Single Crystal Growth of Cuprate Superconductor (Lu_0.8Nd_0.2)Ba₂Cu₄O₈ by KOH Flux Method

Abstract

Single crystals of Nd-substituted LuBa2Cu4O8 were successfully grown by the KOH flux method. The single phase of Lu1-xNdxBa2Cu4O8 [(Lu,Nd)124] formed at x = 0.2. The compound crystallized as orthorhombic Ammm structure with lattice constants of a = 3.835(3) Å, b = 3.879(2) Å and c = 27.195(6) Å. Single crystal structural analysis demonstrated that the Nd ion partially occupied the Lu site. The (Lu,Nd)124 exhibited the superconducting transition at ~75 K in the magnetic susceptibility and resistivity. The Tc and the c-axis of the (Lu,Nd)124 corresponded to Tm124. These results indicate that RE124 equivalent to the one composed of single RE element is obtained by combination of two RE elements.

New Compounds and Phase Selection of Nickel Sulfides via Oxidation State Control in Molten Hydroxides

“…High-temperature fluxes are a great tool for material synthesis because they offer moderate temperature regimes, crystal growth, and kinetic stabilization of compounds that cannot be prepared by direct high-temperature synthesis. − Reactions conducted in fluxes have been exploited to discover materials, such as complex metal oxides, chalcogenides, and pnictides. These materials exhibit diverse properties, such as large optical nonlinearities, ion-exchange, high critical temperature ( T c ) superconductivity, high-performance thermoelectricity, and photovoltaic conversion. − However, like most solid-state syntheses, the “black-box” nature of high-temperature fluxes offers little or no insight into solvated species, reaction mechanisms, intermediates, or nucleation. Thus, without adequate knowledge of these reaction processes, compound design for extended solids that begins at the molecular level lags behind organic synthesis, in which molecules can be planned step-by-step on a drawing board via retrosynthesis.…”

Fabrication of a superconducting YBa2Cu4O8 film via coprecipitation

“…[23][24][25][26][27][28] Near the surface of our Y-124 film was Y-poor composition suggested by EDX analysis, however, the temperature dependence was typical of in-plane characteristics of an as-grown RE-124 single crystal. 28,29) Thus, we considered that the resistance in normal state was originated from the bulk properties of the synthesized Y-124 film. Our new method can produce the c-axis oriented and nearly single phase Y124 films by just dipping the precipitations on a substrate and heating.…”

“…In the normal state (80 K < T < 300 K), the resistance showed a metallic and upper-curvature shape coming from the nature of the under-doped cuprate superconductor. [30][31][32][33][34][35][36] It is assumed that such behavior appears universally in cuprates, [30][31][32][33][34][35][36] due to the in-plane scattering rate of the electrons being reduced by the pseudogap opening. [30][31][32][33][34][35] Near the surface of our Y-124 film was the Y-poor composition suggested by EDX analysis, however, the temperature dependence of resistance was a metallic and upper-curvature shape as well as an as-grown RE-124 bulk single crystal.…”

“…[30][31][32][33][34][35] Near the surface of our Y-124 film was the Y-poor composition suggested by EDX analysis, however, the temperature dependence of resistance was a metallic and upper-curvature shape as well as an as-grown RE-124 bulk single crystal. 35,36) Thus, we considered that the resistance in the normal state originated from the bulk properties of the synthesized Y-124 film.…”