NiO(Co0.25Mn0.75)2O3 and BaSrTiO3 thick films on alumina substrate as temperature and humidity ceramic multisensors

Abstract

NiO·(Co0.25Mn0.75)2O3(Mn-Ni-Co) and Ba0.5Sr0.5TiO3(BST) thick films were screen printed on Pt patterned alumina substrate to investigate the effects of sintering temperature on humidity and temperature sensing properties of ceramic sensors. A raise in sintering temperature increased resistance and B constant of the Mn-Ni-Co temperature sensor. This may have derived from the synergic effects of the reduction in charge carriers caused by the substitution of Co for Mn as well as the formation of microcracks from the difference in thermal expansion coefficients. Dependence of resistance on humidity of the Mn-Ni-Co temperature sensor, however, was not found. BST films sintered at temperatures in the range of 1100 ℃ to 1150 ℃ showed excellent humidity sensing properties. The BST humidity sensor was faster in its response than the Mn-Ni-Co temperature sensor. The humidity sensor, however, proved to be unstable under various temperatures, suggesting a need for a temperature stabilizing device. In contrast, the Mn-Ni-Co temperature sensor was stable under humid conditions.