Zhaorong Huang

Low temperature crystallization of lead zirconate titanate thin films by a sol-gel method

Pyroelectric lead zirconate titanate (PZT) thin films have been prepared by a sol-gel method and characterized by x-ray diffraction and transmission electron microscopy (TEM). A metastable Pt3Pb intermetallic phase has been identified. The formation of this metastable phase was found to depend on the drying temperature, the thickness of the as-deposited film, annealing temperature, and annealing time. Perovskite PZT was found to nucleate on top of the intermetallic phase, rather than directly on Pt. The improved lattice match between the intermetallic (a0=4.05 A) and perovskite PZT(a0=4.035 A) as compared to between Pt(a0=3.9231 A) and the perovskite is believed to substantially reduce the activation energy for the nucleation of perovskite on Pt. Using this effect, (111) perovskite PZT has been grown at a temperature as low as 440 °C. The formation of the intermetallic phase is believed to facilitate the (111) film orientation. The growth kinetics of the PZT were analyzed using the Avrami model, and from ...

Structural development in the early stages of annealing of sol–gel prepared lead zirconate titanate thin films

Lead zirconate titanate (PZT) thin films on platinized silicon were fabricated and their structural development upon annealing was characterized by x-ray diffraction and transmission electron microscopy (TEM). The amount of a transient intermetallic phase Pt3Pb was found initially to increase with annealing time and to decay after reaching a maximum. The kinetic process of growth and decay was simulated by using the Avrami equation. The Avrami coefficient n and growth rate constant k were determined by comparing the experimental results and the simulated curves, from which activation energies of 40 and 145 kJ/mol were obtained for the growth and decay of the intermetallic Pt3Pb phase, respectively. The perovskite PZT was found by using TEM to nucleate epitaxially on top of the Pt3Pb phase. Evidence is presented that the Pt3Pb phase plays a major role in determining the crystallite’s orientation at the nucleation stage of the perovskite PZT. This depends strongly on the annealing temperature and the orient...

Fabrication and modeling of high-frequency PZT composite thick film membrance resonators

High-frequency, thickness mode resonators were fabricated using a 7 /spl mu/m piezoelectric transducer (PZT) thick film that was produced using a modified composite ceramic sol-gel process. Initial studies dealt with the integration of the PZT thick film onto the substrate. Zirconium oxide (ZrO/sub 2/) was selected as a diffusion barrier layer and gave good results when used in conjunction with silicon oxide (SiO/sub 2/) as an etch stop layer. Using these conditions, devices were produced and the acoustic properties measured and modeled. The resonators showed a resonant frequency of about 200 MHz, an effective electromechanical coupling coefficient of 0.34, and a Q factor of 22. Modeling was based on a Mason-type model that gave good agreement between the experimental data and the simulations. The latter showed, for the PZT thick film, an electromechanical coupling coefficient of 0.35, a stiffness of 8.65/sup */10/sup 10/ N.m/sup -2/ and an e/sub 33/,/sub f/ Piezoelectric coefficient of 9 cm/sup -2/.

Theoretical modeling on the magnetization by electric field through product property

Multilayer composites of piezoelectric and magnetostrictive materials can be designed to exhibit the magnetoelectric (ME) effect. This ME effect can be realized as an electric polarization induced by a magnetic field (called MEH effect) or a magnetization by an electric field (called MEE effect). Theoretical modeling of the MEE effect for 2-2 connectivity composites has been developed for three different boundary conditions for perfect coupling at the interface. The calculated MEE coefficients using material properties of piezoelectric lead zirconate titanate and magnetostrictive Terfenol-D are a few orders of magnitude larger than those of single phase ME materials and the calculated values are compared with experimental results in the literature.

Growth and characterisation of lead zirconate titanate (30/70) on indium tin oxide coated glass for oxide ferroelectric-liquid crystal display application

Abstract The growth and characterisation of sol-gel lead zirconate titanate (PZT) (30/70) thin films on indium tin oxide (ITO) coated glass have been investigated using X-ray diffraction (XRD), transmitting electron microscopy (TEM) and atomic force microscopy (AFM). Perovskite crystallised at 550°C in a random orientation, and all films showed characteristic rosette formations. A seeding and crystallisation model has been proposed to describe the rosette formation process, which is based on the ease of PbO diffusion through the film. The effect of drying temperature on annealed film properties has been examined and when optimised has been shown to improve electrical properties and film flatness. Incorporation of the PZT films into small prototype liquid crystal displays has been done. Application of pulsed poling voltages to the displays has resulted in bulk alignment of the liquid crystal adjacent to poled regions of the PZT layer which remained after the poling voltages were removed.

