Low Temperature Electrochemical Synthesis and Dielectric Characterization of Barium Titanate Films Using Nonalkali Electrolytes

Abstract

Polycrystalline BaTiQ thin films of approximately 1 ~m thickness have been synthesized on Ti substrates by an electrochemical process using nonalkali electrolytes, at temperatures as low as 55~The effect of various processing parameters, such as solution chemistry, atmosphere, quality of substrate surface, applied voltage, temperature, and reaction time have been discussed. Film thickness and uniformity increase with reaction time up to 24 h. The quantity of total electric charge passed through the electrolytic cell is found to govern the film thickness and uniformity. Dielectric characteristics of the as-prepared and heat-treated films have also been reported. Use of tetraethylammonium hydroxide, a nonalkali base reagent to adjust solution pH, has resulted in films having improved dielectric properties as opposed to the films prepared with alkali metal bases such as NaOH. Heat-treatment further improves the dielectric properties through a phase transition to the thermodynamically stable tetragonal phase from the as-prepared pseudo-cubic phase as confirmed by the x-ray diffraction data.

Preparation and Characterization of Barium Titanate Electrolytic Capacitors from Porous Titanium Anodes

“…9,14,15 In the present work, based on the high dielectric loss, even under optimum processing conditions, it is believed that the intrinsic oxygen vacancies have a major role in contributing to the dielectric losses in the anodically derived materials. Thus, based on the current work and reports in the literature, [6][7][8][9][10][11] it is likely that barium titanate electrolytic capacitors, in a manner similar to tantalum and Fig. 10.…”

“…The use of barium acetate electrolytes to synthesize carbonate-free BaTiO 3 thin films on planar titanium substrates at an applied voltage of 3 V has been reported. 10 However, significantly larger electrolysis currents (100-200 mA) in the treatment of titanium anodes, compared to those of the planar substrates (5-25 mA), might have caused the breakdown.…”

“…To minimize dielectric losses in the films, the use of a nonalkaline electrolyte (tetraethylammonium hydroxide, TEAOH) to adjust solution pH has been recommended. 10 A lowtemperature (200°C) heat treatment of the synthesized films was reported to have increased the dielectric constant through a phase transition to ferroelectric tetragonal BaTiO 3 . 10 Based on the state of the art for synthesizing BaTiO 3 via anodic oxidation of titanium in barium-containing electrolytes and the technology developed for the fabrication of the solid tantalum electrolytic capacitors, the current work attempts to develop barium titanate electrolytic capacitors, as schematically shown in Fig.…”

“…The composition of the coating is dependent on the composition of the metal and the solution in which the anodization is performed, with cationic and anionic species incor-porated into the structure of the oxide. Many investigators [6][7][8][9][10][11] reported the synthesis of perovskite (ABO 3 ) complex oxides, such as BaTiO 3 , SrTiO 3 , and CaTiO 3 , and their solid solutions on titanium substrates using hydrothermal-electrochemical methods at temperatures in the range of 55°-300°C. This process involves the anodization of a titanium substrate in an electrolyte that contains the A-site ion (Ba 2+ , Sr 2+ , and Ca 2+ ) at elevated temperatures and pressures.…”

Low‐Temperature Electrochemical Synthesis of ZrO2 Films on Zirconium Substrates: Deposition of Thick Amorphous Films and in situ Crystallization on Zirconium Anode

“…A detailed formation mechanism is not clear, but in situ formation of several types of crystalline oxide films have been observed previously. [4][5][6][7][8][9][10][11] Crystallization of hydroxide on the anode is an interesting phenomena, but there is scant literature reporting crystalline ZrO 2 formation in weakly basic solutions at temperatures as low as 100°C. Electrochemical synthesis of ZrO 2 films or powders by the cathodic method have been attempted by Switzer and Phillips 22 and Gal-Or' and co-workers, 23,24 but only amor- Fig.…”