A simple statistical phenomenological model for cation substitutions in Nd1+xBa2−xCu3O7−δ+x/2

Gombos, M.; Varesi, E.; Tedesco, P.; Vecchione, A.; Pace, S.

doi:10.1080/14786430802178079

Cited by 4 publications

(1 citation statement)

References 14 publications

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“…We can then wonder if the preferential a and b axis orientation observed in Nd123 may be correlated to this feature. It is known that Nd123 admits a wide range of solid solutions Nd123(x) (= Nd 1+x Ba 2−x Cu 3 O z ) where Ba 2+ is partially substituted by Nd 3+ [18][19][20][21]36]. The disordering of Nd and Ba antisites in Nd123(x) depresses the superconductivity and also has important repercussions on its crystallographic structure [37].…”

Section: Discussionmentioning

confidence: 99%

Reduced twinning efficiency and tri-dimensional crack structure in melt-textured NdBa₂Cu₃O_7−δbulk samples fragmentation process

Gombos

Gomis

Ciancio

et al. 2012

Supercond. Sci. Technol.

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Here we report on a detailed investigation on NdBa 2 Cu 3 O 7−δ (Nd123) crack generation achieved by an extensive morphological and structural study on 1 cm diameter top-seeded melt-textured grown pellets, where crack development stops at an earlier stage, and on the parallelepiped fragments resulting from the spontaneous breaking of larger (3 and 5 cm diameter) pellets. In this way complementary information on the process is obtained.Sample morphology was investigated by polarized light optical microscopy, scanning electron microscopy, and atomic force microscopy, confirming that microscopic fissures and macroscopic cracks act as preferential oxygenating channels. This fact suggests that mechanical stress, generated locally by an oxygenation induced tetragonal-orthorhombic transition, is the driving mechanism for fissure evolution into cracks and their further growth. Our observations reveal that Nd123 fissure bundles have a tri-dimensional character, lying not only along the a-b plane, but also along two a-b out-of-plane perpendicular directions. Twin and fissure bundle orientations appear to differ by 45 • , thus suggesting that fissures lie along a-c and/or b-c crystallographic planes.This observation was confirmed by θ -2θ x-ray diffraction and x-ray pole figure analysis (XPFA) performed on the parallelepiped fragments, which revealed that samples are single domain, with edges oriented along the principal crystallographic planes. XPFA detected a-b axes twinning in the domain on the global scale.A remarkable result achieved by electron backscattered diffraction (EBSD) is the evidence that cracking along b-c plane is preferred with respect to a-c, acting in this way as a second preferential cleavage direction. Indeed EBSD measurements show long-range ordering of a and b axes, suggesting that twinning is less effective in releasing in-plane mechanical stress in Nd123 than in parent compounds. Results are discussed on the basis of the identification of Nd-Ba cationic substitutions as the main competing relaxation mechanism.The superconducting properties of the analysed samples were studied by measuring the fragments superconducting parameters by vibrating sample magnetometry.

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Section: Discussionmentioning

confidence: 99%

Reduced twinning efficiency and tri-dimensional crack structure in melt-textured NdBa₂Cu₃O_7−δbulk samples fragmentation process

Gombos

Gomis

Ciancio

et al. 2012

Supercond. Sci. Technol.

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High Tc superconductors for plasmonics and metamaterials fabrication: A preliminary normal state optical characterisation of Nd123 and Gd1212

