To better illustrate the processing

To better illustrate the processing−structure−property relationship, the dielectric properties of the cold-sintered and subsequently annealed BaTiO3 ceramics are investigated (Figure 5). The dielectric spectra are recorded during a cooling process at a temperature range that covers the ferroelectric-to-paraelectric Curie−Weiss transition of BaTiO3 at ∼120 ℃.49 In the case of cold-sintered ceramic (Figure 5a) and that after annealing at 700 °C (Figure 5b), the Curie transition is barely noticed, and a high dielectric loss is seen through both the magnitude and the frequency dissipation. These observations are given by the preservation of a significant portion of nanoparticles with a cubic phase, as well as the prevalence of a glassy phase. Further increasing the annealing temperature not only facilitates the formation of BaTiO3 crystallites at the expense of the glassy phase but also triggers a thorough cubic-to-tetragonal phase transformation, through removal of bulk hydroxyls and obtaining larger grain sizes. In response to the microstructural evolution, the dielectric anomalies develop with sharp Curie transition peaks, as well as reduced frequencydispersion (Figure 5c,d). Not only does the annealing process have a significant influence on the crystallographic evolution, but it is also effective for the dielectric performance enhancement. In the case of the room-temperature dielectric constant (1 kHz), it is initially increased from ∼170 to ∼450 after annealing at 700 °C and then is enhanced up to ∼1760 after annealing at 900 °C.