Influence of Te doping on the perovskite manganite La0.5Ca0.5MnO3

摘要

Systematic studies of resistivity p, thermoelectric power (TEP) S, and thermal conductivity K have been performed on the perovskite manganite La0.5Ca0.5-xTexMnO3 (0 <= x <= 0.10). For the sample with x=0, S(T) exhibits a semiconducting behavior over the whole temperature range. However, for x > 0 samples, an obvious peak in S(T) curves is observed. It is found that the temperature dependence of both in S(T) and rho(T) in the high-temperature paramagnetic (PM) region follows the small polaron transport mechanism for all the samples. In the low-temperature insulating region, vatiable-range-hopping (VRH) model matches the experimental data better. But in the intermediate-temperature ferromagnetic (FM) region below Curie temperature T-C, rho(T) and S(T) of the samples with x > 0 are well fitted by the formula: rho = rho(0) + rho T-2(2) + rho T-4.5(4.5) and S = S-0 + S3/2T3/2 + S4T4, respectively, implying the importance of electron-magnon scattering. As to thermal conduction K(T), the low-temperature peak is suppressed due to Te-doping. The decrease Of K with increasing Te-doping is suggested to come from the combined effect of the scattering of the Mn3+O6 Jahn-Teller (JT) distortion and the disorder to the phonon and enhanced phonon drag effect. (c) 2006 Elsevier Ltd. All rights reserved.