Thermoelectric power of Y0.6 Ba0.4 CuO3-x

The thermoelectric power of the high-temperature superconductor Y0.6 Ba0.4 CuO3-x was measured as a function of temperature between 77-300K. A change in sign of thermoelectric power was observed around 205K. This indicates that the charge carriers are predominantly electrons at temperatures above 205K and positive carriers below 205K, till the temperature reaches that corresponding to zero thermoelectric power.