Abstract: CaCu3Ti4O12 (CCTO) has attracted great attention because of its potential application in microelectronic devices, as showing very high ?? values (~ 12,000) with good stability from room temperature to 300 °C. This material is usually prepared through conventional synthesis (solid-state reaction) at 1000 °C followed by sintering at 1100 °C, for dwell times of several hours. These high annealing temperatures and times lead to ceramics with micro-sized grains, exceeding significantly 1.0 µm in most cases. On the other hand, field-assisted flash sintering, which consists of applying an electric field (E) on the sintering body during thermal treatment, allows production of high-density and fine-grained ceramics in a matter of seconds, at furnace temperatures well below those required in conventional sintering. In light of these facts, field-assisted flash sintering was considered for producing high-quality CCTO electroceramics, from a powder originally synthesized via a modified polymeric precursor method and calcined at 800 °C for 2 h. The study includes analyzing the dynamics of material shrinkage and densification. With increasing temperature, three distinct regimes were distinguished: 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, under field action, sintering of the material was achieved 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 physical mechanism behind each regime and the extent to which the rise in sample temperature induced by the applied field (Joule heating) is determinant are also discussed. Finally, a correlation was found between the microstructural characteristics achieved during sintering and the dielectric response measured.
Seminarista: Lílian Menezes de Jesus, doutoranda do CCMC
Data e horário: Dia 15/10/2015, quinta feira, das 10 h às 11 h
Local: Sala 14, Prédio Administrativo do IFSC (embaixo do anfiteatro Prof. Sérgio Mascarenhas)
