Investigations of sol-gel-derived highly (100)-oriented Ba0.5Sr0.5TiO3: MgO composite thin films for phase-shifter applications

Sol-gel deposition of highly oriented Ba0.5Sr0.5TiO3:MgO composite thin films has shown desirable dielectric constant reduction and higher figure of merit for phase-shifter applications. In this multilayer configuration, MgO distributed homogeneously through the Ba0.5Sr0.5TiO3 (BST50) matrix, and it helped in tailoring the dielectric constant and reducing the loss tangent significantly. In the present study, the high-frequency dielectric behavior of the films has been evaluated by fabricating an eight-element coupled microstrip phase shifter and measuring the degree of phase shift and insertion loss as a function of applied voltage at room temperature. An increase in phase-shifter figure of merit (degree of phase shift per dB insertion loss) from 28 /dB for pure BST50 to 71 /dB for a BST50:MgO film (at 14 GHz and 333 kV/cm) has been observed. (orig.)