Gauge factor of thick-film resistors: Outcomes of the variable-range-hopping model

Despite a large amount of data and numerous theoretical proposals, the microscopic mechanism of transport in thick-film resistors remains unclear. However, recent low-temperature measurements point toward a possible variable-range-hopping mechanism of transport. Here, we examine how such a mechanism affects the gauge factor of thick-film resistors. We find that at sufficiently low temperatures T, for which the resistivity follows the Mott's law R(T)∼exp(T₀^/T)1/4, the gauge factor (GF) is proportional to (T₀/T)^1/4. Moreover, the inclusion of Coulomb gap effects leads to GF∼(T0'/T)^1/2 at lower temperatures. In addition, we study a simple model which generalizes the variable-range-hopping mechanism by taking into account the finite mean intergrain spacing. Our results suggest a possible experimental verification of the validity of the variable-range hopping in thick-film resistors.