Thermoelectric power of MgB 2

Abstract

Thermoelectric power (TEP) of MgB 2 and its changes with the superconducting transition temperature ( T c) have been investigated. MgB 2 samples synthesized with different techniques––sample 1 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 ∼300 K––were found to vary systematically with T c, consistent with the previously reported TEP changes in Mg 1− x Al x B 2. 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.