Two kinds of nanocrystalline materials CaF2(grain fineness D =16nm) and Ca0.75La0.25F2.25(D = 11nm) possessing clean interfaces were prepared with the method of inert gas evaporation and pressed under ultra high vacuum, Their complex impedance spectra were meas-sured in detail in the temperature range of 31℃ to 530℃. The results show that (1) In the range of 300℃ to 530℃, both of the two kinds of nanocrystalline ionic solids obey the Arrhe-nius equation well; (2) Ionic conductivity of nano-CaF2 is about one order of magnitude higher than that of polycrystalline CaF2, two order of magnitude higher than that of monocrystalline CaF2, activation energy for ionic conduction, E=1.14eV; (3) Ionic conductivity of nano-Ca0.75La0.25F2.25 is 1(300℃)-0.6(525℃) order of magnitude higher than that of nano-CaF2, activation energy E is 1.00eV, somewhat lower than that of nano-CaF2, (4) When the temperature rises from 250℃ to 525℃ , the resistance of grains drops about one order of magnitude, but the resistance of interfaces descends monotonously over four order of magnetude. It is demostrated that migration of F- depends on diffusion among grains at temperature lower than 400℃, and also upon diffusion among interfaces at temperature higher than 450℃. To decrease grain fineness of materials to nanometer-size as well as to mingle fluoride with higher valence can increase the ionic conductivity obviously.
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