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| Home > Publications database > Studies of atomic scale diffusion by x-ray photon correlation spectroscopy |
| Poster | DESY-2014-01373 |
; ; ;
2013
Abstract: Although Quasielastic Neutron Scattering (QNS) has proven successful in investigating diffusive dy-namics at the atomic level in solid state physics, the limits for the diffusion coefficient are relativelylow. Therefore QNS is in general limited to measurements in the vicinity of the melting transition.Also, because of the specific scattering cross section of neutrons, it favors selected atoms like hydro-gen or lithium. The goal of our studies in the last years was to overcome these limitations by using anew method to study atomic motion at the fundamental level. This method should ideally work in abroad spectrum of solids and enlarge the accessible range of temperatures.Our group managed to develop the relatively new technique of X-ray photon correlation to work on theatomic scale. This technique operates in the time regime rather than in the energy regime and measureschemical fluctuations instead of self diffusion. Atomic scale X-ray photon correlation spectroscopy(aXPCS) is therefore not subject to the limitations mentioned above. The time resolution towards fasterdynamics is only limited by the readout time of the detector and intensity of the X-ray beam. Towardsslower dynamics it is limited by the stability and the duration of the experiment. Even though at the mo-ment a high contrast in the scattering length of the system under investigation is required due to today’stechnical limitations at synchrotron sources, there is practically no restriction to certain elements forthis technique. aXPCS therefore allows to investigate atomic scale diffusion in the temperature rangeof intermetallic phases or to study dynamics of glasses well below glass transition temperatures.10−21T (K)84086082010−1510−19−23100.710−2210−230.91.1scpc1.161.181.201.221.241/T (10−3 K−1)Figure 1: Diffusivities of Ni-Pt solid solution measured with aXPCS at the ESRF for single crystal (sc) andpolycrystalline sample (pc) compared with tracer data (circles) [3]. (This data was published in [2].)The first successful aXPCS experiment was carried out only a few years ago by our group [1]. Thisposter will give an overview of an experimental setup and show what we have been able to experimen-tally achieve since then. The systems presented will be a Ni-Pt solid solution with jump frequencies inthe order of τ −1 ∼ 10−3 s−1 (see Figure 1) [2] and an Fe-Al intermetallic alloy.This work was supported by the Austrian Science Fund (FWF): P22402.
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