Thermal transport in polycrystalline YBa2Cu3O7-delta,Y2BaCuO5 and melt-processed YBa2Cu3O7-delta materials

Simultaneous thermal conductivity and thermoelectric power measurements are reported for standard polycrystalline YBa2Cu3O7-delta (Y123) samples with oxygen contents covering the range 6.00 to 6.96 +/- 0.02, between 20-300 K. The resistivity of each sample over the same temperature range was also de termined and the data used to discuss the phonon and electron contributions to the total thermal conductivity in the normal state. The thermal conduct ivity and resistivity curves for both polycrystalline Y2BaCuO5 (Y211) and m elt-textured Y123 containing significant amounts of Y211 are used to discus s the insignificant effect of Y211 inclusions in polycrystalline Y123 on th e thermal conductivity curves in the vicinity of T-c. Longitudinal and tran sverse thermal Hall measurements on overdoped polycrystalline Y123 in magne tic fields up to 4 T have been used to verify that kappa (el)(xx) (B = 0, T ) shows a significant peak at similar toT(c)/2, while a two peak phonon con tribution is found in the thermal conductivity below T-c. The suppression o f the longitudinal thermal conductivity for the superconducting state by ma gnetic fields is also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.