Piezoceramic Matrix Research Articles

Dielectric percolation in ceramic matrix composites

This paper presents the results of an experimental study of the percolation behavior of the complex dielectric constant of ceramic matrix composites (CMC). Samples of piezoactive CMC were obtained by joint sintering of synthesized PZT piezoceramic powder (matrix) and crushed particles of sintered PZT piezoceramics (filler) of different compositions. The experimental dependencies of real and imaginary parts of the complex dielectric constant of CMC on the porosity of piezoceramic matrix and volume content of ceramic filler particles were measured and analyzed. It was shown that the additional porosity of the ceramic matrix resulting from sintering of the CMC masks the dielectric percolation transition, that actually occurs at the volume concentration of ceramic filler close to percolation threshold (V ∼ 1/3).

Ceramic matrix piezocomposites: microstructural features and dielectric properties

A new method for the fabrication of ceramic-matrix piezocomposites (CMC) ceramics/ceramics has been developed. Samples of piezoactive PZT/PZT composites with a mass concentration of components from 0 to 50% have been obtained. The study of microstructural and gravimetric features, as well as the dielectric properties of CMC, has been carried out. Finite element modeling and experimental study of CMC properties in the region of dielectric percolation transition have been performed. It is shown that the developed method for manufacturing CMC provides the formation of microhomogeneous composite structures with a uniform distribution of ceramic filler particles in a microporous piezoceramic matrix without the formation of transition regions and additional crystalline phases.

Determination of effective properties of porous piezoelectric composite with partially randomly metalized pore boundaries using finite element method

In this study, we investigate the effective characteristics of a porous piezocomposite with randomly distributed pores of arbitrary size and with partly metalized pore boundaries. Using the ANSYS APDL finite element software, we created a novel random representative volume element (RVE), applied the finite element approach to solve boundary value problems of homogenization, and calculated equivalent properties using the Hill–Mandel principle. The results demonstrate that when large random RVE and an appropriate finite element mesh are used, the porous piezocomposite with randomly metalized porosity borders will have the same crystal symmetry as the piezoceramic matrix. Therefore, when there is a significant material contrast between the various phases, a large random RVE is preferred in the modeling of particulate-filled composites. Furthermore, when the areas of metalized surfaces increase, the performance of the investigated composite in transverse sensing and actuation applications improves.

Ceramic matrix piezocomposites: method of fabrication and microstructure peculiarities

In the present work, we have developed a new method for the fabrication of piezoactive ceramic matrix composites (CMC) ceramics/ceramics. Samples of piezoactive PZT/PZT composites with a mass concentration of components from 0% to 60% have been obtained. A study of microstructural features, as well as a gravimetric analysis of CMC, has been carried out. It has been shown that the developed method for CMC manufacturing provides the formation of microhomogeneous composite structures with a uniform distribution of ceramic filler particles in a microporous piezoceramic matrix without the formation of transition regions and additional crystalline phases.

Comprehensive numerical characterization of a piezoelectric composite with hollow metallic inclusions using an adaptable random representative volume

This paper investigates a piezoelectric composite made up of a piezoceramic matrix with irregularly scattered random-sized hollow metal inclusions. This composite can be produced using a combination of porous ceramic fabrication methods and microcapsule transfer techniques that were previously utilized to deliver nanoparticle medicines in biomedical applications. The effective material characteristics were computed using a numerical homogenization methodology that included finite element analysis, random representative volume element, perfect contact between distinct phases, special linear boundary conditions, and the Hill–Mandel principle. To imitate the random distribution of inclusions inside a particle-filled composite, the relationship describing the inclusion’s volume fraction was adjusted by adding a regularity coefficient. Thus, a new representative volume was designed to study the effect of the non-uniform distribution of randomly sized inclusions on the effective coefficients of the composite. An analysis of the effective properties of this new composite system with metalized pores surfaces (SMPS) revealed the following features. Due to the presence of metallic impurities, the resulting electric induction field or mechanical stress field inside the piezoelectric phase is scattered, which raises the transverse piezoelectric moduli with the increase of the inclusion’s volume fraction. Also, the electrical permittivity coefficients increase steadily with the increase in the portion of the metallic impurities. According to the findings, the volume fraction of the inclusion can be considered the most critical parameter to modify the electromechanical characteristics of the SMPS. The effects of the regularity coefficient on the equivalent properties increase as the inclusion’s volume fraction increases. The effective dielectric constants decrease as the degree of regularity of the composite structure grows, increasing the effectiveness of the piezoelectric transducer in transverse energy harvesting and motor applications. The findings of the newly constructed representative volume were verified using a basic periodic unit-cell and a random representative volume based on the random sequential adsorption (RSA) method. The developed structure of the representative volume can be applied to simulate a wide range of composites in the form of solid particles. Piezoelectric transducers constructed from the proposed piezocomposite are predicted to function well in piezoelectric motors and transverse piezoelectric sensors.

