The Study of Purity Improvement on Tl-1223 Thin Films by DC Sputtering and Post-annealing Method
Un-substituted TlBa2Ca2Cu3O x (Tl-1223)-superconducting thin films have been fabricated on a LaAlO3 (001) substrate in oxygen by using a two-step method, which includes direct current (DC) magnetron sputtering and post-annealing process. Thallium (Tl) content in amorphous precursor films is found to be important to the crystallization of Tl-superconducting phase. Using the nominal composition of Tl1+δ Ba2Ca2Cu3 O 8 (δ = 0.1∼0.2) precursor films, the formation is promoted to Tl-1223 and Tl-2223 phase rather than Tl-1212 and Tl-1223 phase with accompanying Tl-rich source pellets. When the annealing process continues, Tl-2223 phase will be converted to Tl-1223 phase at a suitable annealing time and temperature. From the X-ray diffraction pattern, only Tl-1223 (00l) peaks are observed, which shows that the purity of Tl-1223 film is improved significantly by this method. The critical temperature T c of Tl-1223 film is characterized at 110 K, and the critical current density J c (77 K, T = 0) is up to 1.5 MA/cm2.
KeywordsSuperconductor Tl-1223 Purity Anneal
Author acknowledges the support from the National Natural Science Foundation of China (51002081) and the Fundamental Research Funds for the Central Universities of China for this work.