Dielectric Properties and Leakage Current Characteristics of Sol-Gel Derived (Ba0.5Sr0.5)TiO3:MgTiO3 Thin Film Composites

(Ba_1-xSr_x)TiO₃ (BST) is a suitable material for microelectronic device applications due to its high response of the dielectric permittivity to an applied electric field. However, the large dielectric constants found in this system limit its usefulness at microwave frequencies. In our recent studies sol-gel prepared Ba_0.5Sr_0.5TiO₃:MgO heterostructured thin films have shown an increase in the figure of merit (tunability/loss) compared to pure Ba_0.5Sr_0.5TiO₃ films, but the leakage characteristics of these films did not improve significantly. Moreover, due to the hygroscopic nature of MgO, the BST:MgO heterostructured films may suffer with longer period of time instability. In this paper we used the low loss and non-hygroscopic MgTiO₃ for the fabrication of the Ba_0.5Sr_0.5TiO₃:MgTiO₃ (BST50:MT) heterostructured thin films by sol-gel technique and studied the effects of MgTiO₃ layers on the structural, physical, dielectric properties, and leakage current behavior of the BST:MT films. The X-ray studies indicated that both MT and Ba_0.5Sr_0.5TiO₃ are highly oriented and remain as two distinct individual entities in the composite films and a considerable reduction in the dielectric loss and leakage currents has been observed. High frequency phase shifter studies (at low voltage) suggest that these films are suitable for the tunable microwave device applications.