Grain boundary conductance in AgCl gained by micro-contact impedance spectroscopy

Local conductivity of sintered AgCl polycrystals was studied using micro-co ntact impedance spectroscopy. The technique is based on the flux constricti on effect, which involves probing of the sample solely in the vicinity of t he microelectrode. By contacting the polycrystal surface at different point s, we could distinguish between the grains and the highly conductive grain boundaries. Temperature-dependent measurements revealed that the grain cond uctivity resembles that of single crystals, showing clearly the extrinsic a nd intrinsic behaviour. On the contrary, the grain boundary conductance exh ibits the same activation energy over the whole temperature range studied. These results go along with the ionic space charge model. Conductivity data obtained from micro-contact and conventional impedance spectroscopy allow a quantitative verification of the brick layer model. (C) 2000 Elsevier Sci ence B.V. All rights reserved.