n Nb n O3 n+2. However, the ZT of Sr2− x La x Nb2 O7 is one order of magnitude larger than for Sr n Nb n O3 n+2 due to the much larger Seebeck coefficient, and increased up to 0.048 at room temperature on increasing the La dopant level.
- Publication
Journal of the American Ceramic Society, 2012, Vol 95, Issue 5, p1750
- ISSN
0002-7820
- Publication type
Article
- DOI
10.1111/j.1551-2916.2012.05169.x