Pedrazzini Stella, London Andrew J, Gault Baptiste, Saxey David, Speller Susannah, Grovenor Chris R M, Danaie Mohsen, Moody Michael P, Edmondson Philip D, Bagot Paul A J
1Department of Materials,University of Oxford,Parks Road, ,Oxford OX1 3PH,UK.
3Geoscience Atom Probe, Advanced Resource Characterisation Facility,John de Laeter Centre,Curtin University,Perth,WA 6102,Australia.
Microsc Microanal. 2017 Apr;23(2):414-424. doi: 10.1017/S1431927616012757. Epub 2017 Jan 31.
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.
高温超导体Y1Ba2Cu3O7-δ（Y-123）的功能特性与精确的化学计量比和氧含量密切相关。每五个晶胞中氧空位超过临界值1（δ>0.2，这相当于偏离Y7.7Ba15.3Cu23O54-δ的名义氧化学计量比1.5原子百分比）就足以改变超导特性。在纳米尺度上的化学计量比，尤其是氧和其他较轻元素的化学计量比，用目前大多数可用的分析技术在复杂功能陶瓷中极难量化。本研究是对通过原子探针断层扫描（APT）在三维空间中量化单晶钇钡铜氧化物（YBCO）样品局部纳米尺度化学计量比所需实验条件的分析和优化。APT分析需要系统地探索广泛的数据采集和处理条件以校准测量。发现激光脉冲能量、离子识别和范围宽度的选择都会影响成分测量。从具有优化超导特性的熔体生长晶体获得的最终成分是Y7.9Ba10.4Cu24.4O57.2。
