Effects of Ba2+/Sr2+ ratio on the microstructure, dielectric and ferroelectric properties of BaxSr(1−x)TiO3 films prepared by micro-arc oxidation

BaxSr(1-x)TiO3 (BST) thin films are in situ deposited on a Ti matrix through the micro-arc oxidation technique, using a mixed aqueous solution of Ba(OH)2•8H2O, Sr(OH)2•8H2O and 0.05 M EDTA as the electrolyte. The influence of the Ba2+/Sr2+ ratio on the phase composition, microstructure and properties of the BST thin films is investigated. Ba0.6Sr0.4TiO3, Ba0.5Sr0.5TiO3, and Ba0.4Sr0.6TiO3 thin films have a cubic phase, while Ba0.8Sr0.2TiO3 and Ba0.7Sr0.3TiO3 thin films have a tetragonal phase. When the concentration of Ba2+ in the electrolyte surpasses that of Sr2+, the width of micro-arc holes and the surface roughness of the film grow as the Ba2+ concentration rises. Furthermore, the dielectric and ferroelectric properties of BST films are favorably connected with the surface morphology. When the Ba2+ concentration is 0.06 M, the film has the best compactness and smoothness. In addition, the highest capacitance and lowest dielectric loss are achieved.