The investigation of thick-film resistors fired at different temperatures

Some thick-film resistors based on RuO2, ruthenates or a mixture of RuO2 and ruthenates, were evaluated. The resistors were fired at different temperatures to determine the influence of firing temperature on the electrical and microstructural characteristics. The microstructures of of the thick-film resistors were analysed with scanning electron microscopy and energy dispersive X-ray analysis. The temperature coefficients of resistivity, noise indices and gauge factors were measured as a function of firing temperature. After a long term high temperature firing ruthenate based conductive phase transform to RuO2 coinciding with a significant increase of the temperature coefficients of resistivity and decrease of the resistance. Glass phase in thick-film resistors was analysed by EDS. All glass compositions are rich in SiO2 with the molar ratio SiO2/PbO between 2 and 2.5. Subsolidus equilibria in the RuO2-PbOSiO2 diagram were determined with the aim to study possible interactions between conductive phase (either ruthenium oxide or ruthenate) and silica-rich glasses. The tie line between RuO2 and PbSiO3 indicates that the lead ruthenates are not stable in the presence of the silica-rich glass phase. (author)