Polarized XAFS Analyses for MgB2 Thin Films

Miyanaga, Takafumi; Matsumura, Ryo; Seo, Mami; Takeda, Kenta; Hatanaka, Daichi; Yoshizawa, Michito

doi:10.1007/s10948-017-3991-y

Cited by 6 publications

(4 citation statements)

References 11 publications

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“…Local structure studies using Raman spectra and EXAFS measurements have revealed the presence of local lattice distortion in MgB 2 films owing to the application of a ZnO buffer layer. , While the Mg–Mg bond ordering showed insignificant fluctuation, the Mg–B bond ordering was found to be heavily affected by the ZnO thickness . To find a correlation between the local structure distortion and the second pinning mechanism, renormalization of the Fourier transform of the Mg–B bond ordering with respect to the Mg–Mg bond ordering was measured by Mg K-edge EXAFS, for which the results are shown in Figure a. − Renormalization to the Mg–Mg bond was proposed to reduce the probability of miscalculation caused by the backscattering process and other disturbances. Based on the assumption that the local structural distortion affects the secondary pinning behavior, the p values of the pinning functions are plotted as a function of the relative bond ordering in Figure b.…”

Section: Resultsmentioning

confidence: 99%

“… 30 To find a correlation between the local structure distortion and the second pinning mechanism, renormalization of the Fourier transform of the Mg–B bond ordering with respect to the Mg–Mg bond ordering was measured by Mg K-edge EXAFS, for which the results are shown in Figure 6 a. 42 − 46 Renormalization to the Mg–Mg bond was proposed to reduce the probability of miscalculation caused by the backscattering process and other disturbances. Based on the assumption that the local structural distortion affects the secondary pinning behavior, the p values of the pinning functions are plotted as a function of the relative bond ordering in Figure 6 b.…”

Section: Resultsmentioning

confidence: 99%

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Enhancement in High-Field J_c Properties and the Flux Pinning Mechanism of ZnO-Buffered MgB₂ Films

Putra

Jung

et al. 2023

ACS Omega

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We investigated the flux pinning properties in terms of the critical current density (J c) and pinning force density (F p) of MgB2 films with ZnO buffer layers of various thicknesses. At higher thicknesses of the buffer layer, significantly larger J c values are observed in the high-field region, whereas J c values in the low- and intermediate-field regions remain largely unaffected. A secondary point-pinning mechanism other than primary grain boundary pinning is observed in the F p analysis, which depends on the thickness of the ZnO buffer layer. Moreover, a close relationship between the Mg and B bond ordering and the fitting parameter of secondary pinning is obtained, indicating that the local structural distortion of MgB2 induced by ZnO buffer layers with different thicknesses may contribute to flux-pinning enhancement in the high-field region. Discovering further advantages of ZnO as a buffer layer other than the delamination resistance it provides will help to develop a MgB2 superconducting cable with a high J c for power applications.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Enhancement in High-Field J_c Properties and the Flux Pinning Mechanism of ZnO-Buffered MgB₂ Films

Putra

Jung

et al. 2023

ACS Omega

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“…In the entire life of MgB 2 , MgO plays an essential role. The MgO exists not only in bulk samples [2], but also in wires and tapes [3], thin films [4], and even single crystals [5].…”

Section: Introductionmentioning

confidence: 99%

Systematic investigation into the effect of boron powder purified by different methods on the microstructures and superconductivity of MgB₂ bulks

Zhang

Tian

Yang

et al. 2019

Supercond. Sci. Technol.

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Commercial boron powder was purified by a heat treatment method and a chemical method, and the effect of the differently purified powders on the microstructure and superconductivity of MgB2 was systematically investigated. Both purification processes successfully decreased the oxygen content, but neither could completely eliminate oxygen in the boron powder. The significant degradation of MgO peaks and increase in superconductivity for the sample with heat treatment purified boron powder indicated the best purification performance. For comparison, MgB2 bulks with chemical purified boron powder were also investigated. The reason of incomplete purification on the oxygen and the reaction mechanisms for the differently purified boron powders during the synthesis of MgB2 were uncovered. This research provides an important foundation for understanding the reaction of oxygen during MgB2 synthesis, and thus finally reveals the effect of oxygen on superconductivity in this system.

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“…MgB 2 , a superconducting material with a 39 K transition temperature discovered in 2001, has attracted much attention worldwide, thanks to advantages such as weak link free grain boundaries, a large coherence length and low material cost [1]. MgO is an inevitable second phase constituent of synthesized MgB 2 , not only in bulk samples [2], but also in wires and tapes [3], thin films [4] and even single crystals [5].…”

Section: Introductionmentioning

confidence: 99%

A novel gas–solid reaction process to synthesize low oxygen MgB₂ powder using Mg vapour

Zhang

Tian

et al. 2018

Supercond. Sci. Technol.

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We have established a novel reaction process using Mg vapour and B powder (a gas–solid reaction) to synthesize MgB2 powder with a low oxygen content. For the first time, we tried to eliminate the oxygen in Mg powder with a specially designed furnace tube that can keep the sample under an inert atmosphere throughout the entire synthesis process. The duration of heat treatment has a conspicuous effect on the phase formation of MgB2 which differs greatly from the conventional solid state reaction method. At short durations such as 1 h, unreacted B powder is ubiquitous in the sample. Full formation of MgB2 is achieved at 3 h. At longer times such as 4 h, MgB2 decomposes to form MgB4. It is deduced that the main reason for the unstable MgB2 phase formation in the gas–solid reaction is the Mg vapour present during the entire process. A feasible chemical reaction model of the novel gas–solid reaction has been established. This work provides an important foundation to obtain almost oxygen-free MgB2, which can finally resolve the mystery of the effect of oxygen on superconductivity in this system.

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Polarized XAFS Analyses for MgB2 Thin Films

Cited by 6 publications

References 11 publications

Enhancement in High-Field J_c Properties and the Flux Pinning Mechanism of ZnO-Buffered MgB₂ Films

Enhancement in High-Field J_c Properties and the Flux Pinning Mechanism of ZnO-Buffered MgB₂ Films

Systematic investigation into the effect of boron powder purified by different methods on the microstructures and superconductivity of MgB₂ bulks

A novel gas–solid reaction process to synthesize low oxygen MgB₂ powder using Mg vapour

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Polarized XAFS Analyses for MgB2 Thin Films

Cited by 6 publications

References 11 publications

Enhancement in High-Field Jc Properties and the Flux Pinning Mechanism of ZnO-Buffered MgB2 Films

Enhancement in High-Field Jc Properties and the Flux Pinning Mechanism of ZnO-Buffered MgB2 Films

Systematic investigation into the effect of boron powder purified by different methods on the microstructures and superconductivity of MgB2 bulks

A novel gas–solid reaction process to synthesize low oxygen MgB2 powder using Mg vapour

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Product

Resources

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Enhancement in High-Field J_c Properties and the Flux Pinning Mechanism of ZnO-Buffered MgB₂ Films

Enhancement in High-Field J_c Properties and the Flux Pinning Mechanism of ZnO-Buffered MgB₂ Films

Systematic investigation into the effect of boron powder purified by different methods on the microstructures and superconductivity of MgB₂ bulks

A novel gas–solid reaction process to synthesize low oxygen MgB₂ powder using Mg vapour