As. Skapin et al., Determination of the local electrical properties in ceramic materials gained by microcontact impedance spectroscopy, J EUR CERAM, 21(10-11), 2001, pp. 1759-1762
We used microcontact impedance spectroscopy with spatial resolution of abou
t few micrometers to study the influence of microstructure on electrical co
nductivity of two selected ceramic materials: (I) polycrystalline AgBr with
highly conductive grain boundaries and well-known bulk properties and (II)
LiMn2O4-carbon black composite which is of technological importance for li
thium rechargeable batteries. In the quantitative study of AgBr polycrystal
s we could easily separate grain conductivity from grain boundary conductan
ce. We found that the grain conductivity followed the behavior of single cr
ystals, while the grain boundary conductance exhibited single activation en
ergy in the whole temperature range studied. Comparing the results obtained
by microimpedance spectroscopy with conventional impedance spectroscopy, w
e showed that the brick layer model relates accurately the local electrical
properties to the overall sample's conductance. In the study of LiMn2O4-ca
rbon black composite we showed that if the carbon black coating was prepare
d by controlled deposition from dispersion, the electronic conductivity was
higher than that of the conventional composites prepared by mixing. Microc
ontact impedance spectroscopy shows that in the former case the distributio
n of the interfacial conductances (carbon black) is much narrower which exp
lains the percolation threshold observed already at very low carbon black f
ractions. (C) 2001 Elsevier Science Ltd. All rights reserved.