Electrical characterization of PTC thermistor based on chromium doped vanadium sesquioxide

Chromium-doped vanadium sesquioxide based ceramic [(V1−xCrx)2O3] is investigated to understand its properties as a positive temperature coefficient (PTC) thermistor. This material has a very low electrical resistivity (10−5 Ω m−1) it is normal state compared with the other PTC materials (10−2 Ω m−1). It utilizes the bulk metal-semiconducting transition and enables protection against high currents. The synthesis process has taken place in a controlled atmosphere of oxygen pressure. The electrical contacts were made by Cr/Ag sputtering deposition method. At first this report describes the experimental procedures used for the characterizations. In the static measurements (thermal equilibrium), cycling through the PTC transition leads to a stabilisation of the resisitivity-temperature characteristic. The influence of microstructure upon electrical parameters stabilisation and the effect of the final heating temperature on the hysteresis form are discussed. A very small modification of the oxygen stoichiometry has an important influence on the high and low temperature transition in this material. In the dynamic measurements, the behaviour of the sample under short-circuit loads (current density up to 2000 A cm−2) are described and discussed. The evolution of the PTC sample under high current experiments shows a competition between the PTC thermistor behaviour of the low temperature zone and the negative temperature coefficient (NTC) resistance behaviour of the high temperature zone owing to the temperature distribution along the sample.