Dielectric properties of rare earth fluorides LnF3 (Ln=La, Ce, Pr)

Results of experimental investigations of dielectric properties of LaF3, CeF3, PrF3 monocrystals within 100-600 K temperaure range are presented. Essential fluctuations are observed in 260-270 K range at the temperature dependence of permittivity but it has been failed to relate them with phase transition. Contribution of thermal ion polarization into permittivity is estimated. It is pointed out that permittivity dispersion is of relaxation character and is caused by jumps of fluorine weakly bond ions which are responcible for superionic conductivity in these crystals