Electrical conductivity of La0.95Sr0.05F2.95 ceramics and crystals

Electrical transport in La0.95Sr0.05F2.95 crystals and hot-pressed, low-por osity, gastight ceramic was studied by impedance measurements as a function of frequency in the temperature range 293-700 K. Below 500 K, the total co nductivity of the ceramic is lower than that of the single crystal because grain boundaries impede ionic transport. Above 500 K, the conductivity of t he ceramic coincides with that of the single crystal to within the experime ntal accuracy, and the activation energy of conductivity is 0.25 +/- 0.02 e V. The conclusion is drawn that, at temperatures above 500 K, fast ionic tr ansport in the ceramic is no longer impeded by grain boundaries.