Electric transport measurements on bulk, polycrystalline MgB2 samples prepared at various reaction temperatures

9th International Workshop on Processing and Applications of Superconducting (RE)BCO Large Grain Materials

物理学;材料科学

Wiederhold, A.^1 ; Koblischka, M.R.^1 ; Inoue, K.^2 ; Muralidhar, M.^2 ; Murakami, M.^2 ; Hartmann, U.^1

Institute of Experimental Physics, Saarland University, Campus C 6 3, Saarbrücken

D-66123, Germany^1

Superconducting Materials Laboratory, Department of Materials Science and Engineering, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo

135-8548, Japan^2

关键词: Additional samples;    Bulk MgB2 superconductors;    Electric transport measurements;    Microstructure investigations;    Optimum processing;    Oxford instruments;    Polycrystalline samples;    Reaction temperature;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/695/1/012004/pdf
DOI  :  10.1088/1742-6596/695/1/012004

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

A series of disk-shaped, bulk MgB2superconductors (sample diameter up to 4 cm) was prepared in order to improve the performance for superconducting super-magnets. Several samples were fabricated using a solid state reaction in pure Ar atmosphere from 750 to 950oC in order to determine the optimum processing parameters to obtain the highest critical current density as well as large trapped field values. Additional samples were prepared with added silver (up to 10 wt.-%) to the Mg and B powder. Magneto-resistance data and I/V-characteristics were recorded using an Oxford Instruments Teslatron system. From Arrhenius plots, we determine the TAFF pinning potential, U0. The I/V-characteristics yield detailed information on the current flow through the polycrystalline samples. The current flow is influenced by the presence of pores in the samples. Our analysis of the achieved critical currents together with a thorough microstructure investigation reveals that the samples prepared at temperatures between 775°C and 805°C exhibit the smallest grains and the best connectivity between them, while the samples fabricated at higher reaction temperatures show a reduced connectivity and lower pinning potential. Doping the samples with silver leads to a considerable increase of the pinning potential and hence, the critical current densities.