Study on the Microstructure and Dielectric Properties of Barium Strontium Titanate Thin Films Prepared by Sol-gel Method

Sr0.5Ba0.5–xBixTiO3 (BST) thin films were fabricated on a Pt/SiO2/Si substrate by the sol-gel method. Then follows an investigation of the influences of bismuth (Bi) on the microstructures and the dielectric properties of Sr0.5Ba0.5-xBixTiO3 (BST) thin films. The micro-structures of the BST thin films were examined by the XRD and the TEM techniques. Tetragonal perovskite crystal grains were observed in BST thin films. Increasing Bi3+ doping ration in BST will lead to decrease of the grain size. It is found that Bi3+ doping decreases the dielectric loss and improves the frequency dispersion of the BST thin films. Not only is compressed the peak of temperature-dependence of dielectric constant of Bi3+-doped BST thin films but also moves into the low-temperature region. Moreover, the average Curie tem-perature decreases gradually with the Bi3+ contents increasing.