Computer Simulation of Composites Consisting of Piezoceramic Matrix with Metal Inclusions and Pores

Computer Simulation of Composites Consisting of Piezoceramic Matrix with Metal Inclusions and Pores

About anomalous properties of porous piezoceramic materials with metalized or rigid surfaces of pores

The electromechanical properties of piezoelectric materials can be modified for some specific applications, e.g., hydrophone sensing applications, by incorporating a controlled porosity into them. This work investigates the effective moduli of a newly developed piezoelectric composite, fabricated using a novel approach, in which micro-and nanoparticles of specific metals or stiffer polymers were added to pore-forming agents and transported into ceramic matrices. This technique results in a porous piezocomposite with a metalized pore boundary. According to Newnham’s classification, it is a three-phase piezocomposite with connectivity 3–0–0. We considered a simple unit cell model composing of a cube of the piezoceramic material with a compound spherical pore at its center. The compound pore consists of a spherical vacuum pore and a spherical layer on its boundary. The spherical layer models the material deposited at the interface between the piezoceramic matrix and the pore. Based on the characteristics of this spherical layer, we studied porous piezocomposite with mechanically weak electrically conductive, mechanically hard dielectric, and mechanically hard electrically conductive pore surface. We assumed that this spherical layer is filled with a piezoelectric material. Very high dielectric permittivity moduli simulate the electrical conductivity, very high elastic stiffness moduli modulate the mechanical rigidity, while the piezoelectric moduli are negligible. We developed specific algorithms in ANSYS APDL to calculate the effective moduli of different composites understudy using the finite element method and the theory of effective moduli, considering the Hill–Mandel principle for energy conservation, under certain essential boundary conditions. Our simple unit cell model used for the main calculations was analogous to the model of the corresponding periodic composite. The findings of this basic model were also compared to a more complicated 3–0 random porosity composite model. We confirmed that the effective moduli versus porosity trends in both models are similar. We verified the numerical expectations by studying analytically the homogenization problem of an isotropic dielectric composite. The findings of this work confirm that the effective moduli of the developed piezocomposites significantly depend on the characteristics of material deposited between the piezoceramic and pore phases. The results of this study suggest that there may be several functional applications for these new piezocomposites.

Numerical investigation of the effects of partial metallization at the pore surface on the effective properties of a porous piezoceramic composite

This paper presents a numerical homogenization analysis of a porous piezoelectric composite with a partially metalized pore surface. The metal layers can be added to the pore surfaces to improve the mechanical and electromechanical properties of ordinary porous piezocomposites. Physically, constructing that composite with completely metalized pore surfaces is a challenging process, and imperfect metallization is more expected. Here, we investigate the effects of possible incomplete metallization of pore surfaces on the composite’s equivalent properties. We applied the effective moduli theory, which was developed for the piezoelectric medium based on the Hill–Mandel principle, and the finite element method to compute the effective moduli of the considered composites. Using specific algorithms and programs in the ANSYS APDL programming language, we constructed the representative unit cell element models and performed various computational experiments. Due to the presence of metal inclusion, we found that the dielectric and piezoelectric properties of the considered composites differ dramatically from the corresponding properties of the ordinary porous piezocomposites. The results of this work showed that piezocomposites with partially metallized pore surfaces can have a higher anisotropy, compared to the pure piezoceramic matrix, due to the defects in metal coatings.

