Thermoelectric properties of Bi2Sr2Co2O9 whiskers under hydrostatic pressure

We report the temperature dependence of thermopower (S) in the ab plane of Bi2Sr2Co2O9 (BC-222) single crystalline whiskers under high pressure up to 1.2 GPa. Special modifications were made to our high-pressure transport measurement system to improve the measurement accuracy of S for whiskers with high resistance. Pressure improved the contact resistance dramatically. We observed a slight decrease of S and four-wire electrical conductivity (sigma) under high pressure. As a result, the power factor (S(2)sigma) was decreased less than 20% by pressure. From the temperature dependence of sigma, the band gap of BC-222 whiskers increase very slightly under high pressure. (C) 2002 American Institute of Physics.