Preparation of Barium Titanate Films at 55°C by an Electrochemical Method

Abstract

Work by previous investigators has shown that BaTiO, films can be synthesized from solution over temperature ranges from 80°C to greater than 200°C. In the present work, electrically insulating crystalline films of BaTiO, have been electrochemically deposited on titanium substrates at temperatures as low as 55°C. Auger spectroscopic analyses with depth profiling indicate that a titanium oxide layer whose thickness is governed by current density acts as a precursor to BaTiO,. Formation of BaTiO, is found to be favored only in highly alkaline solutions. This is consistent with the phase stability reported for the Ba-Ti-C0,-H,O system at 25°C. Lower processing temperatures (55°C) favor the formation of thick, electrically resistive, and wellcrystallized BaTiO, films, apparently due to increased oxygen solubility in the electrolyte solution. Films produced at 100°C are much thinner and are electrically conductive due to fissures and pores in their microstructure. Initial studies on the effect of current density indicate the formation of thinner and porous films with thicker titanium oxide intermediate layers.

Electrochemical synthesis of barium titanate thin films

“…Viewed under the optical microscope, the film formed on the electropolished substrate appears uniform and mirror-like, whereas that on the chemically polished substrate has a matte type surface. However, the SEM photos show that the film in 3(a) appears continuous and compact with more uniform grain sizes whereas in 3(b), bigger particles are seen embedded on the film similar to those observed by Bendgale et al 7 Experiments with different conditions of polishing show that the microstructure is critically dependent on the treatment of the titanium anode before electrolysis. In all cases the film growth was not uniform on different parts of the film giving rise to etching patterns [ Fig.…”

“…[1][2][3][4][5] In an earlier communication 6 we have reported the formation of barium titanate thin films by the electrolysis of a titanium anode at temperatures under 100 ± C. The formation of barium titanate required that the pH of the solution was over 13. Following this, Bendgale et al 7 have reported the electrothermal synthesis of barium titanate at temperatures as low as 55 ± C with the addition of NaOH at low current densities for long time (maximum 2.5 mA͞cm 2 for 24 h). They have also found that the cell voltage remained less than or equal to 3 V during the reaction.…”

Hydrothermal synthesis of BaTiO3 thin films on nanoporous TiO2 covered Ti substrates

“…However, one of the problems encountered in the hydrothermal thin film growth was that there was an upper limit for the thickness of hydrothermal thin films. When the thickness of thin films reached about 0.25 mm after 8-12 h hydrothermal treatment, the thickness does not change even the reaction time was extended to several weeks [12][13][14][15].…”

BaTiO3 nanocrystals: Hydrothermal synthesis and structural characterization

“…However, whether the particle size of the crystalline phase of the Ti precursors is the key factor remains unclear. The effects of the synthesis temperature, the pH value of the reaction medium, and the Ba/Ti ratio on the particle size and morphology have also been investigated extensively [22][23][24][25], but different results were reported by various researchers. To control the growth of BT powders with the desired size and particle morphology, the reaction kinetics and crystallization mechanism of BT powders in the hydrothermal processing must be understood.…”