The dimensional effect of dielectric performance in CaCu3Ti4O12 ceramics: Role of grain boundary

Grain boundary engineering that induces ultrahigh permittivity and decreased dielectric loss in CdCu3Ti4O12 ceramics

“…The details of the results are provided in Table . The unknown phases in the grain boundaries of the CdCTO‐04Zn ceramics are Cu/Zn‐enriched phases, while that in the CdCTO ceramics is a Cu‐enriched phase …”

“…The unknown phases in the grain boundaries of the CdCTO-04Zn ceramics are Cu/Zn-enriched phases, while that in the CdCTO ceramics is a Cu-enriched phase. [26][27][28][29][30][31][32][33][34] The frequency-dependent dielectric behavior of the CdCu 3−x Zn x Ti 4 O 12 ceramics is shown in Figure 4A; the inset shows an enlarged view of the frequency-dependent (40-10 4 Hz) dielectric loss tangent. The dielectric permittivity maintains a high value above 2.0 × 10 4 and seems to be frequency independent when the measured frequency is below 10 5 Hz, while a sharp decrease to ~100 occurs when the frequency reaches 10 7~1 0 8 Hz.…”

“…[15][16][17][18]46,47 According to the IBLC model, double Schottky barriers from n-type grains to insulating grain boundaries, and vice versa, can form. Without a dc bias, the Schottky barrier height Φ gb can be expressed as follows 34,45,[48][49][50] : where q is the electronic charge, N d is the charge carrier concentration, and N s is the density of the interface states.…”

“…Since the electrical conduction of ACTO ceramics follows a field-assisted thermionic emission process across the Schottky barrier at high temperature, 34,42,[49][50][51] the barrier height at grain boundaries Φ gb can then be evaluated by the activation energy of electric conduction E gb . Figure 6D displays the value of E gb as a function of Zn content.…”

Breakdown Characteristics of Varistor Ceramics

“…This further results in current localization, which causes electrical puncture, thermal cracking, or even thermal runaway [14]. In addition, dimensional effect, which exhibits as the thickness dependence of breakdown field, is found in not only ZnO ceramics but also CCTO ceramics [15][16][17]. It is found that breakdown field and nonlinear coefficient are significantly decreased below a critical thickness, which brings much trouble in designing.…”