Crystals

Editorial

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2 pages, 159 KiB

Open AccessEditorial

Synthesis and Characterization of New Superconductors Materials

by Edmondo Gilioli and Davide Delmonte

Crystals 2020, 10(8), 649; https://doi.org/10.3390/cryst10080649 - 29 Jul 2020

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Abstract

In the last few decades, the persisting scientific interest in high temperature superconductor (HTS) cuprates has been accompanied by the search for new families of superconducting compounds (SPCs) [...] Full article

(This article belongs to the Special Issue Synthesis and Characterization of New Superconductors Materials)

Research

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9 pages, 7465 KiB

Open AccessArticle

The Role of Chemical Substitutions on Bi-2212 Superconductors

by Riccardo Cabassi, Davide Delmonte, Muna Mousa Abbas, Ali Razzak Abdulridha and Edmondo Gilioli

Crystals 2020, 10(6), 462; https://doi.org/10.3390/cryst10060462 - 1 Jun 2020

Cited by 13 | Viewed by 3264

Abstract

We present a study on the correlation of the superconducting critical temperature (Tc) and structural morphology with a chemically substituted high-temperature superconductor (HTS) (Bi,Pb)-2212 via Powder X-ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and [...] Read more.

We present a study on the correlation of the superconducting critical temperature (Tc) and structural morphology with a chemically substituted high-temperature superconductor (HTS) (Bi,Pb)-2212 via Powder X-ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and

d c

magnetometry. The elements Zn, Y, Ti, and Nd are incorporated within the bismuth cuprate structure at amounts that extend the ranges currently found in literature. Full article

(This article belongs to the Special Issue Synthesis and Characterization of New Superconductors Materials)

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12 pages, 809 KiB

Open AccessArticle

Two- and Three-Dimensional Superconducting Phases in the Weyl Semimetal TaP at Ambient Pressure

by Maarten R. van Delft, Sergio Pezzini, Markus König, Paul Tinnemans, Nigel E. Hussey and Steffen Wiedmann

Crystals 2020, 10(4), 288; https://doi.org/10.3390/cryst10040288 - 10 Apr 2020

Cited by 9 | Viewed by 4128 | Correction

Abstract

The motivation to search for signatures of superconductivity in Weyl semi-metals and other topological phases lies in their potential for hosting exotic phenomena such as nonzero-momentum pairing or the Majorana fermion, a viable candidate for the ultimate realization of a scalable quantum computer. [...] Read more.

The motivation to search for signatures of superconductivity in Weyl semi-metals and other topological phases lies in their potential for hosting exotic phenomena such as nonzero-momentum pairing or the Majorana fermion, a viable candidate for the ultimate realization of a scalable quantum computer. Until now, however, all known reports of superconductivity in type-I Weyl semi-metals have arisen through surface contact with a sharp tip, focused ion-beam surface treatment or the application of high pressures. Here, we demonstrate the observation of superconductivity in single crystals, even an as-grown crystal, of the Weyl semi-metal tantalum phosphide (TaP), at ambient pressure. A superconducting transition temperature,

T_{c}

, varying between 1.7 and 5.3 K, is observed in different samples, both as-grown and microscopic samples processed with focused ion beam (FIB) etching. Our data show that the superconductivity present in the as-grown crystal is inhomogeneous yet three-dimensional. For samples fabricated with FIB, we observe, in addition to the three-dimensional superconductivity, a second superconducting phase that resides on the sample surface. Through measurements of the characteristic fields as a function of temperature and angle, we are able to confirm the dimensionality of the two distinct superconducting phases. Full article

(This article belongs to the Special Issue Synthesis and Characterization of New Superconductors Materials)

