Influence of Ag Doping on Thermal Conductivity and Magnetic Levitation of Single Grain YBCO Superconductors for High-Temperature Superconducting Maglev.

• Ag-doping is an effective way to enhance thermal conductivity and the superconductivity of YBCO superconductors. • The enhancement of thermal conductivity is limited. • Too much Ag 2 O doping will have a negative effect on superconductivity. • Ag-doping YBCO bulks are more suitable for applications which with a complex and varying external magnetic field like high-temperature superconducting maglev. Ag doping in (RE)Ba 2 Cu 3 O 7−δ [(RE)BCO] bulk high-temperature superconductors has been recognized as an effective way to improve the mechanical and superconducting properties of REBCO bulk superconductors for practical applications such as high-temperature superconducting (HTS) Maglev. Ag 2 O nanoparticles doped YBCO samples with different doping amounts (x , x varies from 0∼0.5 wt%) were fabricated by Top-Seeded Melt-Growth method (TSMG). The samples' steady-state thermal conductivity (λ) and the magnetic levitation force (F L) were measured by a testing platform under a similar condition to the HTS Maglev system. The effects of Ag 2 O doping on the λ and F L of single domain YBCO bulks have been systematically studied. The λ of the c -axis and the ab -plane were calculated through the steady-state heat flow method. We observed that λ increases distinctly when x ≥0.3 wt%. The doping amount of 0.3 wt% has been evidenced to be the optimal value, of which the λ of the c -axis and ab -plane are approximately 52% and 48% higher than the undoped one respectively. According to the results of the F L measurement, we found F L will increase while the relaxation rate of the F L will decrease by adding trace amounts of Ag 2 O nanoparticles in comparison to the undoped sample. This observation suggests that Ag-doping is an effective way to enhance thermal conductivity as well as the superconducting properties of YBCO superconductors for practical applications. [ABSTRACT FROM AUTHOR]