Hysteresis Studies of Reactor-Irradiated Single-Crystal Barium Titanate

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Abstract
Nuclear reactor irradiation of single‐crystal BaTiO3 causes an increase in the coercive field (Ec) and a decrease in the remanent polarization (Pr). The magnitude of these changes, for a particular level of irradiation, depends upon the polarization state of the crystal during irradiation; crystals in the polarized state during irradiation are more resistant to radiation damage than are virgin crystals. The radiation damage rate is only slightly dependent upon crystal thickness. The magnitude of the change in Pr depends significantly, for irradiation levels below 1018 nvt (E>0.1 MeV) fast neutron flux and the associated 1010 rad (H2O) gamma dose, upon the particular loop for which data are reported; the first loop after irradiation indicates a damage accumulation but this damage is annealed by an external field in approximately 70 consecutive loops. The coercive field is relatively insensitive to irradiation until the total accumulated exposure mentioned above, but Ec increases in an asymptotic manner at levels which are about a factor of two or three greater. The changes in Ec and Pr are interpreted in terms of a radiation damage model involving a buildup of a space charge (with associated strain) due to the trapping of ionized carriers in the domain walls of the crystals.