Study On Humidity Sensing Prperties Of One-dimensional Nano-composite Metal Oxide Ba_x Sr_1-XTiO₃ Materials

Humidity is a physical quantity used to expresses the dryness degree of the atmosphere. Humidity sensor is a kind of widely used sensor in the large family of the chemical sensor. In recent years, with the rapid development of science and the gradually improved living standards of people, the demand for a high-powered humidity sensor has become urgent. Nano-material has many characteristics different from traditional materials because of their special structure such as: high surface-to-volume ratio, quantum size effect, interface effect, quantum tunneling effect etc. Therefore, the preparation and application of nano-materials have received more and more attention from many researchers both in domestic and international. The nano-composite metal oxide could be designed both in structure and scale, and the properties also could be improved by controlling the chemical composition. Accordingly, the humidity sensor based on nano-composite metal oxide could exhibit its transnormal superior characteristics.In this paper, nano-composite metal oxide Ba_xSr_1-xTiO₃ was synthesized by the method of sol-gel combined with electrospinning. And the resistive-type humidity sensor besed on ceramic substrate was preperaed. Many innovative achievements were obtained. The sensing mechanism was analyzed by combination of many methods. At last, the general approach of analysis the sensing mechanism of resistive-type humidity sensor was concluded and summarized based on the experimental results of this paper. The innovative results obtained in this paper were as following:1. Nine kinds (x is from 0.1 to 0.9) of Ba_xSr_1-xTiO₃ nanofibers were synthesized by the method of sol-gel combined with electrospinning. And then the fibers were analyzed by XRD and SEM methods. The results showd that the materials we synthesized exhibited the structure of perovskite and morphology of long one-dimensional fiber. The resistance-type humidity sensor based on Ba_xSr_1-xTiO₃ nanofiber was prepared. The results of electrical characteristics test to the sensor showd that the optimum working frequence was 100Hz. The sensor based on Ba_0.8Sr_0.2TiO₃ was the most sensitive to the change of environment relative humidity, and the complex impedance varied more than 4 orders of magnitude from 11% RH to 95% RH. The humidity hysteresis of this sensor was very small less than 1% RH. The response and recovery time of this sensor was about 8 s and 5 s respectively, when the relative humidity change from 11% RH to 95% RH. he sensing mechanism was analyzed by complex impedance spectra and ion conduction model.2. Orderd Ba_xSr_1-xTiO₃ nanofiber array was synthesized by repacking to the collection installation of electrospinning. The humidity sensing properties of the humidity sensor based on orderd BaTiO₃ nanofiber array was prepared. The results of electrical characteristics test to the sensor showd that the transmission of electron was benifited from the orderd Ba_xSr_1-xTiO₃ nanofiber array.Through the above aspects of this paper, we can conclude that the morphology change makes the humidity sensitive characteristics have been greatly improved when we make the traditional humidity sensitive material low-dimensional. This will open up a new way for develop and research high-performance humidity sensor, and also will find a new application field of one-dimensional nano-materials.