The (Ba1-xSrx)TiO3 (BST) system is well known for its high response of the dielectric constant to an applied electric field. However, the large dielectric constants found in this system limit its usefulness at microwave frequencies. A number of groups have used composite structures to dilute the dielectric constant and suppress the dielectric loss of BST for microwave applications. Typically, the low dielectric constant material MgO has been used as the secondary phase in the composites. In this work, we report on the dielectric properties of BST composites using the microwave dielectric MgTiO3 . Room temperature dielectric constants of <400 (measured at 1 kHz), and dielectric tunabilities of similar to 36% (at 20 kV/cm) have been achieved for the BST:MT composites. Due to the superior quality of these composite ceramics, large electrical breakdown fields in excess of 100 kV/cm are possible. High-field measurements indicate that the dielectric tunability of BST:MgTiO3 composites can be as high as 70% at 80 kV/cm.
