Flash sintering of ionic conductors: delay time before current flash and role of electrode reaction

Reference Presenter Authors
12-027 Marlu Cesar STEIL STEIL, M.C.(Univ. Grenoble Alpes - CNRS);

Flash sintering (FS) is an Electrical Current Activated Sintering technique able to densify ceramic materials in a few seconds, at much lower furnace temperatures than conventional sintering. The capability of this sintering process has been reported for a large set of ionic conductive ceramics and recently for composite materials. Since no die is used, the current mandatorily flows through the sample and the flash process is characterized by an abrupt increase in electrical current through the sample accompanied by shrinkage and densification. The FS elementary mechanisms are not yet fully understood. It has been recognized that, in “isothermal experiments”, the flash densification stage (“flash stage”) is observed after a delay time during which no macroscopic densification is observed (“pre-flash stage”). According to the literature and to our previous works1,2, the effective electrical conductivity of the sample is a key parameter of the flash effect. Another specific parameter with the ceramic ion conductors results from the very different nature of their electric current carriers: the necessity of a charge exchange between the electrical circuit (electrons) and the ionic charge carriers in the ionic ceramic3. This phenomenon, called “electrode reaction” in solid-state electrochemistry, differs from an ion carrier to another. This work is dedicated to the study of the influence of different parameters that govern the pre-flash stage and the electrode reaction (furnace atmosphere, DC or AC polarization, temperature, voltage and electrode material) on the FS of different ionic ceramics (zirconia and ceria based materials, beta-alumina).

1Steil et al. J Eur. Cer Soc, 33, 2013; 2Bichaud.et al. J Eur Cer Soc, 35, 2015; 3Caliman et al. J Eur Cer Soc, 36, 2016

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