Phonon scattering by 211 second phase grains in high Tc 123 bulk materials

Abstract 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 temperature range between 15 and 150 K. Thermal conductivity enhancement below T c was observed in all samples. Magnitude of both thermal conductivity and its enhancement become smaller with increasing SP amount. It turned out that electronic contribution is smaller than 1% of total thermal conductivity. We found a very strong correlation between magnitude of thermal conductivity and the average distance between SP grains. Therefore, we can control the magnitude of thermal conductivity by added amount of SP. Critical current density J c measured by SQUID magnetometer is larger than 2×10 4 A/cm 2 up to 3–4 T for the samples with 5, 10, 20, 30, and 40 mol% SP. From these results, these materials have very good characteristics for high current power leads in relatively large stray field environment.