Diffuse phase transitions, electrical conduction, and low temperature dielectric properties of sol-gel derived ferroelectric barium titanate thin films

Ferroelectric thin films of barium titanate were fabricated by sol-gel tech nique on platinum substrates. The processing temperature was 700 degreesC. The films obtained with a thickness of 1.5 mum were dense, transparent, and showed ferroelectricity. Scanning electron microscopy and x-ray diffractio n were used for studying the surface morphology and crystallographic struct ure of the film. Films in the metal-ferroelectric-metal configuration (MFM) were used for the electrical measurements. Dielectric constant and loss ta ngent were found to be 430 and 0.015, respectively, at 10 kHz under ambient conditions. The epsilon (')(T) curve shows broad peak centered around 120 degreesC as in the case of diffuse phase transition. The ac conductivity is proportional to omega (0.9) in the low frequency region and omega (1.8) in the high frequency region. The dc conductivity versus temperature curve sh owed a change in the slope around 125 degreesC, corresponding to the phase transition. To study the low temperature phase transitions, dielectric para meters on the films were measured to a temperature down to about 10 K. Rema nent polarization (P-r) and coercive field (E-c) obtained from the hysteres is loop at room temperature are similar to2.0 muC/cm(2) and similar to 27 k V/cm, respectively. Capacitance-voltage studies performed on the MFM struct ures showed butterfly loop at 135 degreesC. (C) 2001 American Institute of Physics.