Effects of synthesis technique on dielectric properties of CaCu3Ti4O12 ceramic

Deficient or excessive CuO‐TiO2 phase influence on dielectric properties of CaCu3Ti4O12 ceramics

“…A remarkable increase in the amount of CuO and TiO 2 phases could be observed, a fact that was expected due to CT/excessive composition of the ceramics. The formation of CuO phase in the CCTO grains boundaries was also seen, this segregation of Cu‐rich phases was responsible for the anomalous growth of the grains in the sintering process and this event has been commonly reported in the literature . The porosity was reduced; however, it is still present.…”

“…This phase could be determinant in the dielectric response of these compounds . Rajabtabar‐Darvishi et al reported a good dielectric response in CCTO samples sintered at 1000°C for 6 hours. The results of their XRD studies revealed a maximum relative intensity of CaTiO 3 phase accompanied by a minimum CuO relative intensity, suggesting this as the possible reason for such results.…”

“…The amount of this phase, about 5%, does not change meaningfully over the CC X T Y O compositions. Rajabtabar‐Darvishi et al reported results of XRD analysis showing that small amounts of CaTiO 3 may exist in CCTO ceramics due to the CCTO phase decomposition at high temperatures.…”

“…Therefore, these suggestions would be more in agreement with the results obtained for CC X T Y O ceramics in this study, since the highest dielectric response with high ε′ values and lower tanδ values were presented by the ceramics with higher amount of CCTO and smaller number of CuO and TiO 2 phases, especially for CC 2.90 T 3.75 O ceramic. The role of the secondary CaTiO 3 phase in the dielectric response to the CCTO samples cannot be ignored, when considering that CaTiO 3 showed a permittivity = 200 . This suggests that this secondary phase acted as barrier layers at the grain boundaries, which contribute to the observed high ε′ values of CCTO ceramics .…”

Conventional and Microwave‐Assisted Sintering of CaCu3Ti4O12 Ceramics Obtained from Coprecipitated Powders

“…It is well known that the electrical properties can be considerably improved when the ceramic has a homogeneous microstructure, which depends on the powder synthesis process. Some studies have reported alternative methods to produce CCTO powders, such as nonoxide precursors calcinations, sol‐gel, mechanical alloying, coprecipitation, microwave heating, molten salts, and semiwet routes. Lu obtained CCTO powders from coprecipitation method starting from aqueous solution of raw materials and precipitation with NaOH using conventional sintering and observed the influence on structural and dielectric properties as a function of ion Cu amount.…”