Zhao Quanliang

Structural and Electrical Properties of PZT/PVDF Piezoelectric Nanocomposites Prepared by Cold-Press and Hot-Press Routes

The 0-3 PZT/PVDF piezoelectric composites are prepared separately by hot-press and cold-press processes. The effects of the PZT content and the shaping-process on the composites are studied. The experimental results indicate that composites with 70% PZT nanopowders prepared by the hot-press method exhibit excellent piezoelectric and dielectric properties. The maxima of dss and e of the composites prepared by hot-press method are about 30% and 65% higher than those prepared by the cold-press method, respectively. This is mainly attributed to the favourable coupling of the two materials in the process of the hot press and the formation of the β-type PVDF, which possesses better electric properties.

Structural and electrical properties of Nd ion modified lead zirconate titanate nanopowders and ceramics

A modified sol-gel method is used for synthesizing Nd ion doped lead zirconate titanate nanopowders Pb1–3x/2NdxZr0.52Ti0.48O3 (PNZT) in an ethylene glycol system with zirconium nitrate as zirconium source. The results show that it is critical to add lead acetate after the reaction of zirconium nitrate with tetrabutyl titanate in the ethylene glycol system for preparing PNZT with an exact fraction of titanium content. It has been observed that the dopant of excess Nd ions can effectively improve the sintered densification and activity of the PNZT ceramics. Piezoelectric, dielectric and ferroelectric properties of the PNZT ceramics are remarkably enhanced as compared with those of monolithic lead zirconate titanate (PZT). Especially, the supreme values of piezoelectric constant (d33) and dielectric constant () for the PNZT are both about two times that of the monolithic PZT and moreover, the remnant polarization (Pr) also increases by 30%. According to the analysis of the structures and properties, we attribute the improvement in electrical properties to the lead vacancies caused by the doping of Nd ions.

Mechanical Reinforcement and Piezoelectric Properties of PZT Ceramics Embedded with Nano-Crystalline

The double-scale lead zirconate titanate (PZT) piezoelectric ceramics were prepared by the solid state processing with PZT nano-crystalline and micro-powder. The microstructures, electrical and mechanical properties of the double-scale PZT are investigated. All the sintered ceramics exhibit a single perovskite structure and the grain size of the double-scale PZT reduces due to the incorporation of PZT nano-crystalline. Compared to normal PZT, the mechanical properties increase significantly and the piezoelectric properties decrease slightly. Mechanisms responsible for the reinforcement of the double-scale PZT are discussed.

Preparation and Ferroelectric Properties of Double-Scale PZT Composite Piezoelectric Thick Film

Dense and crack-free double-scale lead zirconate titanate (Pb(Zr0.52Ti0.48)O3, PZT) composite piezoelectric thick films have been successfully fabricated on Au/Cr/SiO2/Si substrates by a modified sol-gel method. The XRD analysis indicates that the thick film possesses a single-phase perovskite-type structure. The SEM micrograph shows that the surface is crack-free and the cross section is dense and clear. The thickness of the PZT thick film is about 4 μm. It also exhibits good ferroelectric properties, and has high direct current compression resistant properties. At the test frequency of 1kHz, the film has the coercive field of 50 kV/cm, the saturation polarization of 54 μC/cm2 and the remnant polarization of 30 μC/cm2.

Electrical Properties of Lead Zirconate Titanate Thick Film Containing Micro- and Nano-Crystalline Particles

We report the ferroelectric, dielectric and piezoelectric properties of a dense and crack-free lead zirconate titanate (Pb(Zr0.52Ti0.48)O3, PZT) thick film containing micro- and nano-crystalline particles. The results show that these electrical properties are dependent strongly on the annealing temperature and film thickness. For the different-annealing-temperature and different-thickness films, the higher-annealing-temperature thicker ones show the larger remnant polarization and smaller coercive field. The dielectric results show that relative dielectric constant achieves the largest value at annealing temperature of 700°C, and increases with the increasing film thickness. For the piezoelectric properties, the longitudinal piezoelectric coefficient increases linearly with the film thickness increasing and the 4-μm-thick PZT film shows the largest value of about 200.65 pC/N. Therefore, the PZT thick films present good electric properties and enlarged potential in MEMS applications.

