n-type as well as p-type semiconduction occurs in both "123" and "214" classes of oxide superconductors at elevated temperatures (600-850°C) as exhibited in plots of thermoelectric coefficient vs. logarithm of conductivity (Jonker plots). The similarity in high conductivity intercepts indicates similar conduction parameters (density-of-states, mobility) regardless of material or sign of charge carrier. The Jonker plot is a useful means of investigating the gradual transition from semiconducting to metallic behavior in these systems. © 1989.
Su, M. Y., Elsbernd, C. E., & Mason, T. O. (1989). n-type vs. p-type semiconduction at high temperatures in oxide superconductors. Physica C: Superconductivity and Its Applications, 160(2), 114–118. https://doi.org/10.1016/0921-4534(89)90178-0