EVOLUTION OF RUTHENATE-BASED THICK-FILM CERMET RESISTORS

An experimental investigation has been carried out to study variations of microstructure, composition and electrical properties (sheet resis tance and its temperature coefficient) occurring in thick film (cermet ) resistors during the annealing process which transforms the initial ink into a resistive layer. Resistors based on Bi2Ru2O7 and a lead sil ica glass have been studied. Analyses have been performed on the inks using thermogravimetric measurements, and on annealed (fired) layers b y means of x-ray diffraction, atomic absorption, electron microscopy, microprobe analysis and other complementary techniques. The results po int out the role of exchange reactions and redox reactions inside the resistor body and emphasise the complexity of the phenomena which conc ur to define the final electrical properties of these resistive system s. Interrelations between microstructure, composition and electrical p roperties have been found and tentative explanations proposed.