The Properties Of Humidity Sensor Based On (Na_0.5Bi_0.5)_0.94TiO₃-Ba_0.06TiO₃ Nanofibers/Mesoporous Powders

Humidity is closely related to people's life and production activities. Humidity sensor which is for detecting humidity has gained considerable attention. Humidity sensing properties depends directly on the humidity material, and more and more researchers are paying their attention to exploitation of materials for fabricating humidity sensor with excellent humidity sensing properties. The sensing properties of materials can be constrained by its size effect, changing the material microstructure can improve the humidity sensing properties of the material. In this paper, the(Na0.5Bi0.5) 0.94TiO3-Ba0.06TiO3(NBT-BT6) nanofibers and mesoporous powders are prepared by electrospun method and metal organic decomposition( MOD) method combined with nanocasting method. The humidity sensing properties of the samples are investigated. Analyzing the effect of material microstructure on the humidity sensing properties, and the humidity sensing mechanisms of samples are also studied.The two aspects of our study as follows:(1) The NBT-BT6 nanofibers are synthesized by electrospun and characterized by X-ray diffraction(XRD), field-emission scanning electron microscopy(FE-SEM),and transmission electron microscopy(TEM). The humidity sensor is fabricated by coating the NBT-BT6 nanofibers on a ceramic substrate with Ag-Pd interdigitated electrodes. At 100 Hz, the impedance of the humidity sensor based on the NBT-BT6 nanofibers changes more than five orders of magnitude when humidity changed from11% to 95% relative humidity(RH). The response time and recovery time are about 2s and 50 s, and the maximum hysteresis is around 5% RH. The results indicate that the NBT-BT6 nanofibers can be well applied to the preparation of high-performance humidity sensor.(2) The mesoporous NBT-BT6 powders are synthesized by MOD and combined with nanocasting methods and characterized by XRD, FE-SEM, and TEM. Then, the humidity sensor based on mesoporous NBT-BT6 powders is measured for its humidity sensing properties under different humidity conditions. By using the complex impedance plots combined with the morphology of materials, we discuss the humidity sensing mechanism based on mesoporous NBT-BT6 powders. The impedance of the mesoporous NBT-BT6 powders humidity sensor is obviously influenced by the frequency. At 100 Hz, the impedance of the humidity sensorchanges more than six orders of magnitude within the whole humidity range from11% to 95% RH. The orders of magnitude changed at 100 Hz were higher than other operating frequencies, and the impedance versus RH curve have the good linearity,namely 100 Hz is the best operating frequency, and the operating frequencies of 100 Hz are applied in all investigations hereinafter. The response time and recovery time are about 2 s and 55 s, and the maximum hysteresis is around 10% RH. The results indicate that the mesoporous NBT-BT6 powders are of great potential application for fabricating high-performance humidity sensors.