| Bi-2223 superconducting tape,as a high-temperature superconducting material,has great potentiality in the power transmission field.However,at the present stage,the critical current density?Jc?properties cannot reach the practical level.As is known to us,the longitudinal magnetic field effect is a phenomenon that Jc in the longitudinal magnetic field tends to be larger than that in the transverse magnetic field.The anisotropy of the upper critical magnetic field(Bc2)refers to a phenomenon that Bc2 is different under the differing directions of the applied magnetic field.The occurrence of these two phenomena is accompanied by the changing directions of the applied magnetic field and affects Jc properties of the superconducting tape.Therefore,the effects of the longitudinal magnetic effect and the anisotropy of Bc2 on Jc properties of Bi-2223 superconducting tape will be mainly discussed by means of studying Jc properties under different applied magnetic field?intensity and direction?and temperature,and then,find ways to improve Jc.In addition,the theoretical model of Bi-2223 superconducting tape was established by using the balance conditions of Lorentz force and pinning force.Then,the correctness of the theoretical model was testified by the experimental results.Through the experiment and theoretical model,the following conclusions are drawn:1.The decisive factor affecting Jc is the longitudinal magnetic field effect when the temperature is around 40 K.Then,the influence of the longitudinal magnetic field effect on Jc gradually weakens,on the contrary,the effect of the anisotropy of Bc2 on Jc gradually strengthens with the increase of temperature.Finally,the anisotropy of Bc2 becomes the crucial factor affecting Jc.2.Jc in the longitudinal magnetic field is increased by 1.25 to 13.25 times as compared with that of the transverse magnetic field.3.The component of the applied magnetic field on the c axis of crystal determines Jc of Bi-2223 superconducting tape within a certain range. |
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