The influence of firing temperature on the electrical and microstructural characteristics of thick-film resistors for strain gauge applications

Some commercial 10 kOmega/sq. 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 conductive phase in the resistors (RuO2, ruthenate, and a mixture of RuO2 and ruthenate) was determined with X-ray powder-diffraction analysis. The microstructures of the thick-film resistors were analysed with scanning electron microscopy, transmission 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 long-term high temperature firing (6 h at 950 degreesC) ruthenate transforms into RuO2 coinciding with a significant increase of the temperature coefficients of resistivity. (C) 2002 Elsevier Science B.V. All rights reserved.