Low loss tunable (Ba,Sr)TiO₃ ceramics utilizing intragrain concentration gradient

The miniaturization of electronic devices has led to a need for tunable dielectric materials. These materials must exhibit high tunability and low loss in the microwave region. We observed high tunability and low loss throughout the microwave region, from .3 MHz to 3 GHz, in (Ba,Sr)TiO₃ ceramics with intragrain concentration gradients. The tunability varied slightly with frequency and was measured to be approx. 10% at 3 GHz under 10kV/cm bias and the loss tangent remained virtually unchanged, below .02 in this region. Our data is consistent with the theory of ion hopping clusters. The graded composition results in suppression of ferroelectric resonance and thus dispersion of peak dielectric loss. The concept of intragrain concentration gradient materials can lead to a variety of applications in the microwave communications field.