Q.G. Chi

Enhanced performance of Pb0.8La0.1Ca0.1Ti0.975O3/Pb(Nb0.01Zr0.2Ti0.8)O3 multilayer thin films for pyroelectric applications

Taking advantage of the relatively low temperature crystallization and high orientation of thin films of Pb0.8La0.1Ca0.1Ti0.975O3 (PLCT), growth of a highly (100)-oriented PLCT/Pb(Nb0.01Zr0.2Ti0.8)O3 (PNZT) multilayer film on a Pt/Ti/SiO2/Si substrate is achieved at a temperature as low as 450 °C. The interfacial diffusion in the multilayer film is decreased by the low temperature of crystallization. A relatively low dielectric constant and high pyrocoefficient are simultaneously achieved in the highly (100)-oriented PLCT/PNZT multilayer film. The high figure-of-merit obtained for this multilayer film make it a good candidate for application in pyroelectric thin-film devices.

Enhanced performance of core-shell-like structure Zr-doped CaCu3Ti4O12 ceramics prepared by a flame synthetic approach

Zr-substituted CaCu3Ti4O12 ceramics were fabricated by a sol–gel flame synthetic approach. The influence of microstructure on the dielectric response of the ceramics has been investigated. It is found that CaCu3Ti4−xZrxO12 ceramics with a core-shell-like structure are obtained up to x = 0.05, and the thickness of the interphase region decreases with increasing Zr content. The maximum dielectric constant value is up to ∼6 × 104 for x = 0.05 at 1 kHz at room temperature. The high dielectric constant is connected to grain boundary effects, and the enhanced giant dielectric response with Zr substitution is attributed to a locally stretched lattice near Zr on the B-site and the resulting polarization switching of electric dipole moments.

Investigation on dielectric properties of the polyimide- based composite films with high permittivity

CaCu3Ti4O12 (CCTO) and Zr-doped CaCu3Ti3.95Zr0.05O12 (CCTZO) particles with a giant dielectric permittivity were used as filler to prepare Polyimide (PI)-based composites, respectively. Dielectric properties of CCTO/PI and CCTZO/PI composite films have been investigated comparatively. It is found that the dielectric properties of two kinds of composite films with low concentration filler loading have independence on frequency and temperature, while the dielectric permittivity of two kinds of composite films increases remarkably with increasing concentration of filler loading(>20%) and temperature. The dielectric permittivity of CCTZO/PI composite film with a 40% filler loading reaches up to 70 at 10 Hz, which is higher than that (43) of CCTO/PI composite film with the same concentration filler loading. It is also found that the dielectric permittivity of CCTZO/PI composite film can reach about 260 at 150 °C when the concentration of CCTZO loading is 40 vol%. The conductive properties of two kinds of composite films increase with increasing frequency, temperature and concentration of filler loading. The study indicates that dielectric and conductive properties are closely related to the polarization between filler and PI matrix and semiconductive network supported by the percolation theory.

Improving dielectric properties of PVDF composites by obtaining the BT-Ni particles

In the rapid development of modern science and technology, the dielectric materials with more extraordinary performance were extremely demanded in the electronic system fields. Nowadays, outstanding-performance polymers, which possess a high dielectric constant and flexibility but low dielectric loss have attracted great attention owing to their potential application in many cutting-edge industries, including microelectronics, aerospace, and aviation. In general, the polymers possess excellent flexibility and high breakdown strength, but their applications was limited by the low dielectric permittivity. Numerous efforts have been made to improve the dielectric permittivity of dielectrics by incorporating ceramic additives into polymer matrix. Unfortunately, the high dielectric permittivity needs high filler loading, which causes them to lose their flexibility and decreased breakdown strengths. Herein, the Ni nanoparticles was deposited on the surface of the BT particles to obtain the BT-Ni particles by electroless plating method. The phase composition and morphology were analyzed by X-ray diffraction and scanning electron microscopy, and the effects of BT-Ni filler on the dielectric properties of the composites were investigated in detail. It can be found that the high dielectric permittivity of the composites increased to 61 at 100 Hz when the content of BT-Ni filler was 20vol.%, which is 2.54 times higher than that of 20vol.% BT/PVDF (24) and even greater than that of 40vol.% BT/PVDF (56). The Ni nanoparticles was strong interaction deposited on BT particles, and this structure can effectively suppress the probability of the Ni nanoparticles to form a conductive networks in the PVDF polymer matrix, which can greatly depress the increase of dielectric loss tangent and conductivity of the BT-Ni/PVDF composites. These results indicated that the dielectric constant of the composites can be significantly improved by incorporating Ni conducting particles into the polymer matrix and that the interfacial polarization effect is an important feature of BT-Ni/PVDF composites. This work provides a simple and effective way for preparing nanocomposites with enhanced dielectric properties for use in the electronics industry.

The effect of CaCu 3 Ti 3.95 Zr 0.05 O 12 fillers on microstructure and dielectric behaviour of CaCu 3 Ti 3.95 Zr 0.05 O 12 /Polyimide composites

In the present study, the microstructure and dielectric properties of composites comprising Polyimide (PI) and CaCu3Ti4O12 (CCTO) or CaCu3Ti3.95Zr0.05O12 (CCTZO) particles have been investigated. CCTO and CCTZO were employed separately and investigated comparatively. The effective dielectric constant of the composite containing 40vol.% CCTZO filler is over 50 at 40°C (102 Hz), which is substantially higher than that of the composite containing CCTO. For the composite containing 40vol.% CCTZO, the dielectric constant and the conductivity increases sharply with increasing temperature. The mechanism of high dielectric constant was investigated finally.