Current limiting phenomena in SmBa2Cu3O7 coated conductors observed by laser-induced thermoelectric imaging and low-temperature laser scanning microscopy

Abstract

SmBa2Cu3O7 (SmBCO) coated conductors were grown on IBAD-MgO templates the evaporation using a drum-in-dual-chambers (EDDC) deposition system. The material showed a critical temperature of 93 ̃ 94 K and a critical current of 200 ̃ 250 A/cm-width at 77 K in a self-field. The current-limiting properties and local structure of the films were examined by laser-induced thermoelectric (LITE) imaging and lowtemperature laser scanning microscopy (LTLSM). Surface morphology and chemical composition of the superconducting layers were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. A 100μm × 1mm-microbridgewas fabricated using a photolithographic technique and etching process. The measured LITE images of the SmBCO coated conductor showed that some grains on the surface, surface inhomogeneity, second phases, defects and tilted grains, cause different thermal gradients. The LTLSM images revealed twodimensional variations of local flux flow on the films as a function of the local critical current. The findings are consistent with the LITE images, indicating that both methods can visualize the local structures and phases. © 2010 IEEE.