Electrical properties of conductive materials used in thick-film resistors

Layers of conductive oxide powders (IrO2, RuO2 and Bi2Ru2O7) were prepared on alumina substrates by a thick-film technique. The films were fired at 875° C for different dwell times. The temperature dependence of resistance was measured in the range −196 to 850° C. SEM observations of the initial powders and the resistive layer surface after firing, as well as X-ray diffraction investigations, were carried out. The RuO2 and IrO2 oxides exhibit a high sintering ratio and the resistance of the fired layers increases with temperature as in the single crystal. The R(T) curve for Bi2Ru2O7 layers is in qualitative agreement with the polycrystalline material. The role of the grain surface area and the regions between the grains is dominant.