title: Scanning SQUID microscopy of local superconductivity in inhomogeneous combinatorial ceramics.
abstract: Although combinatorial solid-state chemistry promises to be an efficient way to search for new superconducting compounds, the problem of determining which compositions are strongly diamagnetic in a mixed-phase sample is challenging. By means of reactions in a system of randomly mixed starting components (Ca, Sr, Ba, La, Y, Pb, Bi, Tl, and Cu oxides), samples were produced that showed an onset of diamagnetic response above 115 K in bulk measurements. Imaging of this diamagnetic response in ceramic samples by scanning SQUID microscopy (SSM) revealed local superconducting areas with sizes down to as small as the spatial resolution of a few micrometers. In addition, locally formed superconducting matter was extracted from mixed-phase samples by magnetic separation. The analysis of single grains (d<80 μm) by X-ray diffraction, elemental analysis, and bulk SQUID measurements allowed Tl2Ca3Ba2Cu4O12, TlCaBaSrCu2O(7-δ), BaPb(0.5)Bi(0.25)Tl(0.25)O(3-δ), TlBa2Ca2Cu3O9, Tl2Ba2CaCu2O8, and YBa2Cu3O7 phases to be identified. SSM, in combination with other diagnostic techniques, is therefore shown to be a useful instrument to analyze inhomogeneous reaction products in the solid-state chemistry of materials showing magnetic properties.
authors.affiliation: Department of Chemistry and Biochemistry, Berne University, Freiestrasse 3, 3012 Bern (Switzerland), Fax: (+41) 31-631-42-72.
authors.forename: Mitra
authors.initials: M
authors.lastname: Iranmanesh
authors.forename: Manuela
authors.initials: M
authors.lastname: Stir
authors.forename: John R
authors.initials: JR
authors.lastname: Kirtley
authors.forename: Jürg
authors.initials: J
authors.lastname: Hulliger
keywords: ceramics; combinatorial chemistry; magnetic properties; scanning probe microscopy; superconductors