Slow electronic rearrangement kinetic involving O- after shot quenching from >600K of YBa2Cu3Oy

TL;DR

This study investigates the slow electronic rearrangements involving O- in YBa2Cu3Oy at high temperatures, revealing complex kinetic behaviors affecting structural and superconducting properties during quenching.

Contribution

It provides new insights into the electronic rearrangement kinetics involving O- in YBa2Cu3Oy above 600K, linking these to structural changes and superconductivity levels.

Findings

Electronic rearrangements involve O- with high activation energies.

Quenching from high temperatures induces significant structural and superconducting changes.

Elevated temperature superconductivity (ETS) with Tc>150K may be achievable.

Abstract

Analysis of kinetic literature suggests several electronic rearrangements above 600K involving O- (subperoxides) in YBa2Cu3Oy. Slow cooling to 260K produces a Tc=50K level with conventional plane and cell volume contracted varieties (P-V-), based on plane oxidizing (4) where (n) denotes local O coordination. When these materials are quenched from <600K, the subsequent changes at 298K of structural parameters or Tc have activation energies E=92kJ and A=1.0x10-12s. The changes saturate at temperatures where they are faster than the time constant t of quenching. This temperature is extended to 473K with SQ, indicating t=0.1s. SQ of y near 6.44 from >600K leads to increased axial ratios, plane and V expansion (P+V+), in a process which is complete near 670 and extending to 950K. P+V+ effects can far exceed P0V0 of the respective semiconductor. The relative stability at elevated temperatures indicates another intrinsically slower transformation mechanism of primarily electronic nature with E=280kJ, involving O-. V+ and its Tc=100K level, is ascribed to (3) with doped charge on apical O-, acting as a plane expander and n-doper. Similar slowing of kinetic through O- also hold for the more complex range of Tq>950K. It can produce a c-axis contracted non-superconductor (P+C-) and indications for elevated temperature superconductivity (ETS) with Tc>150K*. Kinetic data are embedded into general thermodynamic arguments concerning peroxide stability belts.