Gas sensing properties of asymmetrically reduced Na1/2Bi1/2TiO3–based ceramics

Abstract We report the gas sensing properties of a type of new materials, Na1/2Bi1/2TiO3 (NBT)-based ceramics. After the NBT-based ceramics were asymmetrically reduced and coated with Au electrodes, the materials exhibit relatively large electrical responses when exposed to oxygen and some oxidizable gases at a relatively low temperature (≤300 °C). An electric voltage ∼60 mV is measured in the mixture of O2 and N2 (1% O2). In oxidizable gases, a negative response can be obtained. The measured voltages are −45 mV and −98 mV in the mixtures of H2/air (1000 ppm H2) and C2H5OH/air (1000 ppm C2H5OH), respectively. The electrical responses are proportional to the logarithm of the concentrations of the analyzed gases. Also, the electrical responses to oxygen and oxidizable gases have opposite signs, and the model of mixed-potential is proposed to explain the gas sensing phenomenon. This study provides a new material and a simple design for gas sensors. The proposed gas sensor comprises a reduced NBT-based ceramic wafer with the same electrodes on the opposite surfaces. Additional components in traditional gas sensors, such as sensing or reference electrode, are unnecessary.