Electromechanical Properties of Microcantilever Actuated by Enhanced Piezoelectric PZT Thick Film

Pb(Zr0.53, Ti0.47)O3 (PZT) films with thicknesses of 0.8μm, 2μm and 4μm are prepared by a sol-gel method and their longitudinal piezoelectric coefficients are analysed. The results show that the PZT thick films, whose density is closer to bulk PZT, has the better crystallization, with d33 and density much larger than those of PZT thin films. A piezoelectric microcantilever actuated by a 4-μm-thick PZT film is fabricated and its displacement is measured in different frequencies and voltages. The displacement increases linearly with the increasing bias, and the maximum displacement of 0.544 μm is observed at 30kHz for 5V bias. The resonant frequency obtained in the experiment matches quite well with the theoretical result, and it is shown that the resonant frequency of PZT microcantilever could be controlled and predicated.

Enhanced mechanical behaviour of lead zirconate titanate piezoelectric composites incorporating zinc oxide nanowhiskers

This paper reports that the lead zirconate titanate (PZT) piezoelectric composites incorporating zinc oxide nanowhiskers (ZnOw) were prepared by the conventional solid state processing. The whisker-dispersed PZT composites (PZT/ZnOw) presented a significant enhancement in the mechanical properties such as Youngs modulus, tensile strength and compressive strength. Especially, the compressive strength increased from 153 MPa for the PZT to 228 MPa for the PZT/ZnOw composites. The reinforcement mechanism in strength of the composites was discussed. The mechanical quality factors of the PZT/ZnOw composites increased considerably, while the piezoelectric constants and electromechanical coupling coefficient decreased slightly. The composites with good electrical and excellent mechanical properties are promising for further applications.

Nitrogen Dioxide Sensing Properties and Mechanism of Copper Phthalocyanine Film

Copper phthalocyanine film, a p-type organic semiconductor, is synthesized by vacuum sublimation and its surface morphology is characterized by SEM. A silicon-based copper phthalocyanine film gas sensor for NO2 detection is fabricated by MEMS technology. The results show that the resistance and sensitivity of copper phthalocyanine film decrease obviously as the NO2 concentration increases from 0 ppm to 100ppm. However, the sensitivity nearly keeps a constant of 0.158 between 30 ppm and 70 ppm. The best working temperature of the gas sensor is 90° G for NO2 gas concentrations of 10 ppm, 20 ppm and 30 ppm, which is much lower than that of general metal oxide gas sensor.

Stationary Fluid Dynamic Behaviour of V-Shaped Diffuser/Nozzle Elements for Valveless Micropump

A novel type of V-shaped (isosceles triangle cross-section) diffuser/nozzle element is proposed for use for valveless micropump. Stationary fluid dynamic behaviour of V-shaped diffuser/nozzle elements in a valveless micropump is investigated by experiment and simulation. Both the results agree well with each other when the Reynolds number is higher than 100 and the pressure loss coefficient ratio of micropump nearly always keeps a constant. For a single V-shaped diffuser, the general trends of variation of pressure loss coefficient with opening angle and Reynolds number are opposite in small and large angles. Compared with conical and flat-wall diffusers, V-shaped diffuser shows the smallest pressure loss when the Reynolds number is 200.

Morphology and properties of PZT nanoparticle modified PZT thick film by alternative spinning

ABSTRACT The present work focused on the study of morphology, crystalline structure and the ferroelectric properties of PZT thick film, which was modified with PZT nanoparticles and prepared by alternative spinning technique. The experimental results showed that the alternative spinning technique not only improved the film thickness, but also solved the problem on the membrane surface roughness of the thick film prepared by PZT 0–3 composite sol method. The results also confirmed that the electrical properties depended strongly on the annealing temperature and film thickness. With the increase of the annealing temperature, Pr increased and Ec changed inconspicuously. When the thickness of PZT thick film increased, Ec decreased but Pr increased. For the 4 µm-thick film, Ec and Pr were 23 kV/cm and 60 µC/cm2, respectively. These results suggest that the modified PZT thick film has a potential application on the fabrication of micro-devices because it provides good ferroelectricity, dielectricity and piezoelectricity.