Density Evolution. As is generally

Density Evolution. As is generally known, ceramic particles are usually compressed into a green pellet before a hightemperature sintering process. The density of the green body has only a 40−60% relative density; after the conventional thermal sintering, dense ceramic (>90% relative density) is accomplished.22,42−44 In the case of BaTiO3, it is normally sintered at 1200−1400 °C for several hours.14,17,42−44 However, in a significant contrast to this conventional route, it is surprising to notice that dense BaTiO3 ceramics of ∼95% relative density can be achieved at an extraordinarily low temperature (180 °C) in a short time period (∼30 min) by employing the cold sintering process. For a clear demonstration, the density evolution of cold-sintered BaTiO3 as afunction of sintering time is displayed in Figure 1b, together with the corresponding densities measured after annealing at