Efficient sol-gel techniques for fabricating ferroelectric ceramic thin films of desired properties

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PZT thin films were prepared on silica glass substrates from Pb(CH_3COO)_2 - 3H_2O - Zr(OC_3H_<7^n>)_4 - Ti(OC_3H_<7^i>)_4 - H_2O - CH_3COOH - CH_3OC_2H_4OH - n-C_3H_7OH solutions containing polyvinylpyrrolidone (PVP) via non-repetitive dip- or spin-coating. It was found that PVP and CH_3COO- are thermally decomposed at 250°- 320℃, leaving carbonaceous species, followed by the crystallization of Pb_3(CO_3)_2(OH)_2 around 350℃. The oxidation of the carbonaceous species occurred at around 360°- 460℃, then perovskite PZT was formed around 550℃. The film thickness was found to decrease greatly at 200°- 350℃, where thermal decomposition of PVP and CH_3COO- occurred. The films fired at 700℃ were rather porous and not very transparent. Pre-heating the gel films at 100°or 200℃ resulted in particulate microstructure with gaps between the particles, and at 350℃ caused crack formation, both of which further reduced the optical transmittance.PZT, BaTiO_3 and BaBi_4Ti_4O_<15> films were prepared on … More Pt/Ti/SiO_2/Si substrates by spin-coating using alkoxide solutions containing polyvinylpyrrolidone (PVP). Deposition and firing of the gel films were performed just once, not repeated. Crack-free, single-phase PZT, BaTiO_3 and BaBi_4Ti_4O_<15> films as thick as 2.2, 0.77 and 0.40 μm could be prepared, respectively, via non-repetitive spin-coating. The 2.2 μm thick PZT film exhibited P-E hysteresis with remanent polarization and coersive field of 21 μC cm^<-2> and 90 kV cm^<-1>, respectively. The dielectric constant of the PZT, BaTiO_3 and BaBi_4Ti_4O_<15> films were 370, 310 and 380, respectively, at 1 kHz.An aqueous solution-based dip-coating technique was presented for ceramic thin film deposition. Organic polymers with amide groups such as polyvinylpyrrolidone, polyvinyl-acetamide and polyacrylamide, incorporated in aqueous solutions of metal salts, were demonstrated to offer much better wetting of the substrates and gel film formability. Transparent, crack-free TiO_2 and ZrO_2 thin films 0.07 - 0.1 μm in thickness could be obtained from aqueous solutions of Ti(SO_4)_2 and ZrCl_2O, respectively, containing these organic polymers. Less