Voltage–Current Nonlinearity of CaCu₃Ti₄O₁₂ Ceramics

Abstract

Ceramic samples of CaCu3Ti4O12 (CCTO) were prepared and the voltage–current characteristics were investigated. Extremely strong nonlinear behavior, similar to the reported results in literature [Nature Materials 3[11] 774–8 (2004); Appl. Phys. Lett., 89[19] 191907 (2006); Appl. Phys. Lett., 89[21] 212102 (2006); Appl. Phys. Lett., 91[9] 091912 (2007)] was observed. However, we found that this is a measurement artifact due to a thermionic emission current feedback amplification effect. Compared to that of ZnO varistor, the thermionic emission current of CCTO sample is about six orders of magnitude higher and it is feedback amplified due to strong negative temperature coefficient resistance behavior when the CCTO sample is tested with a voltage (or current) source. Eliminating the thermionic emission current feedback amplification effect, the true value of nonlinear coefficient of the CCTO sample is much lower.

High Breakdown Field CaCu3Ti4O12 Ceramics: Roles of the Secondary Phase and of Sr Doping

“…A similar phenomenon is also observed in the CCTO/MgTiO3 [9] and CCTO/CaTiO3 [21] composite ceramics, and it has been attributed to the missing charge carriers. In addition, according to the formula of stored energy U = (ε′Eb 2 )/2, the maximum U calculated for CCTO-0.5 CuAl2O4 and 0.4SCTO-0.6CCTO samples are correspondingly 44.1 and 50.9 kJ·m −3 in this work, which is a great improvement over that of CCTO ceramics of 2-7 kJ·m −3 in previous works [1,3,20,21]. Permittivity and dielectric loss at room temperature of CCTO, CCTO-0.5CuAl 2 O 4 , and 0.4SCTO-0.6CCTO ceramics are presented in Figure 4.…”

“…Results of the breakdown field and the nonlinear coefficient are shown in Figure 3b. It can be found that the CCTO-0.5CuAl 2 O 4 and 0.4SCTO-0.6CCTO samples show an extremely high breakdown electric field E b of about 20 kV·cm −1 , which is almost 10 times of former works in both pure CCTO ceramics [3,20] Energies 2017, 10, 1031 5 of 10 and CCTO-based composite ceramics [9]. The breakdown field of 0.4SCTO-0.6CCTO samples sintering at 1000 • C for 5 h even reaches 23.8 kV·cm −1 and that of CCTO-0.5CuAl 2 O 4 samples also achieves 21 kV·cm −1 , which are the highest values ever reported.…”

“…After CCTO powder was suspended in an Al(NO 3 ) 3 aqueous solution, the suspension was quantitatively titrated with NH 4 OH to obtain Al(OH) 3 precipitation on the surface of CCTO particles. The obtained powder was dried and calcined at 950 • C for 4 h to dehydrate Al(OH) 3 into Al 2 O 3 . Then, powder was pressed into pellets with a diameter of 12 mm and a thickness of 1.6 mm.…”

“…In addition to CDC, non-ohmic characteristic has also been found in CCTO ceramics [2], which is promising in applications of energy storage capacitors and over-voltage protection devices. Both the CDC property and non-ohmic characteristics are associated with defect-related double Schottky barrier between the semiconducting grains and insulating grain boundaries [3][4][5]. The Schottky barrier blocks charge transport at grain boundaries, resulting in high nonlinear coefficient [2] and active dipole movement for CDC property in an internal barrier layer capacitor (IBLC) model [6].…”

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

“…The Schottky barrier characteristic and non-ohmic property of CCTO ceramics can be interpreted by using ZnO varistor for reference [15][16][17]. In our earlier works, dimensional effect was introduced to describe the variation of the breakdown field and nonlinear coefficient with the thickness in ZnO varistor ceramics, and an inflection behavior can be found at a critical thickness [18][19][20].…”