Hydrothermal synthesis of barium titanate thin film on titanium powder

摘要

Hydrothermal techniques have been used for several years for the preparation of fine powder barium titanate (BaTiO3) ceramic materials [1,2]. In recent years there have been also a number of reports where hydrothermal methods have been used for the synthesis of barium titanate thin films [3,4]. This technique has an advantage over sputtering and sol-gel techniques in that crystalline films can be obtained at lower reaction temperatures (100-250 °C). The reaction between the substrate and film results in strongly adherent films. In an earlier report, we described the preparation and characterization of crystalline BaTiO3 on titanium metal foils by the electrochemical, hydrothermal and electrochemical-hydrothermal techniques [5]. In this communication, we present the results of experiments to form, for the first time, a well-crystallized, uniform thin (0.05-0.2 ^m) film of BaTiO3 on each particle of Ti metal powder. The films are found to be more uniform when compared to those on Ti metal foil. The versatility of the hydrothermal technique allows the adaptation of titanium metal in any form, for example a high surface area sponge which can enhance greatly, the dielectric constant of the barium titanate film. This method of preparation has therefore, potential applications in the field of electrolytic capacitors, of which the Ta/Ta2O5 system is the most important [6]. Here, the insulating layers owe their large capacitances to a combination of extremely large surface areas and extremely small thicknesses.