Study of microstructure and electromechanical properties of ceramic-matrix piezocomposites PZT/α-Al2O3

The electromechanical properties and microstructural features of ceramic-matrix piezocomposites PZT/α-Al2O3 with different volume fractions of microcrystalline α-Al2O3 filler were studied. The concentration dependences of the complex elastic and electromechanical parameters of piezoelectric elements on α-Al2O3 microcrystals concentration were measured. It was found that, along with the influence of the non-piezoelectric phase α-Al2O3, the microporosity of the piezoceramic matrix appearing during sintering plays a decisive role in the formation of the electro-physical properties of ceramic-matrix piezocomposites PZT/α-Al2O3.

Microstructural features and electromechanical characteristics of ceramic-matrix piezocomposites

In this work, we studied elastic and electromechanical characteristics and microstructural features of piezoactive ceramic-matrix composites PZT/LiNbO3 with a volume fraction of microcrystalline LiNbO3 filler from 0 to 15 vol. %. The dependences of the complex elastic and electromechanical parameters of composite piezoelectric elements on LiNbO3 microcrystals concentration were measured. It was found that in the formation of the electrophysical properties of ceramic-matrix composites PZT/LiNbO3, the microporosity of the piezoceramic matrix appearing during the composite sintering played a decisive role.

Numerical analysis of the effective properties of inhomogeneously polarized porous piezoelectric ceramics with ni-doped pore walls taking into account the influence of volume fractions of metal and pores

The paper considers a porous piezoelectric composite with metal layers deposited on the interface between the piezoelectric and vacuum phases. Such metal layers can be added technologically to improve the mechanical and electromechanical properties of the composite. To find the effective moduli, we designed a simple representative cubic volume of a unit cell consisting of a piezoelectric matrix with a compound spherical pore in its center. In turn, the compound pore includes the pore itself and a hollow metal sphere on its surface. The composite's three phases were all modeled as piezoelectric materials. The conducting interface layer was modeled as a piezoelectric material with very high dielectric constants, small piezoelectric moduli, and elastic properties of the employed metal, while the vacuum pore was modeled as a piezoelectric material with marginal moduli. The mathematical formulation of boundary value homogenization problems with full contact conditions on the interface boundaries, based on the Hill energy criterion, was described. By solving nine boundary value problems of electroelasticity with different boundary conditions for displacements and electric potential by the finite element method, a complete set of effective moduli of the piezoelectric composite is determined. The importance of considering the inhomogeneous polarization due to the presence of pores and metallic inclusions was discussed. An approximate method was proposed for determining the inhomogeneous polarization field in a piezoceramic matrix, based on a preliminary solution of the electrostatic problem for dielectrics and locating the element coordinate systems rotated along the polarization vector. The paper describes the results of computational experiments for a piezocomposite consisting of PZT-5H piezoceramic matrix, pores, and nickel layers on the pore surfaces. Comparisons between the effective properties of this composite with different volume fractions of metal and the conventional porous piezocomposite were provided, depending on the porosity and taking into account the inhomogeneous polarization. Significant differences were observed for some piezomoduli and dielectric constants, which are promising for various practical applications of the considered composites in piezoactuators using the phenomenon of the transverse piezoelectric effect.