Gombos

Romano

Rendina

et al. 2013

Journal of Applied Physics

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The application of metamaterials and plasmonic structures in the visible and near infrared are strongly limited by the dissipative losses due to the low conductivity of the most used metals in this frequency range. High temperature superconductors are plasmonic materials at nonzero temperature that can provide a possible alternative approach to overcome this limit. Moreover, they can have zero or even negative dielectric constant, and a bipolar behavior. All these characteristics are attractive for plasmonic applications, and encourage further studies aimed at a more detailed knowledge of the parameters characterizing high temperature superconductors as possible optical materials. In this paper, Fourier Transform Infrared Spectroscopy analysis and ellipsometric measurements in the visible and infrared spectral regions on NdBa2Cu3O7−δ (Nd123) and ruthenocuprate superconductor GdSr2RuCu2O8−δ (Gd1212) are reported. As a matter of fact, Nd123 presents the highest transition temperature (Tc = 96 K) and the most interesting magnetic response properties among YBCO-like cuprate superconductors, whereas the coexistence in the same cell of superconductivity and magnetic order below Tc in Gd1212 can be an interesting feature for next metamaterial-like applications. The obtained results confirm the promising features of the considered materials.

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Normal-State Optical Features Study of Nd123 and Gd1212 HTSC Materials for Photonics and Metamaterials Fabrication

Managò

DeLuca

Rendina

et al. 2016

IEEE Trans. Appl. Supercond.

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YBCO-like Nd123 and Gd1212 superconductors in the normal state, in the visible and infrared regime, have been analyzed in this work. Superconductors, particularly high-temperature superconductors (HTSCs), hold indeed a great interest in the highly innovative research field of metamaterials and photonics with important applications. Indeed nanostructured devices suffer from increasing resistivity with frequency in metals, and superconducting materials provide a viable route to approach this problem. Moreover, HTSCs are plasmonic materials at nonzero temperature, and their features, not available in conventional materials, make them very attractive for metamaterials use. In particular, we investigate Nd123, for its high Tc, and Gd1212, for the coexistence, in its unitary cell, of magnetic order and superconductivity. Samples were extracted from top-seeded melt-textured growth bulk pellets and bars. Fourier transform infrared spectroscopy analysis, performed in the far-infrared, shows articulated peak structures with k < kmin and a plateau for higher k, allowing for Nd123 and Gd1212 pseudogap measurement. Raman spectroscopy and microscopy provided a structural mapping of our Nd123 samples, allowing for distinguishing the superconducting matrix from nonsuperconducting phase inclusions (precipitates) and providing an instrument to discriminate among optical responses of the different compounds

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A simple statistical phenomenological model for cation substitutions in Nd₁₊_xBa₂₋_xCu₃O_7−δ+_x_/2

Cited by 4 publications

References 14 publications

Reduced twinning efficiency and tri-dimensional crack structure in melt-textured NdBa₂Cu₃O_7−δbulk samples fragmentation process

Reduced twinning efficiency and tri-dimensional crack structure in melt-textured NdBa₂Cu₃O_7−δbulk samples fragmentation process

High Tc superconductors for plasmonics and metamaterials fabrication: A preliminary normal state optical characterisation of Nd123 and Gd1212

Normal-State Optical Features Study of Nd123 and Gd1212 HTSC Materials for Photonics and Metamaterials Fabrication

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A simple statistical phenomenological model for cation substitutions in Nd1+xBa2−xCu3O7−δ+x/2

Cited by 4 publications

References 14 publications

Reduced twinning efficiency and tri-dimensional crack structure in melt-textured NdBa2Cu3O7−δbulk samples fragmentation process

Reduced twinning efficiency and tri-dimensional crack structure in melt-textured NdBa2Cu3O7−δbulk samples fragmentation process

High Tc superconductors for plasmonics and metamaterials fabrication: A preliminary normal state optical characterisation of Nd123 and Gd1212

Normal-State Optical Features Study of Nd123 and Gd1212 HTSC Materials for Photonics and Metamaterials Fabrication

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A simple statistical phenomenological model for cation substitutions in Nd₁₊_xBa₂₋_xCu₃O_7−δ+_x_/2

Reduced twinning efficiency and tri-dimensional crack structure in melt-textured NdBa₂Cu₃O_7−δbulk samples fragmentation process

Reduced twinning efficiency and tri-dimensional crack structure in melt-textured NdBa₂Cu₃O_7−δbulk samples fragmentation process