Zhongyan Meng

Microdisplacement characteristics and microstructures of functionally graded piezoelectric ceramic actuator

Abstract In this work, we report a functionally gradient piezoelectric ceramic actuator with sandwiched structure prepared by the powder metallurgical method. The functional gradients of piezoelectric activity and dielectric activity vary inversely across the thickness of the actuator. Such functional gradients are obtained by interdiffusion reaction between a high piezoelectric composition [Pb(Zr,Ti)O 3 /PZT] and a high dielectric composition (PbNi 1/3 Nb 2/3 O 3 /PNN). The bending displacement at the free end of the PNN/PZT functionally graded piezoelectric ceramic actuator was approximately 20 m when 1.4-kV/mm electric field was applied. The grain morphology and compositional distribution across the actuator section and the microstructures of the sandwiched layer were investigated by scanned electron microscopy equipped with energy-dispersive spectroscopy, transmission electron microscopy, and selected area electron diffraction patterns, respectively.

The influence of the morphotropic phase boundary on the dielectric and piezoelectric properties of the PNN-PZ-PT ternary system

The influence of the morphotropic phase boundary (MPB) on the dielectric and piezoelectric properties of PbNi1/3Nb2/3O3-PbZrO3-PbTiO3 (PNN-PZ-PT) ternary system were systematically investigated. The results showed that the piezoelectric constant d31 and plane coupling factor kp reached a maximum in the vicinity of morphotropic phase boundary. The highest value of the piezoelectric constant d31 was 260×10−12 C/N. The Curie temperature Tc decreased rapidly with increasing content of PNN. The lattice parameters a increased and c decreased with increasing PNN content and the Zr/Zr + Ti ratio as a result of the crystal structural transformation from tetragonal to rhombohedral phases.

Interdiffusion reaction in the PZT/PNN functionally gradient piezoelectric ceramic materials

The interfacial diffusion reaction between lead zirconate titanate (PZT) and lead nickel niobate (PbNi1/3Nb2/3O3:PNN) phases in the PZT/PNN functionally gradient piezoelectric ceramics were investigated as a function of the diffusion temperature and time, respectively. The ionic composition distribution profiles in the interdiffusion region were examined by electron probe microbeam analysis (EPMA). Based on a diffusion model of the overlapped diffusion solution from thin slab, the numerical simulation for the ionic composition distribution was carried out by computer, which was in agreement with the EPMA result. The diffusion coefficients for the Ni2+, Nb5+, Ti4+ and Zr4+ ions were determined, which were 33.8, 22.6, 10.8 and 9.9×10-12 m2 s-1, respectively. The apparent activation energies for these ions were 94.4, 171.7, 257.5 and 325.8 kJ mol-1, respectively. The differences in the ionic diffusion coefficients and apparent activation energies were discussed from the viewpoint of the crystal chemistry.

Dielectric and piezoelectric properties of Pb(Ni1/3Nb2/3)O3–PbTiO3–PbZrO3 ceramics modified with bismuth and zinc substitutions

The dielectric and piezoelectric properties of the (Pb0.985Bi0.01)(Ni1/4Zn1/12Nb2/3)x- (ZrσTi1-σ)1-xO3 piezoelectric ceramic system (0.2 ≤ x ≤ 0.7, 0.1 ≤ σ ≤ 0.9) were systematically investigated. The results showed that, after poling, the dielectric constant, ε33T, increased for the tetragonal compositions but decreased for the rhombohedral compositions. Furthermore, high values of ε33T and piezoelectric modulus, d31 were found for the compositions along the extension of the morphotropic phase boundary. The highest values of the planar electromechanical coupling factor, Kp, and the piezoelectric modulus, d31, were found to be 0.70 and − 274 × 10-12 C N-1, respectively. The Curie temperature, remanent polarization, coercive field and the lattice constants of the a and c axes in relation to the Pb(Ni1/3Nb2/3)O3 content and the Zr/Zr + Ti ratio were also determined.

Domain morphology evolution associated with the relaxor–normal ferroelectric transition in the Bi- and Zn-modified Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 system☆

Abstract To understand the dielectric behavior from a viewpoint of domain configuration, the domain morphology evolution in (Pb0.985Bi0.01)(Ni1/4Zn1/12Nb2/3)0.2(Zr1-σTiσ)0.8O3 ceramics (0.30⩽σ⩽0.60) has been investigated by transmission electron microscopy and high resolution electron microscopy. The results indicated that the domain morphology evolved from the normal micron-sized domains to herringbone domain patterns, and finally to the polar nanodoamains approximately 3∼6 nm in size when the PT content was decreased from 60 to 30 mol%. The normal twin-related 90° macrodomains are closely correlated with the normal dielectric response of the composition with higher PT content, whereas the relaxor response of the composition with lower PT content is directly attributable to nanometer domains that contain 1:1 short-range ordering on the B-site sub-lattice. A model is proposed to describe the effect of the PbTiO3 content on the ferroelectric domain morphology evolution in the system.

