Impedance spectroscopic studies of sol–gel derived barium strontium titanate thin films

In the present work electroceramic thin films of barium strontium titanate (Ba1−xSrxTiO3 – BST) were deposited on stainless steel substrates by sol–gel technique. Homogeneous Ba0.6Sr0.4TiO3 thin films as well as spatially inhomogeneous BST thin films exhibiting artificial gradients in composition normal to the growth surface were deposited. Both up- and down-graded BST films were fabricated by depositing successive layers with Sr mole fraction x ranging from x = 0.5 to x = 0.3. In the present study the tool of impedance spectroscopy has been used to study the dielectric properties of BST thin films at room temperature. To analyze the impedance spectroscopy data the Nyquist (Z″ vs. Z′) plots as well as the simultaneous representation of the imaginary part of impedance and electrical modulus (Z″, M″) vs. frequency were used. Experimental data were fitted using the CNLS fitting method. Agreement between experimental and simulated data was established. The data indicated that the thin film samples fabricated can be represented by an equivalent circuit with two relaxation frequencies.