Abstract
Thermoelectric power and thermal conductivity have been measured as a function of temperature on ceramic YBa2 Cu3 O7δ exposed to fast-neutron fluences of up to 6×1018 ncm2. Irradiation causes large changes in the magnitude and temperature variation of the thermopower and, for the highest doses, results in a complete suppression of the peak in thermal conductivity that is characteristic of the nonirradiated 1:2:3 superconducting ceramics below Tc. The likely physical origin of the changes are the defects created in the structure by fast neutrons that drastically limit the mean-free path of phonons and the charge carriers.