Electric field-assisted flash sintering of CaCu3Ti4O12: Microstructure characteristics and dielectric properties

The electric field-assisted flash sintering method recently introduced in the literature was here considered for producing high-quality CaCu3Ti4O12 electroceramics, from a powder originally synthesized by a Pechini-derived method and calcined at 800 °C for 2 h. The study included analyzing the dynamics of material shrinkage and densification. With increasing the electric field (E), three distinct regimes were observed: a conventional-like sintering behavior for E < 15 V/cm, followed by a region of accelerated (fast-dominated) sintering for 15 ≲ E < 30 V/cm, and then the flash-dominated regime, for E ≳ 30 V/cm, where sintering is not only accelerated but occurs suddenly. In consequence, sintering of the material under field input takes place at furnace temperatures sensibly lower, reaching a value as low as 750 °C for E = 60 V/cm versus 1050 °C in conventional processing. The probable physical mechanism behind each regime, including the role of the rise in sample temperature induced by the applied field (Joule heating), is also discussed. Finally, a correlation was found between the microstructure characteristics achieved during sintering and the dielectric response measured.