A four-probe ac apparatus for the high-resolution conductivity measurement of ceramic oxides at high temperatures

A simple nonbridge four-probe ac apparatus has been developed for the measurement of the electrical resistances of ceramic oxide samples in the range from 0.1 mΩ up to 1 Ω. Use of platinum press contacts enables performance up to 1000 degree C in oxidant gas atmospheres on pressed pellets as well as on thin layers on a substrate. The method allows for high-resolution measurements, 0.1% or better, at low measuring currents, typically 100 μA, and is insensitive to noise and environmental electromagnetic signals. The apparatus is relatively inexpensive and can be operated automatically by means of a personal computer. Results on the conductivity of platinum and of mixed lanthanum strontium manganite are given as an example