Electrochemical Preparation of Barium Titanate Films at Ultra-Low Temperatures

Abstract

Preparation of BaTiO3 thin films on titanium substrates by hydrothermal-electrochemical methods at temperatures ranging from 80 to 200°C have recently been reported in literature. In the present work, polycrystalline, homogeneous, and electrically insulating films of BaTiO3 have been electrochemically synthesized at temperatures as low as 55°C. Effects of various electrochemical and thermodynamic parameters such as temperature, solution pH, electrolyte composition, current density, and atmosphere on phase stability and film characteristics have been investigated. Formation of BaTiO3 is favored only under highly alkaline conditions. This finding is consistent with the reported phase stability criteria for BaTiO3 in Ba-Ti-CO2-H2O system. Auger spectroscopic analyses with depth profiling indicate a titanium oxide layer, whose thickness depends on current density, acts as a precursor to BaTiO3. Use of highly oxidizing atmospheres promotes the formation of thick, well-crystallized and electrically insulating films of BaTiO3 at low temperatures. Films synthesized at 55'C exhibit a characteristic bilayer structure consisting of a large grained porous top layer above a fine grained and dense bottom layer. In contrast, the films prepared at higher temperatures are uniform, fine grained but porous. Preliminary experiments indicate the feasibility to electrochemically synthesize BaTiO3 at temperatures near 25°C.

Chemical aspects of solution routes to perovskite-phase mixed-metal oxides from metal-organic precursors

“…119 At temperatures as low as 55 °C, crystalline BaTiC>3 thin films were electrochemically deposited on Ti metal as the anode using barium acetate-sodium hydroxide solutions under an oxygen atmosphere. 121 The films were contaminated with a small amount of BaC03 which was derived from reaction of the electrolyte with atmospheric C02 (probed by AES depth-profile analysis).…”

Theoretical Modeling and Experimental Verification of Electrochemical Equilibria in the Ba−Ti−C−H2O System

“…These techniques involve chemical reactions among precursor materials in an aqueous environment. More recently, an electrochemical−hydrothermal technique has been developed to synthesize perovskite type titanate (BaTiO 3 , SrTiO 3 , and CaTiO 3 ) thin films on titanium substrates. − The success of these methods to produce the desired material with specific characteristics depends to a large extent on process parameters, such as pH, composition, electrode potential, and temperature. While several investigators worldwide currently are working on developing and improving methods to synthesize advanced ceramic powders and thin films, very few focused on studying the thermodynamic stability relationships in the relevant systems. , Such data are crucial to understand the interactions between precursors and other reactants, which ultimately govern the characteristics of the produced material.…”

Report of the Electrolytic Industries for the Year 1995

“…For example, the films were synthesized by the galvanostatic anodization of titanium in a solution of 0.4M barium hydroxide.234 Also, an electrochemical process was used to synthesize these films (approximately 1 pm thick) on titanium using nonalkali electrolytes at temperatures as low as 55°~. 235 Researchers have studied the optimum conditions for electrosynthesis of nitrosobenzenes bearing electron-withdrawing substituents using dc polarography, cyclic voltammetry, and the recording of current-voltage curves using mercury and carbon electrodes.236 Nanocrystalline cerium(1V) oxide powders were prepared electrochemically by the cathodic degradation of base by researchers at the-university of ~i s s o u r i~olla. 237 A flexible film of poly(N-vinylcarbazo1e)-polypyrrole composite with conductivity of 10 S/cm at room temperature was synthesized by laser-electrochemical polymerization.…”