Ionic conductivity study of CaF2: Nd single crystals

The electrical ionic conductivity of unirradiated and irradiated CaF₂: Nd crystals in the range of 60 to 800°C has been measured. The conductivity plot is basically divided into four parts, i.e., intrinsic and extrinsic unassociated, extrinsic associated, and extrinsic segregated regions. Activation energy (for unirradiated samples) in the extrinsic unassociated region is in the range of 0.69 to 1.20 eV depending on the doping concentration while for the intrinsic region, it is of the order of 1.89 eV. The conductivity in the extrinsic unassociated region increases with increase of Nd content in the sample. Also, the conductivity in the extrinsic region forγ-irradiated sample is higher than that for unirradiated one. In the intrinsic region, however, the conductivity is independent of dopant concentration orγ-irradiation. From these results it is surmised thatF ⁻ interstitials are the charge carriers in this region for CaF₂: Nd³⁺ system.