Preparation and properties of a capacitor structure formed by doubled-sided YBa₂Cu₃O_7-xfilms on SrTiO₃substrate

Abstract

The preparation of high-temperature superconducting YBa2Cu3O7-x thin films on both sides of the SrTiO3 substrate by DC magnetron sputtering is reported. The films on both sides of the substrate exhibited well-oriented crystalline structure with the c axis normal to the substrate surface, Tc=80-91 K and Rs less than 0.05 Omega at 77 K and 60 GHz. The properties of the resultant SrTiO3 capacitor with YBCO electrodes were examined at frequency of 1 GHz. The following parameters were obtained: relative dielectric permittivity of 4*103 at 77 K and dielectric loss tangents of 3*10-4 at 77 K. No hysteresis in the dependence of the capacitance on the DC bias voltage was observed.

Superconducting electrode capacitor based on double-sided YBCO thin film for wireless power transfer applications

“…Our future work will aim to develop a tunable HTS capacitor for WPT applications on the basis of the above findings and previous work regarding the SFS-based capacitor. For now, there is still a major obstacle for this type of capacitor (just as in [7,8]) to work directly with the HTS coil, forming a tunable resonator, since the DC bias voltage across the ferroelectric substrate would bring a short-circuit fault to the HTS coil in connection. To achieve the tuning of the HTS capacitor based on an all-superconducting resonator for WPT technology, our focus will be on overcoming this short-circuit problem.…”

“…In this paper, we propose an HTS capacitor based on double-sided YBCO thin film on a lanthanum aluminate (LaAlO 3 ) structure for WPT applications. In contrast to previous studies [7,8] performed on double-sided YBCO filmbased HTS capacitors, this work is the first attempt to apply this type of HTS capacitor to a WPT system. Besides capacitance, other important characteristics of a capacitor for WPT applications, including equivalent series resistance (ESR) and Q-factor, are also measured.…”

“…Some subsequent studies were performed on an HTS capacitor formed by YBa 2 Cu 3 O 7−x (YBCO) thin film deposited on ferroelectric substrate. It was found that the superconductor-ferroelectricsuperconductor (SFS) based capacitor had a capacitance dependence on the DC bias voltage [7,8]. In addition, there were other proposals for designing a capacitor with single-sided YBCO film [9][10][11].…”

A tunable superconducting LC-resonator with a variable superconducting electrode capacitor bank for application in wireless power transfer

“…Since the speed and cost of adjusting V b are much better, the electrical tuning method, rather than the thermal one, would be the optimal choice for the tunable resonator. In contrast to the metal-SrTiO 3 -metal structure, the YSY one is observed with no hysteresis loop of ε r (V b ) dependence, which is suitable for variable capacitors [20,21]. When the transmitter has the same resonant frequency of f=[L 2 C 2 (V b )] −0.5 /(2π) as the receiver by adjusting V b , Z 2 =R 2 and Z 3 =R 3 .…”

“…However, the superconducting resonators reported so far have no frequency-tuning functionality because of the fixed capacitance of developed capacitors. Variable HTS electrode capacitors based on a YBa 2 C 3 O 7−x (YBCO)-SrTiO -YBa 2 C 3 O 7−x (YSY) structure were revealed in [20,21]. Those capacitors, using incipient ferroelectric (or quantum paraelectric) materials with HTS electrodes, obtained a nonlinear permittivity dependence on the applied electric field with no hysteresis at a low temperature, whereby any DC bias voltage within the allowed adjusting range corresponds to a unique capacitance regardless of its regulating process (charging or discharging).…”