The effect of defect structure on electrical conductivity and thermoelectric power of La2-xSrxCuO4-delta at high temperatures

The electrical conductivity and Seebeck coefficient of La2-xSrxCuO4-delta w ith x = 0 similar to 0.30 were measured as a function of temperature betwee n room temperature and 1000 degrees C and oxygen partial pressure of 1 simi lar to 1 x 10(-4.5) atm. From the analysis of the relationship between the electrical conductivity and Seebeck coefficient, it was suggested that a ho pping conduction model and a degenerated band conduction one are applicable to electrical conduction of La2-xSrxCuO4-delta when electrical conductivit y is less than 30 S cm(-1) and more than 60 S cm(-1), respectively. Combini ng oxygen nonstoichiometry data with the electrical conductivity and thr Se ebeck coefficient, it was revealed that the electrical properties of La2-xS rxCuO4-delta at high temperatures are determined only by the Cu mean valenc e. The concentration of hole carrier is determined by the Cu mean valence a nd carrier mobility is not dependent of the oxygen nonstoichiometry nor the Sr content. Also revealed was that the Seebeck coefficient of La2-xSrxCuO4 -delta is determined only by the Cu mean valence. Although apparent continu ous relationship was observed between electrical conductivity, Seebeck coef ficient and the Cu mean valence, indicated was that the conduction mechanis m changes continuously from hopping conduction to degenerated band conducti on at the Cu mean valence of around 2.05 +.