Pyroelectric and dielectric properties of sol-gel derived barium-strontium-titanate (Ba0.64Sr0.36TiO3) thin films

The barium-strontium-titanate (BST, Ba0(.64)Sr(0.36)TiO(3)) thin films have been prepared by the sol-gel method on a platinum-coated silicon substrate. The resulting thin films show very good dielectric and pyroelectric properties. The dielectric constant and dissipation factor for Ba0.64Sr0.36TiO3 thin film at a frequency of 200 Hz were 592 and 0.028, respectively. The dependence of the capacitance as a function of the voltage shows a strongly non-linear character, and two peaks characterizing spontaneous polarization switching can be clearly seen in this curve, indicating that the films have a ferroelectric nature. The capacitance changed from 495 to 1108 pF with the applied voltage in the -5 to +5 V range at a frequency of 100 kHz. The peak pyroelectric coefficient at 30 degreesC is 1080 muC/m(2) K. The pyroelectric coefficient at room temperature (25 degreesC) is 1860 muC/m(2) K, and the figure-of-merit of this film is 37.4 muC/m(3). The high pyroelectric coefficients and the greater figures-of-merit of Ba0.64Sr0.36TiO3 thin films make it possible to be used for thermal infrared detection and imaging. (C) 2002 Elsevier Science B.V. All rights reserved.