Phase transition in sol-gel-derived barium titanate thin films

The phase transition in sol-gel-derived barium titanate thin films has been investigated. The room temperature dielectric constant ) and loss tangent of the films were found to be 400 and 0.01 respectively. The dielectric constant has a broad peak of lower magnitude at . The polarization-field relationship ( P - E ) had a saturated hysteresis curve at room temperature. The spontaneous polarization , remanent polarization and coercive field of the film determined from the P - E hysteresis were found to be , and respectively. The capacitance-voltage ( C - V ) and conductance-voltage ( G - V ) characteristics of the film also exhibit hysteresis. The coercive field determined from the C - V characteristic is slightly lower than that determined from the P - E hysteresis loop. The capacitance and conductance decreased with the dc bias even at temperatures well above the transition temperature.