Small polarons in ＄La_{2/3}TiO_{3-δ}＄

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The thermoelectric power and dc conductivity of ＄La_{2/3}TiO_{3-δ}＄ (δ=0.057, 0.07, and 0.16) were investigated. The thermoelectric power is negative between 80 and 350 K. The measured thermoelectric power of ＄La_{2/3}TiO_{3-δ}＄ increases linearly with temperature, in agreeent with the model proposed by C. Wood and D. Emin [Phys. Rev. B 29, 4582(1984)],and represented by A+BT. This temperature dependence indicates that the charge carrier in this material is a small polaron.There exists a linear relation between log(σT) and 1/T in the range of 200–300 K, the activation energies for small polaron hopping were 0.15, 0.21, and 0.24 eV for δ=0.16, 0.07, and 0.057, respectively. These properties are discussed in terms of a hopping process involving small polarons.This conclusion is confirmed theoretically. Based upon polaron energies obtained experimentally, several parameters relevant to small polaron transport in this material are estimated.
American Institute of Physicsの論文