title: Nanoscale Stoichiometric Analysis of a High-Temperature Superconductor by Atom Probe Tomography.
abstract: The functional properties of the high-temperature superconductor Y1Ba2Cu3O7-δ (Y-123) are closely correlated to the exact stoichiometry and oxygen content. Exceeding the critical value of 1 oxygen vacancy for every five unit cells (δ>0.2, which translates to a 1.5 at% deviation from the nominal oxygen stoichiometry of Y7.7Ba15.3Cu23O54-δ ) is sufficient to alter the superconducting properties. Stoichiometry at the nanometer scale, particularly of oxygen and other lighter elements, is extremely difficult to quantify in complex functional ceramics by most currently available analytical techniques. The present study is an analysis and optimization of the experimental conditions required to quantify the local nanoscale stoichiometry of single crystal yttrium barium copper oxide (YBCO) samples in three dimensions by atom probe tomography (APT). APT analysis required systematic exploration of a wide range of data acquisition and processing conditions to calibrate the measurements. Laser pulse energy, ion identification, and the choice of range widths were all found to influence composition measurements. The final composition obtained from melt-grown crystals with optimized superconducting properties was Y7.9Ba10.4Cu24.4O57.2.
authors.affiliation: 1Department of Materials,University of Oxford,Parks Road, ,Oxford OX1 3PH,UK.
authors.forename: Stella
authors.initials: S
authors.lastname: Pedrazzini
authors.affiliation: 1Department of Materials,University of Oxford,Parks Road, ,Oxford OX1 3PH,UK.
authors.forename: Andrew J
authors.identifier: 0000-0001-6959-9849
authors.initials: AJ
authors.lastname: London
authors.affiliation: 1Department of Materials,University of Oxford,Parks Road, ,Oxford OX1 3PH,UK.
authors.forename: Baptiste
authors.identifier: 0000-0002-4934-0458
authors.initials: B
authors.lastname: Gault
authors.affiliation: 3Geoscience Atom Probe, Advanced Resource Characterisation Facility,John de Laeter Centre,Curtin University,Perth,WA 6102,Australia.
authors.forename: David
authors.initials: D
authors.lastname: Saxey
authors.affiliation: 1Department of Materials,University of Oxford,Parks Road, ,Oxford OX1 3PH,UK.
authors.forename: Susannah
authors.initials: S
authors.lastname: Speller
authors.affiliation: 1Department of Materials,University of Oxford,Parks Road, ,Oxford OX1 3PH,UK.
authors.forename: Chris R M
authors.initials: CRM
authors.lastname: Grovenor
authors.affiliation: 1Department of Materials,University of Oxford,Parks Road, ,Oxford OX1 3PH,UK.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Danaie
authors.affiliation: 1Department of Materials,University of Oxford,Parks Road, ,Oxford OX1 3PH,UK.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Moody
authors.affiliation: 4Oak Ridge National Laboratory,Materials Science & Technology Division,1 Bethel Valley Road,Oak Ridge,TN 37831,USA.
authors.forename: Philip D
authors.initials: PD
authors.lastname: Edmondson
authors.affiliation: 1Department of Materials,University of Oxford,Parks Road, ,Oxford OX1 3PH,UK.
authors.forename: Paul A J
authors.initials: PAJ
authors.lastname: Bagot
keywords: Atom probe tomography; YBCO; stoichiometry; superconductor