Thermopower of High-Tc Materials; Inconsistencies and Anomalies

Attention is drawn to certain discrepancies, in both magnitude and T-dependence, between currently available data on the thermoelectric power, S, of the normal state of new high-temperature superconductive materials, —and, in particular, to the different values reported (in the same investigation) for La₂CuO₄, according, as it contains equal amounts of Ba or Sr. The importance of taking lattice perturbations into account in interpreting S-data is stressed, and expressions are given for S, assuming the carriers are Cu³⁺ holes introduced into the lower Hubbard band of the ideal parent material by divalent additives and/or deviations from stoichiometry.