Effective properties of a porous inhomogeneously polarized by direction piezoceramic material with full metalized pore boundaries: Finite element analysis

This paper concerns the homogenization problems for porous piezocomposites with infinitely thin metalized pore surfaces. To determine the effective properties, we used the effective moduli method and the finite element approaches, realized in the ANSYS package. As a simple model of the representative volume, we applied a unit cell of porous piezoceramic material in the form of a cube with one spherical pore. We modeled metallization by introducing an additional layer of material with very large permittivity coefficients along the pore boundary. Then we simulated the nonuniform polarization field around the pore. For taking this effect into account, we previously solved the electrostatic problem for a porous dielectric material with the same geometric structure. From this problem, we obtained the polarization field in the porous piezomaterial; after that, we modified the material properties of the finite elements from dielectric to piezoelectric with element coordinate systems whose corresponding axes rotated along the polarization vectors. As a result, we obtained the porous unit cell of an inhomogeneously polarized piezoceramic matrix. From the solutions of these homogenization problems, we observed that the examined porous piezoceramics composite with metalized pore boundaries has more extensive effective transverse and shear piezomoduli, and effective dielectric constants compared to the conventional porous piezoceramics. The analysis also showed that the effect of the polarization field inhomogeneity is insignificant on the ordinary porous piezoceramics; however, it is more significant on the porous piezoceramics with metalized pore surfaces.

Dynamic interaction of a thin metallic inclusion with a piezoceramic matrix

A mathematical model of dynamic behavior of a thin metallic inclusion or a layer in a piezoelectric medium subjected to longitudinal shear load is constructed. At the boundary of inclusion and matrix, the conditions of perfect mechanical contact and zero electric potential are prescribed. Modeling is performed using the apparatus of the theory of singular perturbations. Cite as: Yu. I. Maksymiv, Yu. V. Porokhovsky, R. V. Rabosh, V. O. Mishchenko, Ya. I. Kunets, “Dynamic interaction of a thin metallic inclusion with a piezoceramic matrix,” Prykl. Probl. Mekh. Mat. , Issue 17, 134–138 (2019) (in Ukrainian), https://doi.org/10.15407/apmm2019.17.134-138

Analysis of porosity influence on the effective moduli of ceramic matrix PZT composite using the simplified finite element model

The problem of determining the effective moduli of a ceramic matrix piezocomposite with respect to multiscale porosity was considered. To solve the homogenization problem, the method of effective moduli in the standard formulation, the finite element method and the ANSYS computational package were used. Various models of two-phase and three-phase composites consisting of a piezoceramic matrix, elastic inclusions of corundum and pores of various sizes have been investigated. Finite element models of representative volumes of 3–0 and 3–0–0 connectivities were developed. The results of computational experiments showed that effective moduli depend quite significantly not only on the volume fractions of inclusions and pores, but also on the structure and size of pores in comparison with the characteristic sizes of inclusions.

A new piezoelectric hollow cylindrical transducer with multiple concentric annular metal fillers

Previous studies have proved that adding proper metal fillers into piezoceramics can enhance their mechanical and dielectric properties. This work will examine a new multiple concentric annular metal filling style in a short piezoelectric hollow cylindrical transducer, and study its radial vibration characteristics. A theoretical model formulated from plane stress condition is proposed to describe this type of transducers, and the reliability of this model is verified by the finite element simulation results. Furthermore, the effects of the important parameters including number, material types and thickness of the filler on the electromechanical characteristics of the transducer are investigated. The results indicate that the metal fillers with greater sound velocity ratio compared with the piezoceramic matrix can increase the fundamental resonance and anti-resonance frequencies. The metal fillers with smaller Young’s modulus can achieve the greater fundamental electromechanical coupling coefficient. These findings obtained are very beneficial for improving the design of piezoelectric cylindrical ultrasonic and underwater sound transducers.

Microstructural Features and Electrophysical Characteristics of Ceramic–Crystal Matrix Composites

The electrophysical properties of ceramic–crystal matrix composites are studied. Piezoelectrically active PZT/LiNbO3 ceramic matrix composites with LiNbO3 concentrations of 0–20 vol % are fabricated. Complex elastic, dielectric, and piezoelectric parameters are measured, and the microstructural characteristics of the obtained samples are studied experimentally. It is found that the extreme electrophysical properties of ceramic–crystal matrix composites depend on the properties and structure of the piezoceramic matrix and crystalline filler, and on the matrix microporosity produced during sintering. The electrophysical parameters of ceramic–crystal matrix composites as functions of crystalline filler content are established through the competing microporosity growth effects of the ceramic matrix and the increase in crystalline filler content.

