Dimensional Dependence of Voltage Coefficient of Resistance (αv) for PMNPT Based Varistors

This paper describes design of a structured composite varistor (voltage variable resistor) exhibiting a positive voltage coefficient of resistance. This structured composite consists of a thick film resistor printed on a lead magnesium niobate-lead titanate substrate. In this device the variation of resistance due to an applied voltage is produced through the coupling of piezo electric strain to a thick film resistor. It has been found that this resistor can give rise to a positive voltage coefficient of resistance when used as a three terminal or four terminal device. A mathematical model is developed to establish the variation of resistance with an applied voltage. Dimensional dependence of voltage coefficient of resistance (αv) was investigated by varying the width of the thick film resistor while keeping its length constant. It was found that αv is inversely proportional to the width of the thick film resistor. © 2014, The Institution of Engineers (India).