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[en] The properties of several Pb(ZrTi)O3 (PZT) piezoceramics under compressive uniaxial stresses were characterized. It was observed that uniaxial stresses have a marked effect on the soft PZT materials, including reducing the piezoelectric coefficients and depoling the samples at relative low stress levels. The effect of the uniaxial stresses on the properties of hard PZT close-quote s is more complicated because the domain structure of the materials can be changed substantially without depoling the samples. Therefore, under a compressive stress along the poling direction, the piezoelectric and electromechanical coupling factor can be increased markedly due to both the increased non-180 degree domain boundary motions and the deaging effect. In addition, the experimental results support the notion that the difference between a hard PZT and a soft PZT lies in the types of defects introduced by dopants. Immobile defects create frustrations in the lattice and result in a soft behavior, and mobile defects stabilize the polarization and produce a hard behavior. copyright 1997 Materials Research Society
[en] The Twymann-Green interferometry is applied to measure surface deformations of mechanical components in industrial areas with non-contact since it requires relatively simple optical arrangement. In this study, a tapered canti-lever beam was used to measure out-of-plane displacement by Twymann-Green interferometry. The surface of the specimen was polished to be shown as that of a mirror. Fringes observed from the specimen with a shiny surface include speckle noise and are similar to those obtained from the specimen sprayed by white paint. Gussian blur which is a commercial software is used to eliminate high frequency speckle noise. Phase shifted four fringes using PZT were captured and were used to calculated phased image. Experimental results of the tapered canti-levered plate analyzed by 4-step phase shifting method are close to the theoretical expectation.
[en] The parametric effects of a PZT beam that is simultaneously used as a vibration absorber and a power harvester were investigated in this study. A cantilever beam paved with PZT layers and with added tip mass has been widely used as a harvester or sometimes as a Dynamic vibration absorber (DVA). However, the beam is rarely considered a collocated device. In this study, the first step was theoretical derivation of a distributed beam covered with bimorph PZT layers. Then, the beam was attached to a 1DOF vibratory main system. Two indicators for vibration absorption and power harvesting were defined. Numerical results demonstrated that the lumped mass ratio favored both of the abilities, but that the DVA mass ratio influenced these two abilities in exactly the opposite way. The conjunction of a harvester circuit into a DVA shifted its resonance frequency up to 5 % (an extreme case of open circuit R→∞). Simultaneous power harvesting diminished the absorption capability up to 35 % for each set of mass ratios. To achieve the maximum degree of power harvesting, a corresponding load resistance that somewhat increases with the lumped mass ratio is applied. Experimental results verified the existence of the best load resistance, but the measured harvested curve was lower than the theoretical calculation because of structure damping and deviations of PZT material properties
[en] Effects of electric field-frequency, electric field-amplitude, mechanical stress, and temperature on the hysteresis area, especially the scaling form, were investigated in soft lead zirconate titanate (PZT) bulk ceramics. The hysteresis area was found to depend on the frequency and field-amplitude with the same set of exponents as the power-law scaling for both with and without stresses. The inclusion of stresses into the power-law was obtained in the form of < A-Aσ=0> ∝ f-0.25E0σ0.45 which indicates the difference in energy dissipation between the under-stress and stress-free conditions. The power-law temperature scaling relations were obtained for hysteresis area (A) and remanent polarization Pr, while the coercivity EC was found to scale linearly with temperature T. The three temperature scaling relations were also field-dependent. At fixed field amplitude E0, the scaling relations take the forms of < A> ∝ T-1.1024, Pr ∼T-1.2322 and (EC0 - EC) ∼T
[en] We describe the fabrication of lead zirconate titanate (PZT) nanodisc arrays isolated by a polymer layer and contacted with a top electrode. PZT thin films were deposited by multitarget sputtering onto a platinum/titanium bottom electrode and structured by means of nanosphere lithography. To guarantee short-circuit-free deposition of a top electrode, the space between the nanostructures was filled by a polymer. Two approaches for the filling are demonstrated: (a) imprinting and (b) skim coating. Single nanodiscs embedded in a flexible polymer matrix have two major advantages. First, taking into account the flexibility of the matrix, they can vibrate in lateral direction and, second, due to shrinking to the nanoscale, predominant directions of the polarization form, such as vortex- or bubble-like domain patterns. Piezoresponse force microscopy was performed on patterned and nonpatterned samples with and without a top electrode to check the local piezoresponse. Comparison of the different samples revealed an increase in lateral piezoactivity for patterned samples with Ni/Cr electrode while the out-of-plane piezoresponse remained constant. Gold electrodes limit the piezoresponse in both measured directions.
[en] Electric field and aging time are two important factors that affect the mechanical strength and long-term reliability of lead zirconate titanate or PZT actuators. In the present work, a commercial PZT-5A aged four years was examined using ball-on-ring (BoR) mechanical testing under coupled electric fields. The electric field range of −3Ec to +3Ec (Ec, coercive electric field) was studied (i.e., −3Ec, −Ec, 0, +Ec, +2Ec, and +3Ec) with a controlled electric loading path. A Weibull distribution was used to interpret the mechanical strength data. With an electric field preloaded from 0 to −3Ec, it was found that subsequent increases in the electric field resulted in an asymmetrical V-shaped curve of mechanical strength against the electric field. The bottom of the V curve was located near the zero electric field level. Microscopy analysis showed that pores were the strength limiter for the tested PZT under electromechanical loadings. (technical note)
[en] For high electrical loads, the electromechanical characteristics of PZT actuators are impacted by nonlinearities. This work presents a procedure, derived from nonlinear analysis, to assess separately the electrostriction and the elastostriction parameters of bulk PZT ceramics. A detailed investigation has shown that the electrostriction is dominant in actuator applications, while the elastostriction affects sensor applications. Further, the relationship between electrostriction and polarization in PZT material is discussed
[en] This paper describes the methods applied to the some chemical analysis of PZT ceramics during processing, and particularly in the finished ceramic, since small compositions changes can produce marked changes in final piezoelectric properties. Data on two samples (powder and high-fired ceramic material) are presented. The major constituents - Pb,Zr and Ti; nine trace elements and compound concentrations - Nb,C, Si, Al, Sr, free lead oxide, acid-insoluble matter, free oxygen and crystalline phases were determined using x-ray fluorescence, x-ray diffraction, thermal neutron activation, direct combustion, atomic absorption, vacuum fusion/gas chromatography, gravimetry, titrimetry and spectrophotometry. The major constituents were determined by more than one method, with good agreement between the various methods. (author)
[en] We investigate temperature hysteresis of magnetization in a two-layer composite structure composed of magnetocaloric and electrocaloric materials. The proposed model describes the simultaneous application of electric and magnetic fields. Such an approach allows analysing features of multicaloric effect in bilayer FeRh/PZT structure. To verify the correctness of the developed model, the theoretical results are compared with the experimental data for the multicaloric effect in the FeRh-PZT structure. (paper)