Phonon scattering by 211 second phase grains in high T-c 123 bulk materials

Thermal conductivity of OCMG processed NEG123 bulk samples including 5, 10, 20, 30, and 40 mol% NEG211 second phase (SP) have been measured in the tem perature range between 15 and 150 K. Thermal conductivity enhancement below T-c was observed in all samples. Magnitude of both thermal conductivity an d its enhancement become smaller with increasing SP amount. It turned out t hat electronic contribution is smaller than 1% of total thermal conductivit y. We found a very strong correlation between magnitude of thermal conducti vity and the average distance between SP grains. Therefore, we can control the magnitude of thermal conductivity by added amount of SP. Critical curre nt density J(c) measured by SQUID magnetometer is larger than 2 x 10(4) A/c m(2) up to 3-4 T for the samples with 5, 10, 20, 30, and 40 mol% SP. From t hese results, these materials have very good characteristics for high curre nt power leads in relatively large stray field environment. (C) 2001 Elsevi er Science B.V. All rights reserved.