Effect of Tb-doped Concentration Variation on the Electrical and Dielectric Properties of CaF₂ Nanoparticles

Calcium fluoride (CaF₂) nanoparticles with various terbium (Tb) doping concentrations were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and alternating current (AC) impedance measurement. The original shape and structure of CaF₂ nanoparticles were retained after doping. In all the samples, the dominant charge carriers were electrons, and the F^- ion transference number increased with increasing Tb concentration. The defects in the grain region considerably contributed to the electron transportation process. When the Tb concentration was less than 3%, the effect of the ionic radius variation dominated and led to the diffusion of the F^- ions and facilitated electron transportation. When the Tb concentration was greater than 3%, the increasing deformation potential scattering dominated, impeding F^- ion diffusion and electron transportation. The substitution of Ca²⁺ by Tb³⁺ enables the electron and ion hopping in CaF₂ nanocrystals, resulting in increased permittivity.