Preparation of Sol-Gel Coatings by Electrophoretic Deposition
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this study,
ZrO2 coating for chemical and mechanical properties and
ferroelectric lead zirconate-titanate, PZT, films were prepared by electrophoretic deposition from sols obtained by hydrolysis of metal alkoxides in alcoholic solutions. The effects of deposition conditions on physical properties of the films were investigated as well as the deposition mechanism. EXPRIMENTAL PROCEDURES ZrO2 sols were prepared by hydrolysis of Zr(O-n-C 4 H9 ) 4 in ethanol with HNO 3 catalyst at room temperature. The concentration of Zr(O-n-C 4 H9 ) 4 was 0.15 mol/l. The molar ratios of [H201/[Zr(O-n-C 4 H9 ) 4 ] and [HNO 3 ]/[Zr(O-n-C 4 H9 ) 4] were 3 and o.2, respectively. The obtained sol was transparent. The viscosity of the coating sol, aged at room temperature for 2 h, was about 2.5 cp, and pH about 4.7. PZT sols were prepared by hydrolysis of Pb(O-iso-C 3 H7 ) 2 , Zr(O-n-C 4 H9 ) 4 and Ti(O-iso-C 3 H7) 4 in 1-propanol with acetylacetone at room temperature [4]. The molar ratio of Pb:Zr:Ti was 1:0.53:0.47. The molar ratio of [H2 0]/[total metal alkoxides] was 10. The concentration, viscosity and pH of the sol was 0.15 mol/l as PZT, about 5 cp and about 8.8, respectively. The obtained sol was transparent. Electrophoretic deposition was made at room temperature. The 95 Mat. Res. Soc. Symp. Proc. Vol. 346. 01994 Materials Research Society
transparent sols were used for coatings without any additive electrolytes. The substrate was placed between two counter electrodes in order to make coatings on both sides of the substrates. Plates of stainless steel, SUS304, or Pt-coated glass plates were used as substrates/electrodes. The substrates were cleaned by acidic solution and acetone vapor, and dried. The electrode distance was 1 cm. The applied voltage was I to 20 V, and constant voltage method was employed. Dip-coated films were prepared from the same sols. The withdrawal rate was about 5 to 12 cm/min. After drying at room temperature for 24 h, the weight of deposited films was measured. The thickness and the refractive index measurements were made by ellipsometry, at the wave length 632.8 nm. using an automatic ellipsometer (Shimadzu, AEP-100). X-ray diffraction measurements were made using a rotating sample holder for thin films (Rigaku, 2651AI) after drying and heat treating. PZT films were dissolved into HN03 solution, and the chemical composition was dtermined by inductively coupled plasma mass spectrometry, ICP-MS (Yokogawa Electric Co., PMS2000). The distributions of chemical composition were determined by electron probe microanalysis, EPMA (Shimadzu, EPMA-8705), in the direction parallel to the surface, and by Auger electron spectroscopy, AES (JEOL, JAMP-IOSX), and Ar ion etchi,•g in the direction perpendicular to the film surface.
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Fig. 2 Effect of deposition time, t, on electric current, i, amount of deposited film, w, thickness, d, and refractive index, n, of as-dried ZrO2 films (applied field; 2.5 V/cm).
Fig. I Effect of applied field, E, on electric current, i, amount of depo
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