Study of Sintering Temperature on Dielectric Properties of CaCu3Ti4O12 Materials Prepared by Sol-Gel Method

CaCu3Ti4O12 (CCTO) powder was prepared by sol-gel process using acetic acid as a solvent and also as cross-linking agent by varying the sintering temperature (1000-1150 ºC) for 3 h. The dried gels were characterized by TG-DTA and FT-IR techniques. The sintered samples were characterized by XRD, SEM techniques and impedance analyzer for dielectric properties measurement. The sample showed the perovskite structure with small amounts of TiO2 and CuO phases. The best dielectric properties (εr = 1.38 × 104 and tan δ = 0.13 at 10 kHz and room temperature) were observed in the CCTO pellets calcined at 800 ºC for 3 h and sintered at 1100 ºC for 3 h.

Microstructural, Mechanical and Dielectric Properties of CCTO/Epoxy Composite

An attempt has been made to investigate the relationship between different composition of CaCu3Ti4O12 (CCTO)/epoxy to the microstructural, dielectric and mechanical properties respectively. CCTO powder had been produced through solid state reaction method using CaCO3, CuO and TiO2 as the raw materials. They were mixed at stoichiometric ratio and calcined at 1040°C for 10 hours. CCTO powder mixed with epoxy and hardener at different weight percentage (10, 20, 30, 40 and 50 wt%). Microstructure of fracture surface of the composite had been studied using Field Emission Scanning Electron Microscopy (FESEM) and mechanical characterization had been conducted using Universal Testing Machine (UTM). LCR meter Agilent 4284A was used to measure the dielectric properties at 20 Hz to 1 MHz. Increasing CCTO concentration to the composite caused a significant change of dielectric constant which arised from 17.1 to 23.5 at 1 kHz. This arising due to higher concentration of CCTO filler transfer more intrinsic values to the composite. Tensile test shows an increment to stress value from 4 to 17 MPa as the respond on increasing of ceramic filler concentration. High stiffness of CCTO have increased the strength of the composite. The dispersion of higher weight percentage of the CCTO into the epoxy is more compacted than the dispersion of lower weight percentage of CCTO. It is best to mix the higher amount of filler into the polymer matrix to increase the dielectric and strength of the composite material.

Dielectric Properties of CCTO/PVDF Composite Films

To meet the requirement of microelectronic industry, ceramic/polymer composite films made of CaCu3Ti4O12(CCTO) powder as filler and PVDF copolymer as matrix were prepared by solution casting method. The dielectric properties (DP) and morphology of the films were studied by impedance analyzer and scanning electron microscope (SEM) respectively. The dielectric constant could reach 23.96 and loss 0.1082 when mass fraction of CCTO is 50% at 100 Hz. SEM results show that CCTO particles dispersed well in the PVDF matrix. At last, three composite models were used to predict the dielectric constant of the composite films and it is proved that Yamada model fits the experimental data well.

ZnTiO3 Doping Effect on Dielectric Properties of CCTO Ceramics via a Molten Salt Process

CaCu3Ti4O12 (CCTO) powder was prepared by solid-state reaction. CCTO-ZnTiO3 composite ceramic were prepared by reaction of CCTO powder with molten ZnCl2 in air, 400°C. The products were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electric and dielectric properties of CCTO-ZnTiO3 composite ceramic were investigated. It is shown that the ceramic composites have higher grain-boundary resistivity and nonlinear coefficient. The addition of Zn mainly formed in the form of ZnTiO3 also affected the low frequency capacitance values, reduced the CCTO ceramic dielectric loss, which showed a Schottky-type nature of potential barrier. Moreover, the mechanisms involved in the NBLC model were discussed, where it is working with the IBLC model.