Finite element simulation of effective properties of microporous piezoceramic material with metallized pore surfaces

ABSTRACTThe paper presents a computer design of effective properties of microporous piezoceramic materials with fully metallized pore surfaces based on the simulation of the representative volume structure, the effective moduli method of the composite mechanics, and the finite element method. ANSYS finite element software was used to obtain numerical solution of the homogenization problems. To simulate the metallization on the boundaries of pores with piezoceramic matrix, the boundary conditions of free electrodes and elastic shell finite elements were used. The influence of the pore surface metallization on the values of effective moduli for microporous piezoceramics PZT-4 was investigated numerically.

Nanoparticles Transport in Ceramic Matriсes: A Novel Approach for Ceramic Matrix Composites Fabrication

The results of practical implementation of a new method for porous piezoceramics, and ceramic matrix piezocomposites fabrication were presented. The method was based on nanoparticles transport in ceramic matrices using a polymer nanogranules coated or filled with a various chemicals, with successive porous ceramics fabrication processes. Different types of polymer microgranules filled and coated by metal-containing nanoparticles were used for a pilot samples fabrication. Polymer microgranules were examined using transmission and scanning electron microscopy as well as by EXAFS and X-ray emission spectroscopy. Pilot samples of nano- and microporous ceramics and composites were fabricated using different piezoceramics compositions (PZT, lead potassium niobate and lead titanate) as a ceramic matrix bases. Resulting ceramic matrix piezocomposites were composed by super lattices of closed or open pores filled or coated by nanoparticles of metals, oxides, ferromagnetics etc. embedded in piezoceramic matrix. Dielectric and piezoelectric parameters of pilot samples were measured using piezoelectric resonance analysis method. New family of nano- and microporous piezoceramics and ceramic matrix piezocomposites are characterized by a unique spectrum of the electrophysical properties unachievable for standard PZT ceramic compositions and fabrication methods.

Reliability enhancement in nickel-particle-dispersed alkaline niobate piezoelectric composites and actuators

Piezoceramics and related devices are naturally fragile. Here we have produced piezoelectric composites of Ni-particle-dispersed Li-doped (K,Na)NbO3 (LKNN/Ni), and used these composites to make actuators with functionally graded microstructure (FGM). The mechanical properties of the LKNN/Ni composites were greatly enhanced by the incorporation of Ni particles. An LKNN–20%Ni composite exhibited double the fracture toughness of the monolithic LKNN ceramic. An LKNN/Ni piezoelectric FGM actuator subjected to a large number of cycles of electrical loading still maintained acceptable driven performance. The enhancement of reliability in the LKNN/Ni composites and actuators is attributed to the uniformly dispersed Ni particles in the piezoceramic matrix. Deformation of these Ni particles absorbs the energy of crack propagation and thus greatly strengthens the composites and devices. These new FGMs contribute further to the reliability enhancement of piezoelectric actuators.

A single-walled carbon nanotube reinforced 1–3 piezoelectric composite for active control ofsmart structures

We propose a new 1–3 piezoelectric composite comprised of armchair single-walled carbonnanotubes imbedded in a piezoceramic matrix which we call a NRPEC (nanotubereinforced 1–3 piezoelectric composite). Values of effective piezoelectric and elastic moduliof the NRPEC determined through a micromechanical analysis are found to be significantlyhigher than those of the 1–3 piezoelectric composite comprised of piezoelectric fibersimbedded in an epoxy matrix. The performance of the NPREC as a constraining layer inan active constrained layer damping (ACLD) treatment of a laminated composite beamhas been studied by the finite element method. Both in-plane and out-of-planeactuations by the constraining layer of the ACLD treatment have been considered, andits length has been optimized by implementing a controllability criterion. Thecomputed controllability measure and the frequency response reveal that the proposedconstraining layer performs better than the 1–3 piezoelectric/epoxy composite layer.