BaTiO 3 coating films were prepared from Ba(CH 3 COO) 2 -Ti(OC 3 H 7 i ) 4 -H 2 O-CH 3 COOH-C 3 H 7 i OH solutions containing poly(vinylpyrrolidone) (PVP) via single-step, nonrepetitive dip coating. The critical thickness-i.e., the maximum film thickness achieved without crack formation via nonrepetitive dip coating-was successfully increased by incorporation of PVP in the precursor solution. Relatively dense, crack-free BaTiO 3 films >1 m in thickness were achieved via single-step deposition using a solution containing PVP of average molecular weight of 630 000. Incorporation of an excess amount of PVP, however, led to a decrease in the critical thickness. Highermolecular-weight PVP was more effective in increasing the critical thickness, whereas N-vinyl-2-pyrrolidone monomers did not affect the critical thickness. Stepwise heating of the gel films resulted in increased optical transmittance of the films, accompanied by film densification.
BaTiO3 and PZT films were prepared by single-step dip-coating from alkoxide-acetate solutions containing polyvinylpyrrolidone (PVP). Crack-free BaTiO3 and PZT films over 1 μm in thickness were obtained via single-step deposition. Stepwise heating of the gel films was found to improve densification of BaTiO3 films, reducing the thickness and increasing the optical transmittance, which was not, however, the case with PZT films, where the stepwise heating rather induced crack formation, leading to degraded transmittance. Residual stress was evaluated on spin-coating BaTiO3 films by measuring the substrate curvature, where a significant reduction in tensile stress was found to be caused by PVP.
Achievement of Crack-Free BaTiO 3 Films over 1 µm in Thickness via Non-Repetitive Dip-Coating.-BaTiO 3 coatings on silica glass substrates are prepared from Ba(OAc) 2 -Ti (O-iPr) 4 -H 2 O-AcOH-iPrOH solutions containing poly(vinylpyrrolidone) with an average molecular weight of 630000. Crack-free films of 1.2 µm thickness are successfully grown by a single-step dip-coating process. SEM pictures show a relatively dense microstructure. The films are slightly opalescent in appearance, but transmit visible light. -
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