Tunability and loss tangent of ferroelectric films in superconducting resonator

Using a high-temperature superconducting resonator, measurements of the dielectric properties of ferroelectric films at microwave frequency ( GHz) are performed. The variation in dielectric constant, , of film under the influence of an applied dc voltage, , at liquid-nitrogen temperature affects the value of the capacitance, C, and loss tangent, , of the ferroelectric capacitor. In order to evaluate the values of C and of the capacitor, we used the resonator which has a planar ferroelectric capacitor in the break of the microstrip line. The couplings of each microwave input and output port are designed in the resonator, including the bias circuits of the zero-field points. ferroelectric capacitors with values of the capacitance of about 0.5 pF and less than 0.01 successfully control the tunability of the resonance frequency in the resonator with a factor of .