Single-step dip coating of crack-free BaTiO3 films >1 μm thick:: Effect of poly(vinylpyrrolidone) on critical thickness

BaTiO3 coating films were prepared from Ba(CH3COO)(2)-Ti(OC3H71)(4)-H2O-CH3COOH-C3H7OH 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 BaTiO3 films >1 mu 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. High-molecular-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.