Role of Mg-B-O Nanostructural Inhomogenities on the Performance of Superconducting MgB₂

Abstract:

Auger and SEM studies show that with increasing of MgB₂ manufacturing temperature from 600÷800 °C to 1050÷1100 °C the Mg-B-O nanolayers which are present in the MgB₂ matrix transform into distinct dispersed Mg-B-O inclusions. On the other hand the sizes of inclusions of higher magnesium borides (MgB_x, x=7 ÷ 25) which are also present in the MgB₂ matrix. The tendency is observed in a wide range of synthesis pressures (0.1 MPa-2 GPa). The described structural transformations are accompanied by an increase in critical current density, j_c, in low and medium magnetic fields and by transition from the grainboundary to the point pinning. The Ti addition results in a further increase in j_c due to: Ti promotes the formation of higher magnesium boride inclusions and localization (or segregation) of oxygen in MgB₂ matrix, and, hence, facilitates the formation of a homogeneous MgB₂ matrix with lower oxygen content, but with an increased number of Mg-B-O and MgB_x pinning centers. At low synthesis temperature Ti absorbs hydrogen forming titanium hydrides, thus preventing the formation of MgH₂ and provides the material densification. The positive effect of Ti addition is connected with the high ability of Ti to absorb hydrogen, oxygen, and magnesium. The results of the critical current and AC loss study by transformer method using rings from MgB₂ are discussed.

• Periodical: Advances in Science and Technology (Volume 95)
• Pages: 156-161
• DOI: https://doi.org/10.4028/www.scientific.net/AST.95.156
• Online since: October 2014
• Authors: Tetiana Prikhna*, Michael Eisterer, Wolfgang Gawalek, Vladimir Sokolovsky, Artem Kozyrev, Viktor Moshchil, Harald W. Weber, Sergey Dub, Xavier Chaud, Valeriy Kovylaev, Vladimir Sverdun, Myroslav Karpets, Tetyana Basyuk, Nina Sergienko, Tatiana Serbenyuk
• Keywords: AC Losses Inductive Fault Current Limiter, Critical Current Density, High Pressure, Magnesium Diboride, Nanostructural Inhomogenities, Ti Addition

References

[1] V. Sokolovsky, V. Meerovich, I. Vajda, V. Beilin, Superconducting FCL: Design and Application, IEEE Trans. Appl. Superconduct., 14, No 3 (2004), 1990-(1999).

DOI: 10.1109/tasc.2004.830608

[2] N. E. Reimann, R. Cherkaoui, B. Dutoit, D. Djukic, G. Grasso, Simulation of the transient response of a high-Tc superconducting current limiter inserted in an electrical distribution system, IEEE Trans. Appl. Superconduct., 7 (1997) 836–839.

DOI: 10.1109/77.614633

[3] V. Meerovich, V. Sokolovsky, G. Jung, S. Goren, Inductive superconducting current limiter: state of art and prospects, Applied Superconductivity 1995, Inst. Phys. Conf. Series 148 (1995) 603–606.

DOI: 10.1109/77.402730

[4] T. Prikhna, ·W. Gawalek et al., Effects of High Pressure on the Physical Properties of MgB2 , J. Supercond. Nov. Magn., 24 (2011) 137–150.

[5] R. F. Klie, J. C. Idrobo,N. D. Browning,A. Serquis,Y. T. Zhu, X. Z. Liao, F. M. Mueller, Observation of coherent oxide precipitates in polycrystalline MgB2, Appl. Phys. Lett. 80 (2002) 3970-3972.

DOI: 10.1063/1.1481239

[6] T.A. Prikhna, M. Eisterer, H.W. Weber et al. Nanostructural inhomogeneities acting as pinning centers in bulk MgB2 with low and enhanced grain connectivity, Supercond. Sci. Technol, 27, No 4 (2014) 044013.

DOI: 10.1088/0953-2048/27/4/044013

[7] T. Prikhna, M. Eisterer, W. Gawalek et al. Influence of oxygen and boron distribution on the superconducting characteristics of nanostructural Mg-B-O ceramics, Solid State Phenomena, 200 (2013) 137-143.

DOI: 10.4028/www.scientific.net/ssp.200.137

[8] N. Hörhager, M. Eisterer, H. W. Weber et al. Journal of Physics: Conf. Ser., 43 (2006) 500.

[9] Y. Zhao,Y. Feng, C. H. Cheng et al. High critical current density of MgB2 bulk superconductor doped with Ti and sintered at ambient pressure, Appl. Phys. Lett. 79 (2001) 1154-1156.

DOI: 10.1063/1.1396629

[10] T. Prikhna, N. Novikov, Ya. Savchuk, et al. High-pressure synthesis of MgB2-based material with high critical currents, Innovative Superhard Materials and Sustainable Coatings. NATO Science Series. II. Mathemetics, Physics and Chemistry, 200 (2005).

DOI: 10.1007/1-4020-3471-7_6

[11] M. Eisterer, Calculation of the volume pinning force in MgB2 superconductors, Phys. Rev. B, 77 (2008)144524.

[12] T. Prikhna, M. Eisterer, ·W. Gawalek et al., Synthesis Pressure–Temperature Effect on Pinning in MgB2-Based Superconductors, J. Supercond. Nov. Magn., 26 (2013)1569–1576.

DOI: 10.1007/s10948-012-2001-7

[13] P. Kováč, I. Hušek, T. Melišek, T. Holúbek, Properties of stabilized MgB2 composite wire with Ti barrier, Supercond. Sci. Technol. 20 (2007) 771.

DOI: 10.1088/0953-2048/20/8/008

[14] V. Meerovich, V. Sokolovsky, T. Prikhna, W. Gawalek, T. Habisreuther, AC losses in high pressure synthesized MgB2 bulk rings measured by a transformer method, Supercond. Sci. Technol., 26, 035015, (2013).

DOI: 10.1088/0953-2048/26/3/035015