Curve Fitting of Dielectric Constant and Loss Factor of ZrO2-Doped Barium Strontium Titanate for Application in Phased Array Antennas

Abstract

DC electric field effects on the real part of the relative dielectric constant and the loss factor of barium strontium titanate for application in phased array antennas have been studied. The real part of the relative dielectric constant of the specimens decreases with increasing applied DC field. The loss factor under bias DC electric field is slighter than the real part of the relative dielectric constant under bias DC electric field does. The tunability is about 50% for barium strontium titanate doped with 0.5 wt % ZrO2 content. Variation of field coefficient A and tunability with ZrO2 contents have the same trend as that of the grain size. The real part of the relative dielectric constant of ZrO2-doped barium strontium titanate decreases rapidly before 1.0 kV/cm and slowly after 1 kV/cm compared within the data obtained by the curve fitting with Johnson's model. Compared with the fittings with the Johnson's model, the fittings with the Heywang model exhibit a small deviation between the testing and fitting data at a high applied voltage level. There is a conduction loss mechanism other than the intrinsic dielectric loss for the dielectric loss under bias electric field.