Thermal conductivity of YBaCuO bulk superconductors under applied field: effect of content and size of Y211 phase

The temperature and magnetic field dependence of the a-axis thermal conductivity kappa(a) of YBaCuO bulk superconductors has been measured as a function of the content and the size of Y2BaCuO5 (Y211) impurity phase particles. In the specimen with the high critical current density J(c) the kappa(a)(T) enhancement below the superconducting transition temperature T-c is drastically suppressed in comparison with that of the lower J(c) specimens with smaller Y211 content or with larger Y211 particle size. In the YBaCuO bulk system, Y211 particles are efficient phonon scatterers as well as the main flux pinning centers and a clear correlation between the flux pinning and the phonon scattering strength has been confirmed. (C) 2003 Elsevier B.V. All rights reserved.