field-assisted processing, synthesis, sintering, microstructure, dielectric response
Processing of materials in the form of ceramics normally involves several steps including calcination at a relatively low temperature for synthesis of the end-product powder and sintering at a high temperature for densification. The work we have been developing introduces a novel approach enabling synthesis plus sintering of materials in a single running experiment by using electric fields, ending with dense ceramics that display grains noticeably finer than in conventional processing. This new paradigm is fully illustrated with experiments conducted on amorphous CaCu3Ti4O12 precursor powder, shown to experience, on heating, crystallization through intermediate phases, followed by chemical reaction leading to synthesis of the end-product powder, plus densification depending on field adjustment. The processing time and furnace temperature are considerably reduced, demonstrating that enhanced synthesis and sintering rates applied under field input. Similar results found in Bi2/3Cu3Ti4O12 are also shown. The different factors that may contribute to this unique scenario, including Joule heating, defect generation, and reduction of free energy for nuclei formation promoted by the applied field, are briefly discussed. Overall, the findings we bring here are exclusive as they show an exploitable way that allows rapid processing of materials with good control over particle and grain coarsening.
Tsinghua University Press
Lílian M. JESUS, Ronaldo S. SILVA, Jean-Claude M’ PEKO. Ultrafast synthesis and sintering of materials in a single running experiment approach by using electric fields. Journal of Advanced Ceramics 2019, 8(2): 265-277.