Effect of the interdiffusion reaction on the compatibility in PZT/PNN functionally gradient piezoelectric materials

The interfacial diffusion reaction Pb(Ni/sub 1/3/Nb/sub 2/3/)O/sub 3/ (PNN) and Pb(Zr,Ti)O/sub 3/ in functionally gradient materials (FGM) has been investigated as a function of sintering temperature and time, respectively. The compositional distribution profiles of the interaction region were examined by electron probe microbeam analysis (EPMA). According to the diffusion model, the concentration distribution profiles were simulated by way of numerical approaches. The diffusivity and activation energy for Ni/sup 2+/, Nb/sup 5+/, Ti/sup 4+/ and Zr/sup 4+/ ions have been estimated. The results were discussed.

EPMA and TEM investigations on the interdiffusion layer of the PNN/PZT functionally gradient piezoelectric ceramics

The compositional profile, distribution of the phases and the ordering behavior in the interdiffusion layer of the PNN/PZT functionally gradient piezoelectric ceramics have been investigated by electron probe microbeam analyses (EPMA) and transmission electron microscopy (TEM) respectively. The results show that the thickness of the interdiffusion layers (d) for Ni2+, Nb5+, Ti4+ and Zr4+ ions are ordered as dNi2+ > dNb5+ > dTi4+ > dZr4+. It is demonstrated by TEM observation and selected area electron diffraction (SAED) patterns that a clear interface between the rhombohedral and pseudocubic phases exists in the interdiffusion layer. The SAED studies also reveal the presence of F spots along the [111] direction of the perovskite cubic unit cell. The origin of this superstructure is determined.

Actuators, piezoelectric ceramics and functionally gradient materials

Abstract Piezoelectric ceramic actuators and materials play a key role in the development of advanced precision engineering. The breakthroughs in this field are closely related to the development of various types of piezoelectric ceramic actuators and related materials. The likelihood that the range of applications and demand for actuators will grow quickly has stimulated intensive researches on piezoelectric ceramics. Functionally gradient materials (FGMs) are new classes of composites characterized by compositional and/or microstructural gradation over macroscopic/microscopic distances. This constitutional gradation can be tailored to meet specific needs while providing the best utilization of composite components. Furthermore, FGMs technology is also a novel interfacial technology to solve the problems associated with the sharp interface between two dissimilar materials. In recent years significant advances in the development of FGMs have been achieved. In this paper, we first briefly review the recent progress of ceramic actuators and developments of piezoelectric materials, and then focus on summarizing typical applications of functional gradients in piezoelectric and ferroelectric materials.

Configurations of ferroelectric domains in bismuth- and Zinc-modified Pb(Ni_1/3Nb_2/3)O_3-PbTiO_3-PbZrO_3 ceramics

Transmission electron microscopy was used to investigate the domain structures of the (Pb0.985Bi0.01)(Ni1/4Zn1/12Nb2/3)0.2(Zr_σTi1-σ)0.8O3 (0.30 ≤ σ ≤ 0.70) ceramics, which are located in the ferroelectric tetragonal and rhombohedral phase regions, and also near the morphotropic phase boundary (MPB). The results show that the lamellar twinning domains and the δ-fringe contrast are most frequently observed in the compositions located in the ferroelectrc tetragonal phase region. In the compositions near the MPB, a banded domain structure similar to herringbone pattern is observed, which contains many parallel bands forming 90° or 70° angles whereas they are inconsistent with one another on both sides of the herringbone domain patterns. The morphology of the herringbone domain structure observed in the bismuth- and zinc-modified PNN-PZ-PT ceramics with composition near the MPB can be described by a space-stacking succession of two crystallographically equivalent plates whereas made from different twin-related domains, with the same habit plane parallel to the (011)-type plane. In the compositions located in the rhombohedral phase region, the stripelike domains are observed, and a local random contrast representing short-range-ordered ‘island’-typed polar clusters or nanodomains is also found, which is attributed to the existence of the polar microregions with the dispersed nanometer-sized short-range-ordered domains in the rhombohedral matrix, because the free energy of the ensembl e of the polar microregion is lowered, and the relative thermodynamic stability is increased with increasing the content ratio of Zr to Ti. In addition, the wavy character in the thickness fringe is commonly observed at the fringe of thin foil, which is due to continuous bending of the thin foil at various equivalent directions.