RESPONSE TIME AND STABILITY CHARACTERISTICS OF PMMA-CONTAINING BARIUM TITANATE SENSORS

摘要

In the present study, porous barium titanate-based ceramics were evaluated as humidity sensors. Variations of mi-crostructure and conductivity with relative humidity were investigated for fabricated ceramics doped with La2O3. Several barium titanate compositions were prepared successively by solid-state synthesis. High-purity powders were mixed by ball milling and then the mixtures were dried, sieved, and cold pressed. Green samples were sintered at 1300 and 1500℃ for 2-6 h in air. The porosity was measured by the Archimedes principle. The phase composition was determined by x-ray diffraction. As-sintered surfaces were examined by a scanning electron microscope equipped with energy-dispersive spectroscopy. The average grain size was determined by the linear interception method. The response time and stability chacteristics of the sensing element were measured by a using two-probe measurement method under a humid environment. It was found that doping enhanced the conductivity of BaTiO_3. The addition of PMMA increased the conductivity and humidity sensitivity through pore development. Porous and dense samples were compared in terms of response time. It was concluded that the fabricated sensors were stable toward long-term drift for a period of 1 month.