Ultrahigh resolution of lead zirconate titanate 30/70 domains as imaged by piezoforce microscopy

iezoforce microscopy (PFM) has been used to determine the domain structure of lead zirconate titanate (PZT) (30/70) on an indium tin oxide (ITO)/glass substrate with a TiO2 boundary layer. The PZT nucleates into the perovskite form in a random crystallographic manner, which leads to a random domain structure in the final film. Using PFM it has been possible to visualize the domain structure of the PZT and determine that the domain structure has features as fine as 8 nm herringbone patterns. The possible impact of these structures for future devices utilizing nanoscale features of PZT and especially FeRAM developments is highlighted.

Effect of the particle size in PZT precursor sols on the orientation of the thin films

Abstract In the sol–gel processing of the ferroelectric thin films of PbZr x Ti 1- x O 3 (PZT), solution precursor characteristics have long been considered as factors which affect thin film microstructure. In this study, the structures of PZT precursor sols before and after hydrolysis were characterised by using NMR (nuclear magnetic resonance), PCS (photon correlation spectroscopy), and SAXS (small angle X-ray scattering) techniques as well as the measurement of the rheological properties of the PZT precursor solutions. The measurements discovered that alkoxy ligands which were bonded to metals were completely replaced by acetate ligands in the unhydrolysed sols. The particles in our PZT sols are chain-like and their average size increases linearly after hydrolysis on a logarithmic scale due to the hydrolysis and condensation reactions. To examine the relationship between the film orientation and the particle size in the precursor sols, the films were fabricated with different particle sizes and then annealed at 480°C. The preferred orientations were investigated using X-ray diffraction.

Comparative measurements of piezoelectric coefficient of PZT films by berlincourt, interferometer, and vibrometer methods

Chemical solution deposition (CSD) techniques were used to prepare lead zirconate (Zr) titanate (Ti) (PZT) thin films with Zr/Ti ratios of 30/70 and 52/48. Usually CSD processing is restricted to making crack-free, single-layer films of 70-nm thick, but modifications to the sol-gel process have permitted the fabrication of dense, crack-free, single layers up to 200 to 300 nm thick, which can be built-up into layers up to 3-mum thick. Thicker PZT films (>2-mum single layer) can be produced by using a composite sol-gel/ceramic process. Knowledge of the electroactive properties of these materials is essential for modeling and design of novel micro-electromechanical systems (MEMS) devices, but accurate measurement of these properties is by no means straightforward. A novel, double-beam, common-path laser interferometer has been developed to measure the longitudinal (d33) piezoelectric coefficient in films; the results were compared with the values obtained by Berlincourt and laser scanning vibrometer methods. It was found that, for thin-film samples, the d33,f values obtained from the Berlincourt method are usually larger than those obtained from the interferometer and the vibrometer methods; the reasons for this are discussed

Development of piezoelectric actuated mechanism for flapping wing micro-aerial vehicle applications

Abstract Abstract A piezoelectric actuated two-bar two-flexure motion amplification mechanism for flapping wing micro-aerial vehicle application has been investigated. f r*A as an optimisation criterion has been introduced where f r is its fundamental resonant frequency of the system and A the vibration amplitude at the wing tip, or the free tip deflection at quasi-static operation. This criterion can be used to obtain the best piezoelectric actuation mechanism with the best energy transmission coefficient for flapping wing micro-aerial vehicle applications, and is a measurable quantity therefore can be compared with experimental results. A simplified beam model has been developed to calculate the fundamental resonant frequency for the full system consisted of piezoelectric actuator, motion amplification mechanism and the attached wing and the calculated values were compared with the measured results. A clear trend of the criteria f r*A varying with the two-flexure dimension, stiffness and setting angle have been obtained from the measured data and also the predicted results as a guideline for optimal design of the system.

Pyroelectric effect enhancement in laminate composites under short circuit condition

The pyroelectric coefficients of laminate composites under short circuit condition have been investigated by analytical modeling and numerical simulations. Indicators for various pyroelectric/non-pyroelectric material pairs that can be utilized to determine their pyroelectric coefficient enhancement credentials have been identified. Six pyroelectric materials were paired with six non-pyroelectric/elastic materials and their pyroelectric coefficient enhancement potential and figure of merit for efficiency were investigated. The best performing partnership out of the 36 pairs was lead zirconate titanate (PZT5H)-chlorinated polyvinyl chloride thermoplastic (CPVC) for thickness ratios (R) below 0.09 and PZT5H-zinc for R larger than 0.09 with both demonstrating total pyroelectric coefficient of approximately −20×10−4 C m−2 K−1 at R=0.09, which corresponds to approximately 300% increase in the coefficient. PZT5H-CPVC also showed maximum of 800% rise in the pyroelectric coefficient while figure of merit for effi...