Abstract

Electrical conductivity of Na 0.005Ca 0.995F 1.995 and Y 0.008Ca 0.992F 2.008 samples containing 2 mol% CeO 2− x as the dispersed phase has been measured in the range 630 to 1030 K using an ac bridge at 1 kHz. The presence of the dispersed phase enhanced the conductivity of CaF 2 homogeneously doped with NaF. However, heterogeneous doping with CeO 2− x decreased the conductivity of YF 3-doped CaF 2. This suggests that preferential adsorption of F − ions to the CeO 2− x interface and the consequent creation of a space charge region with increased fluorine vacancies near the interface is the primary mechanism responsible for the enhancement of the conductivity of CaF 2 heterogeneously doped with CeO 2− x . By the synergetic effect of homogeneous and heterogeneous doping, the conductivity of polycrystalline CaF 2 can be enhanced by 4.5 orders of magnitude at 630 K.

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