Influence of precursor oxygen stoichiometry on the formation of Hg, Re-1223 superconductors

Abstract

Thanks to a novel technique (thermobaric analyser or TBA) for measuring the in situ pressure in quartz tubes, we have investigated the precursor quality for the synthesis of the superconductor Hg-1223 which is an essential parameter to control. We have made this study on the samples and we can conclude that this superconductor phase requires a ceramic precursor sintered in a low mixture gas flux. An excessively oxygenated precursor leads to overdoped superconducting phases, presence of other members with lower n, and some unreacted precursor. The precursor oxygenation degree also modifies the kinetics of formation of and the partial melting of the superconductor material may be affected.

Critical Current Model for Polycrystalline Compounds with an Intrinsic Solid Solution of Two Mixed Superconductor Phases

“…The pinning energy can be related to the morphology and grain boundary composition in the intergrain region when a low magnetic field is applied for T ≈ T c [31].…”

The Influence of Oxygen Partial Pressure on Growth of the (Hg,Re)-1223 Intergrain Junction

“…First, the preparation of the ceramic precursor typical began with a mixture of Ba Ca Cu O (99.0% PRAXAIR) and ReO (99.0% Aldrich) in powder form with the molar relationship 1 : 0.18 [15]. These powders were homogenised in an agate mortar and pelletised with an uniaxial pressure of 0.5 GPa.…”

“…Specifically, the samples with 18% nominal atomic Re have presented an improvement of the superconducting properties, [10] such as the critical current density [12], as compared with that of the pure Hg-1223 sample. The influence of the oxygen partial pressure on the bulk properties for Hg Re Ba Ca Cu O Hg,Re polycrystalline samples has been reported in [13]- [15]. In spite of the different oxygen partial pressure of the precursor, a doubt can arise about whether these Hg-based cuprates actually present distinct oxygen doping levels.…”

Structural and Superconducting Properties of Hg0.75Re0.25Ba2−xSrxCa2Cu3O8+δ Superconductors Grown by Sol–Gel and Sealed Quartz Tube Synthesis

“…This could mean that the overdoping is obtained under the thermal treatment conditions applied in the synthesis process. In a previous work it was demonstrated that the "nal oxygen content of the (Hg,Re)-1223 as-prepared superconducting samples (39,46) can be de"ned during the precursor synthesis.…”