Dielectric properties of sol-gel derived barium strontium titanate thin films

Barium strontium titanate (BaxSr1-xTiO3) films were deposited by sol-gel technique on platinized silicon substrate for the composition range x = 0.0 to 1.0 in steps of 0.1. The as-deposited films were found to be amorphous. The films crystallize on annealing in air at 700 degrees C for 1 h, Dielectric constant (epsilon') and loss tangent (tan delta) were measured in the temperature range -180 degrees C to 150 degrees C in the frequency range 0.1 to 100 kHz. Both epsilon' and tan delta show a small dispersion for all the compositions. This dispersion is more at the peak value than at room temperature. A comparison of the room temperature and peak value of the dielectric constant for various compositions are made with the reported values. Transition temperatures are reported for the entire composition range. All the compositions show a transition from ferroelectric to paraelectric phase except strontium titanate. Transition temperature shows a systematic decrease with increase in strontium content. The variation is at a rate of 3.4 degrees C/mol% of SrTiO3, Curie constants are also reported for the entire composition range. (c) 2007 Elsevier B.V. All rights reserved.