Electrophoretic deposition of pure and MgO-modified Ba0.6Sr0.4TiO3 thick films for tunable microwave devices

We report on the structural, dielectric, and optical properties of barium strontium titanate–magnesium oxide composite (BST-MgO) thick films fabricated by the electrophoretic deposition technique. The structure and morphology of the films were analyzed by x-ray diffraction and scanning electron microscopy, respectively. The films were optically characterized via FT-Raman spectroscopy. The dielectric measurements were conducted on metal–insulator–metal capacitors using platinum as the top and bottom electrodes. The typical small signal dielectric constants of Ba0.60Sr0.40TiO3 and Ba0.60Sr0.40TiO3–20 wt % MgO thick films, measured at an applied frequency of 1 MHz, were 603 and 327, respectively. The corresponding values of dissipation factor were 0.029 and 0.002, respectively. A high dielectric tunability of 17.3% was obtained for Ba0.60Sr0.40TiO3 thick films at an applied electric field of 20 kV/cm. The dielectric properties of the present thick films were comparable to those of the bulk ceramics; suggesting their suitability for high-frequency wide-band voltage-tunable device applications.