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12 pages, 2774 KiB

Open AccessArticle

Comparative Study on AC Susceptibility of YBa₂Cu₃O_7−δ Added with BaZrO₃ Nanoparticles Prepared via Solid-State and Co-Precipitation Method

by Nurhidayah Mohd Hapipi, Jee Khan Lim, Soo Kien Chen, Oon Jew Lee, Abdul Halim Shaari, Mohd Mustafa Awang Kechik, Kean Pah Lim, Kar Ban Tan, Masato Murakami and Muralidhar Miryala

Crystals 2019, 9(12), 655; https://doi.org/10.3390/cryst9120655 - 9 Dec 2019

Cited by 6 | Viewed by 3335

Abstract

Polycrystalline samples of YBa₂Cu₃O_7−δ (Y-123) added with x mol% of BaZrO₃ (BZO) nanoparticles (x = 0.0, 2.0, 5.0, and 7.0) were synthesized using co-precipitation (COP) and solid-state (SS) method. X-ray diffraction (XRD) patterns showed the formation [...] Read more.

Polycrystalline samples of YBa₂Cu₃O_7−δ (Y-123) added with x mol% of BaZrO₃ (BZO) nanoparticles (x = 0.0, 2.0, 5.0, and 7.0) were synthesized using co-precipitation (COP) and solid-state (SS) method. X-ray diffraction (XRD) patterns showed the formation of Y-123 and Y-211 as the major and minor phases, respectively. The samples prepared using COP method showed higher weight percentage of Y-123 phase (≤98%) compared to the SS samples (≤93%). A peak corresponding to BZO was also found in the samples added with BZO nanoparticles. The increasing intensity of the BZO peak as the BZO amount increased showed the increasing amount of the unreacted nanoparticles in the samples. Refinement of unit cell lattice parameters indicated that all the samples have an orthorhombic crystal structure and there is no orthorhombic-tetragonal phase transformation. As observed using scanning electron microscopy (SEM), all the samples showed randomly distributed grains with irregular shape. The average grain size for the pure sample prepared using COP method is smaller (0.30 µm) compared with that of the pure SS sample (1.24 µm). Addition of 7.0 mol% BZO led to an increase of average grain size to 0.50 μm and 2.71 μm for the COP and SS samples, respectively, indicating grain growth. AC susceptibility (ACS) measurement showed a decrease in the onset critical temperature, T_c-onset with BZO addition. Comparatively, T_c-onset for the COP samples is higher than that of the SS samples. The value of Josephson’s current, I_o increased up to 2.0 mol% BZO addition, above which the I_o decreased more drastically for the SS samples. The value of I_o is 53.95 μA and 32.08 μA for the 2.0 mol% BZO added SS and COP samples, respectively. The decrease of I_o is attributed to the distribution of BZO particles at the grain boundaries as also reflected in the drastic decrease of phase lock-in temperature, T_cj. As a result of smaller average grain size, the presence of more grain boundaries containing insulating BZO particles led to lower I_o in the COP samples. Full article

(This article belongs to the Special Issue Synthesis and Characterization of New Superconductors Materials)

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9 pages, 1951 KiB

Open AccessArticle

Synthesis of ErBa₂Cu₃O_7−δ Superconductor Solder for the Fabrication of Superconducting Joint between Gdba₂cu₃o_7−δ Coated Conductor

by Zili Zhang, Lei Wang, Jianhua Liu and Qiuliang Wang

Crystals 2019, 9(10), 492; https://doi.org/10.3390/cryst9100492 - 25 Sep 2019

Cited by 5 | Viewed by 2765

Abstract

ErBa₂Cu₃O_7−δ (Er123) superconductor is one of the best candidates of superconductor solder for the fabrication of superconducting joint between GdBa₂Cu₃O_7−δ (Gd123) coated conductor, due to its high T_c value (93 K) and [...] Read more.

