guest ::
| Home > Publications database > Effect of (External) Electric Fields on The Heterogeneous Solid State Reaction between Al2O3 and Y2O3 Forming Multiple Product Layers |
| Home > Publications database > Effect of (External) Electric Fields on The Heterogeneous Solid State Reaction between Al2O3 and Y2O3 Forming Multiple Product Layers |
| Abstract | FZJ-2024-00951 |
;
2023
Abstract: Ceramics materials are used in many technologically important applications, e.g. electronics, sensors, energy conversion and storage. Solid state reactions as degradation process play an important role at elevated temperatures, especially in the case of short diffusion length (miniaturisation) or if an extended lifetime is required. This includes redox reactions and reactions only due to the transport of ions, resulting in the (heterogeneous) formation of product phases. Under working conditions, devices are not only subjected to elevated temperatures but also to electric fields, acting as a second driving force on the mobile charge carriers in addition to chemical potential gradients. Beyond, the importance for degradation processes, the influence of electric fields on solid state reactions gains also more importance for the preparation of ceramic materials. In the last years the field-assisted (flash) sintering (FAST) and the spark plasma sintering (SPS) techniques were developed to a mature state.In this experimental study the influence of an electric field on the kinetics and morphological evolution on the heterogeneous solid state reaction between Al2O3 and Y2O3 is highlighted. The reaction couples were prepared in thin film technique by pulsed laser deposition (PLD). Depending on the reaction temperature, up to three product layers (garnet: YAG, perovskite: YAP and a monoclinic phase: YAM) can be formed. The kinetic parameters for the only thermally activated reactions were determined. [1] In the presence of an electric field, linear transport theory predicts a thickness independent growth rate (time independent linear growth law) for the product layers, only depending on the ionic current and on the difference of the cationic transference numbers in the product phases. This is different to the an only thermally activated reaction, were the growth rate depends on the Nernst-Planck coupled conductivities and the reciprocal layer thickness (parabolic growth law).It is shown for this solid state reaction that an electric field will change the thickness ratio of the formed product phase compared to the only thermally activated reaction. The formation of the perovskite phase (YAP) is selectively enhanced when connecting the Y2O3 layer to the cathode side. [2] This may result from the different growth kinetics of the product phases with and without an electric field. The role of grain boundaries as fast diffusion paths is enhanced, resulting in a product layer morphology different to the non-field-driven reaction.[1] C. Korte and B. Franz, Solid State Ionics 368, 115699 (2021)[2] B. Franz and C. Korte, Solid State Ionics 383, 115978 (2022)
|
The record appears in these collections: |