Preparation and humidity-sensitive properties of nanocrystalline BaTiO3 thick film fabricated on Teflon substrate by using pressing method

Nanocrystalline BaTiO3 precursor has been synthesized by using the stearic acid gel (SAG) method. After calcining the precursor at above 600 °C for 0.5 h, nanocrystalline BaTiO3 powder with cubic perovskite structure is obtained. The powder is compacted further into solid material under a pressure of 0.1 to 2.0 GPa or fabricated into thick film by pressing on a Teflon substrate at room temperature and 200 °C. The powder and film samples are characterized by XRD, TEM and SEM. The results show that the average grain size of the powder is between 20 and 60 nm, and the thickness of the compacted film is about 56 μm. The investigation on the humidity-sensitive properties of nanocrystalline BaTiO3 thick film shows that a compacted thick-film sample possesses higher humidity sensitivity, simpler preparation process, and enhanced adhesion strength on the Teflon substrate in comparison with a coated sensor, and the grain size and pressing pressure have obvious influence on its properties. In addition, the solid reaction mechanism and pressure effect on the material in the course of processing are also discussed.