Excellent Capacitor–Varistor Properties in Lead-Free CaCu₃Ti₄O₁₂–SrTiO₃ System with a Wrinkle Structure via Interface Engineering

Abstract

Lead-free perovskite CaCu 3 Ti 4 O 12 (CCTO) dielectrics are extremely important candidates for capacitor−varistor dual-function materials. However, their overall success in applications is somewhat controlled by the longstanding issues such as relatively large dielectric loss and insufficiently high electric breakdown field. Herein, we report the success in the preparation of an optimized lead-free (1−x)CaCu 3 Ti 4 O 12 −xSrTiO 3 (CCTO− STO) composite system with improved dielectric and nonlinear properties via interface engineering. Interestingly, looking closer at the grain boundaries using transmission electron microscopy, it is found that an obvious interface region with a transition layer of a wrinkled structure is formed between the CCTO matrix phase and STO dopant phase. Significantly, all the composite ceramic samples present high permittivity in the order of about 10 3 to 10 4 , and the 0.9CCTO−0.1STO composite ceramic sample exhibits a lower dielectric loss of about 0.068 at room temperature and at 1 kHz. Excitingly, the optimized 0.9CCTO−0.1STO composite ceramic sample also exhibits a remarkably elevated breakdown field strength of about 14.03 kV/cm and a large nonlinear coefficient of about 16.11. The improvement in nonlinear properties with a high breakdown field strength and large nonlinear coefficient could be attributed to the interfacial effect in the composite structure, originating from the formation of the transition layer with a wrinkle structure at the interface between CCTO and STO phases. Such effects can result in great electrical heterogeneity caused by the higher resistance of the grain boundary and the enhanced potential barrier at the interface region. The new insights on the formation of the interfacial wrinkle structure near the phase boundaries of the CCTO−STO composite system and their effects on improvement of electrical properties can stimulate future research on lead-free CCTO−STO-based systems toward capacitor−varistor dual-function applications and may offer an effective way to design other lead-free dielectric materials as well.

Giant dielectric response and relaxation behavior in (Tm + Ta) co-doped TiO2 ceramics

“…Generally, the potential barrier height at the grain boundary can be also evaluated as the E gb value. 31 It can be seen that the change tendency of the E b is consistent with the E gb . The variation of dielectric properties with frequency at different temperatures is given in Fig.…”

“…According to the IBLC mechanism, an equivalent circuit consisting of two series-connected RC elements can fit an impedance spectrum with electrical inhomogeneities of grains and grain boundaries. [31][32][33] To achieve more accurate impedance data, the impedance spectra were fitted using the Z-View program to obtain the corresponding R gb and R g , as shown in Fig. 6(b and c).…”

Preparation of zinc oxide/poly-ether-ether-ketone (PEEK) composites via the cold sintering process

“…PEEK polymer has a large number of applications in various fields, including the aerospace, medical devices, electronics, automobile industries, etc. Zinc oxide (ZnO) is a semiconducting material with a wideband gap of ~3.37eV [6][7][8][9]. It has a large exciton binding energy, high transparency, and excellent luminous properties at room temperature.…”

Effect of ZrO2 Doping on the Microstructure and Dielectric Properties of Ca0.97Y0.03Cu3Ti4-xZrxO12 Ceramics

“…Thirdly, the dielectric properties of CCTO ceramics are in uenced by the generation of intergranular phases. When the concentration of the dopant increases, the inclusion phases are segregated out in CCTO to form the intergranular phase, such as Ba 2+ [24], SrTiO 3 [25], etc. These intergranular phases inhibit crystal growth and increase the resistance of grain boundaries.…”

“…These intergranular phases inhibit crystal growth and increase the resistance of grain boundaries. These studies not only provided experimental basis for the mechanism of giant permittivity, but also provided ideas and methods for improving the ε r and reducing the tanδ of CCTO ceramics [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”