Double-sided Tl2Ba2Ca2Cu3O10 thin films based high temperature superconducting filter operating above 100 K

A high temperature superconducting (HTS) filter on double-sided Tl2Ba2Ca2Cu3O10 (Tl-2223) thin films is designed in this letter. High-quality double-sided Tl-2223 thin films are prepared on 10 × 10 × 0.5 mm3 LaAlO3 (001) substrate. The critical temperatures Tc of the films are 120 ± 1 K and the critical current densities Jc are 3–4 MA/cm2 at 77 K for both sides. X-ray diffraction θ-2θ scans and rotational ϕ-scans prove that the films are strongly textured with the c axis perpendicular to the substrate surface. A 3-pole band-pass filter is then fabricated on the Tl-2223 thin films with 4% relative bandwidth and a center frequency of 4.0 GHz. At 77 K, 100 K, and 102 K, the insertion loss in the passband is 0.088 dB, 0.21 dB, and 0.27 dB, respectively. These performances show that the proposed HTS filter is satisfying even when the operating temperature is above 100 K, which makes it possible to work in outer space without cryogenic systems.