A new technique to achieve thick Tl2Ba2CaCu2O8 films for advanced applications

Abstract

Tl2Ba2CaCu2O8 (Tl-2212) high-temperature superconductors (HTS) exhibit excellent superconductivity performance as their critical temperature (Tc) is higher than 100 K. However, the emergence of microcracks on the film surface restricts the thickness of the obtained Tl-2212 films, thus greatly limiting their scientific research and engineering application. Here, we fabricate crack-free Tl2Ba2CaCu2O8 (Tl-2212) films with a thickness of up to 5 μm on LaAlO3 (001) substrates synthesized by an improved strategy of a closed system. The impact of the thickness of the Tl-2212 films on their crystallographic orientations, Tc, critical current density (Jc) (0 T), critical current intensity (Ic) (0 T), and microwave surface resistance (Rs) was systemically explored. As the thickness increases, Tc values fluctuate slightly above 100 K while the variation of Jc follows the extended strong pinning theory. Ic of the 4 μm thick film stays around 80 A at 95 K, and the Rs result is less than 1 mΩ at 93 K, indicating their excellent performance at high temperatures. The interaction mechanism between the Jc and Rs of the Tl-2212 film is replenished in light of the quantitative exploration of Jc and Rs. This work on Tl-2212 films will promote their fundamental physics research and guide their potential applications in the electronics and electrical field. It can also serve as a reference for future research on other HTS materials.