Seebeck Coefficients of LnBa₂Cu₃O_7-y and High T_c Bismates at High Temperatures

Abstract

Seebeck coefficients (S) of LnBa₂Cu₃O_7-y(Ln=Sm, Eu, Dy, Ho, Er and Yb) and a nearly single phase Ca-substituted LuBa₂Cu₃O_7-y show the similar temperature dependences as S of YBCO, but have a tendency of decreasing of S values with increasing the atomic number of lanthanides; Ho-, Er-, Yb- and Lu-oxides show the negative S below 550 °C, implying that the dominant carriers are electrons. S of high T_c phase of bismates (2223 phase) is negative in a range 200-850 °C, which may also indicate the electron conduction.