Journal of Superconductivity and Novel Magnetism https://doi.org/10.1007/s10948-019-5106-4 ORIGINAL PAPER Transmission EBSD (t-EBSD) as Tool to Investigate Nanostructures in Superconductors A. Koblischka-Veneva 1,2 · M. R. Koblischka 1,2 · J. Schmauch 1 · M. Murakami 2 Received: 31 March 2019 / Accepted: 8 April 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract The transmission electron backscatter diffraction (t-EBSD) technique has proven to be an indispensable tool for the analysis of microstructures of superconducting samples, both high-T c samples (YBa 2 Cu 3 O y , Bi 2 Sr 2 CaCu 2 O 8 ) as well as MgB 2 or iron-based materials. The knowledge of the grain boundary properties (misorientation, length, width) is essential for the further optimization of sample performance. Any addition of secondary phase(s) to improve the flux pinning properties is required to be of nanometer dimensions, so the higher achievable resolution and the better imaging properties are important to obtain reasonably high image quality to enable automated orientation mapping. The orientation maps reveal not only the location and the shape of the inclusions within the superconducting matrix or at the grain boundaries but also their influence on the surrounding superconducting matrix, which also plays an important role in flux pinning. In the case of sintered MgB 2 bulk samples, the demand for higher critical current densities leads to MgB 2 grains in the 100-nm range, which is already difficult to be studied by means of conventional EBSD. Furthermore, t-EBSD is useful for the analysis of specific microstructures of unconventional superconductors like superconducting foams or superconducting nanowire networks. Keywords Superconductors · Transmission electron backscatter diffraction · Nanometer-sized grains · Pinning centers · Orientation mapping 1 Introduction A proper knowledge of the microstructure of supercon- ducting samples is essential for the interpretation of data obtained from integral measurement techniques like mag- netization, AC susceptibility, or electric transport data. For this purpose, the electron backscatter diffraction (EBSD) tech- nique has proven to be a very useful tool on metallic and as well on ceramic samples [1–4]. In the case of YBa 2 Cu 3 O y (YBCO) superconductors, the introduction of flux pinning sites in the nanometer range demands a high-resolution  M. R. Koblischka miko@shibaura-it.ac.jp; m.koblischka@gmail.com A. Koblischka-Veneva anjela@shibaura-it.ac.jp 1 Experimental Physics, Saarland University, P.O.Box 151150, 66041 Saarbr¨ ucken, Germany 2 Superconducting Materials Laboratory, Department of Materials Science and Engineering, Shibaura Institute of Technology, Tokyo 135-8548, Japan microstructure analysis, whereas polycrystalline materials like MgB 2 or iron-based superconductors show grain sizes in the nanometer range, which is also difficult to be analyzed for conventional analysis methods. The transmission EBSD (t-EBSD) technique was very recently developed by several authors in the literature [5–7] with the goal to obtain higher spatial resolution of the EBSD technique on materials with nanometer-sized grains. As result of these efforts, the spatial resolution was improved from several tens of nanometers to ∼ 5–10 nm, depending on the material to be studied [8, 9]. Furthermore, the charging effects due to the electron flow in non-conducting samples are considerably reduced, which is a great advantage for ceramic materials or even biomaterials [10]. All these improvements make t-EBSD the method of choice to analyze the crystallographic orientations and grain boundary misorientations also in superconducting materials. Up to now, the use of t-EBSD was concentrated mainly on MgB 2 , where the nanometer-sized grains and carbon addi- tions as flux pinning sites play an important role [11, 12]. In the case of sintered, polycrystalline MgB 2 samples prepared using various reaction temperatures, the t-EBSD technique was found to be the only way to obtain EBSD mappings on all the samples [12], and the crystallographic orientations