ErBa₂Cu₃O_7−δ (Er123) superconductor is one of the best candidates of superconductor solder for the fabrication of superconducting joint between GdBa₂Cu₃O_7−δ (Gd123) coated conductor, due to its high T_c value (93 K) and highest optimized oxygen annealing temperature among RE123 compounds. In this paper, we systematically research the effect of sintering parameters on the phase formation, microstructure and superconducting properties of Er123 powder. The optimized synthesis route to acquire high purity Er123 powder with as good superconducting properties as Gd123 has been uncovered. The melt temperature of Er123 with different dopant compared to Gd123 is also investigated, and the feasible operating temperature range of Er123 superconductor solder is discussed. This work reveals a very important starting point on fabrication high-quality superconducting joint between the commercial Gd123 coated conductor, which can further improve the development of the persistent operating mode on ultra-high field nuclear magnetic resonance and magnetic resonance imaging. Full article

(This article belongs to the Special Issue Synthesis and Characterization of New Superconductors Materials)

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11 pages, 537 KiB

Open AccessArticle

Field-Angle Dependence of Interlayer Magnetoresistance in Organic Dirac Electron System α-(BEDT-TTF)₂I₃

by Takehiro Tani, Naoya Tajima and Akito Kobayashi

Crystals 2019, 9(4), 212; https://doi.org/10.3390/cryst9040212 - 19 Apr 2019

Cited by 6 | Viewed by 2845

Abstract

The effect of the Coulomb interaction in interlayer magnetoresistance is elucidated in collaboration with theory and experiments for the Dirac electron system in organic conductor

α

-(BEDT-TTF)

_{2}

I

_{3}

under a strong magnetic field. It is found that the effective g-factor [...] Read more.

The effect of the Coulomb interaction in interlayer magnetoresistance is elucidated in collaboration with theory and experiments for the Dirac electron system in organic conductor

α

-(BEDT-TTF)

_{2}

I

_{3}

under a strong magnetic field. It is found that the effective g-factor enhanced by Coulomb interaction depends on the angle of the magnetic field, resulting in the field-angle dependence of a characteristic magnetic field in which interlayer resistance has a minimum due to spin splitting

N = 0

Landau levels. The qualitative agreement between the theory and experimental results for the field-angle dependence of interlayer magnetoresistance is obtained. Full article

(This article belongs to the Special Issue Synthesis and Characterization of New Superconductors Materials)

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Review

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21 pages, 12221 KiB

Open AccessReview

Highly-Tunable Crystal Structure and Physical Properties in FeSe-Based Superconductors

by Kaiyao Zhou, Junjie Wang, Yanpeng Song, Liwei Guo and Jian-gang Guo

Crystals 2019, 9(11), 560; https://doi.org/10.3390/cryst9110560 - 25 Oct 2019

Cited by 6 | Viewed by 5060

Abstract

Here, crystal structure, electronic structure, chemical substitution, pressure-dependent superconductivity, and thickness-dependent properties in FeSe-based superconductors are systemically reviewed. First, the superconductivity versus chemical substitution is reviewed, where the doping at Fe or Se sites induces different effects on the superconducting critical temperature ( [...] Read more.

Here, crystal structure, electronic structure, chemical substitution, pressure-dependent superconductivity, and thickness-dependent properties in FeSe-based superconductors are systemically reviewed. First, the superconductivity versus chemical substitution is reviewed, where the doping at Fe or Se sites induces different effects on the superconducting critical temperature (T_c). Meanwhile, the application of high pressure is extremely effective in enhancing T_c and simultaneously induces magnetism. Second, the intercalated-FeSe superconductors exhibit higher T_c from 30 to 46 K. Such an enhancement is mainly caused by the charge transfer from the intercalated organic and inorganic layer. Finally, the highest T_c emerging in single-unit-cell FeSe on the SrTiO₃ substrate is discussed, where electron-phonon coupling between FeSe and the substrate could enhance T_c to as high as 65 K or 100 K. The step-wise increment of T_c indicates that the synergic effect of carrier doping and electron-phonon coupling plays a critical role in tuning the electronic structure and superconductivity in FeSe-based superconductors. Full article

(This article belongs to the Special Issue Synthesis and Characterization of New Superconductors Materials)

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