Thermoelectric power of MgB2d

Thermoelectric power (TEP) of MgB2 and its changes with the superconducting transition temperature (T-c) have been investigated. MgB2 samples synthesized with different techniques-sample I by the encapsulation method and sample 2 by the high pressure and high temperature technique-showed different T-c (T-c of sample 1 = 38.7 K, and T-c of sample 2 = 40.4 K). The characteristic features of the TEP of these samples-low temperature linear behavior, deviation from the low temperature linear behavior at a certain temperature, and an almost saturating value at similar to300 K-were found to vary systematically with T-c, consistent with the previously reported TEP changes in Mg1-xAlxB2. These changes of the TEP behaviors with T-c in the superconducting diborides system are discussed in comparison with those of high T-c cuprates and bismuthates. The common feature of the saturating TEP at high temperatures suggests the importance of an anharmonic electron-phonon interaction. (C) 2003 Elsevier Science B.V. All rights reserved.