Istituto di Cristallografia - CNR

Tensile Microstrain Fluctuations in the BaPbO Units in Superconducting BaPb1-xBixO3 by Scanning Dispersive Micro-XANES

BaPb1-xBixO3 (BPBO) bismuthate, showing high TC superconductivity for 0.05 < x < 0.35, is an archetypal system for studying the complex inhomogeneity of perovskite lattice favoring the emergence of quantum coherence, called the superstripes phase. Local lattice fluctuations, detected by EXAFS; nanoscale stripes, detected by electron microscopy; and two competing crystalline structures, detected by diffraction, are known to characterize the superconducting phase. At nanoscale [BaBiO3] centered nanoscale units (BBO) coexist with BaPbO3 centered (BPO) units in the BPBO perovskite; therefore, we expect a tensile microstrain in BPO units due the misfit strain between the two different lattices. Here, we report the measurement of the spatial micro-fluctuations of the local tensile microstrain ? in the BaPO units in superconducting Ba(Pb1-xBix)O3 crystals with x1 = 0.19 an x2 = 0.28. We show here the feasibility of applying the scanning dispersive micro-X-ray absorption near edge structure (Sd?XANES) technique, using focused synchrotron radiation, to probe the microscale spatial fluctuations of the microstrain in BPO units. This unconventional real-space Sd?XANES microscopy at the Pb L3 edge has been collected in the dispersive mode. Our experimental method allows us to measure either the local Bi chemical concentration x and the local lattice microstrain of local BBO and BPO units. The 5 ? 5 micron-size spots from the focused X-ray beam allowed us to obtain maps of 1600 points covering an area of 200 ? 200 microns. The mapping shows a substantial difference between the spatial fluctuations of the microstrain ? and the chemical inhomogeneity x. Moreover, we show the different relations ?(x) in samples with lower (x1 = 0.19) and higher (x2 = 0.28) doping respect to the optimum doping (x = 0.25). ? 2023 by the authors.

Condensed matter
Impact factor
Albertini, Ruben and Macis, Salvatore and Ivanov, Andrei A. and Menushenkov, Alexey P. and Puri, Alessandro and Monteseguro, Virginia and Joseph, Boby and Xu, Wei and Marcelli, Augusto and Giraldo-Gallo, Paula and Fisher, Ian Randal and Bianconi, Antonio and Campi, Gaetano
Autori IC CNR