Speaker
Description
Single crystals often present disorder in their structure due to dopant substitution/intercalation or as an intrinsic instability of the compound. In many cases the disorder-to-order balance is responsible for key properties of the material. For example it can account for low thermal conductivity in PbTe or for the superconducting transition temperature in Sr2RuO4 where the highest Tc is obtained in disorder-free samples.
Here we present the three-dimensional mapping technique of diffuse scattering. At the Broad-Band Diffraction Swedish Material Science beamline (P21.1) at PETRA III synchrotron radiation source, total scattering measurements are possible thanks to the combination of high energy x-rays (100 keV) and large area detectors. Diffraction signal is acquired at high repetition rate allowing to operate with high incident photon flux. This is essential since the signal contains both the high intensity Bragg reflections, related to the average crystal structure, and the low intensity diffuse scattering signal accounting for the disorder. The acquired data are reconstructed in the hkl space and can be converted into the real space by Fourier transformation obtaining the three dimensional pair distribution function (3D-PDF) [1-3]. This technique is presented with the results obtained on perfect Si crystal as a standard. It is shown that 3D-PDF is sensitive to minor imperfections and/or impurities in the material.
[1] P. Schaub, T. Weber and W. Steurer, Philosophical Magazine 87, 2781–2787 (2007)
[2] T. Weber and A. Simonov, Z. Kristallogr. 227, 238–247 (2012)
[3] N. Roth et al., IUCrJ 5, 410–416 (2018)
