Remote access to electrical conductivity in ion conducting solids by means of charge carrier attachment from a fs-laser plasma

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The electrical conductivity of ion conducting solid materials will be studied by means of the charge attachment induced transport (CAIT) technique, based on charge carriers from a fs-laser generated plasma. The underlying working principles has been proven in preliminary work. The approach shall be established, further advanced and applied to state-of-the-art scientific questions. The fs-laser ionization allows formation of a diversity of chemical charge carriers, e.g. oxygen anions and cations, protons, electrons, rare gas cations etc. at adjustable pressure and temperature under conditions which constitute a plasma. Attachment of polarity selected charge carriers from the plasma to a solid sample leads to the generation of well-defined gradients of the electrochemical potential, which in turn induces charge carrier transport in the sample. Transport coefficients can be either derived from current-voltage measurements or from the analysis of concentration depth profiles. The unique selling point of the approach is that a large variety of charge carriers can be attached to a sample under soft conditions and only triggers the actual electro-diffusive transport. In contrast to most established techniques, the Plasma-CAIT operates with only one contact between the sample and a metal electrode, at which the current will be measured. The plasma constitutes a virtual electrode with well-defined electro-chemical potential. Blocking zones can be rigorously avoided by this approach. The approach constitutes a remote access to electrical conductivity under conditions of DC-transport as relevant for all battery and fuel cell applications. One goal of the project is the development of a measuring routine for absolute conductivities circumventing the need for separate calibration measurements. In total measurement are planned to cover a range from mbar to several bar, with an emphasis on ambient conditions. Temperatures and eventually relative humidity will also be controlled. The Plasma-CAIT technique will be further developed for the example of Lithium-Aluminum-Germanium-Phosphate (LAGP) an important ion conductor and subsequently applied to a typical high temperature fuel cell material, i.e. yttrium stabilized zirconia (YSZ). The additional scientific knowledge gained by these studies pertains to the unambiguous identification of native charge carriers and the determination of element-specific transport coefficients, including partial transport coefficients for oxygen ions, lithium ions and protons in ion conducting solids.