Search

This work demonstrates the potential of porous BaTiO3for piezoelectric sensor and energy-harvesting applications by manufacture of materials, detailed characterisation and application of new models. Ferroelectric macro-porous BaTiO3ceramics for piezoelectric applications are manufactured for a range of relative densities,α = 0.30–0.95, using the burned out polymer spheres method. The piezoelectric activity and relevant parameters for specific applications are interpreted by developing two models: a model of a 3–0 composite and a ‘composite in composite’ model. The appropriate ranges of relative density for the application of these models to accurately predict piezoelectric properties are examined. The two models are extended to take into account the effect of 90° domain-wall mobility within ceramic grains on the piezoelectric coefficients. It is shown that porous ferroelectrics provide a novel route to form materials with large piezoelectric anisotropyat 0.20 ≤α≤ 0.45 and achieve a high squared figure of merit. The modelling approach allows a detailed analysis of the relationships between the properties of the monolithic and porous materials for the design of porous structures with optimum properties. [ABSTRACT FROM PUBLISHER]

The structure of a novel 1–3-type composite is put forward. It consists of a system of poled ferroelectric ceramic rods surrounded by a ceramic/polymer matrix. The effect of the anisotropy of elastic moduli of the 0–3 matrix on piezoelectric sensitivity and hydrostatic response of the 1–0–3 composite is first analysed. Effective parameters are predicted and analysed for novel composites based on ferroelectric PCR-7M ceramic (PZT type). Examples of significant piezoelectric sensitivity (g*33 ≈ 400 mV·m/N, g* h ≈ 200 mV·m/N), hydrostatic piezoelectric activity (d* h ≈ 350 pC/N) and electromechanical coupling (k* h ≈ 0.45) are discussed. [ABSTRACT FROM PUBLISHER]

The structure of a high-sensitivity 1–3-type composite is studied. The effect of the anisotropy of elastic moduli of the 0–3 matrix on piezoelectric sensitivity, hydrostatic piezoelectric coefficient and anisotropy of electromechanical coupling factors is analysed. Effective parameters are predicted and analysed for the 1–0–3 composite based on modified lead titanate ceramic. The large values of piezoelectric coefficients g*33 ≈ 400 mV.m/N and g* h ≈ 200 mV.m/N and the considerable anisotropy of electromechanical coupling factors (k*33/k*31 ≈ –15, k* t /k* p ≈ –9) of the studied composite are discussed. [ABSTRACT FROM AUTHOR]

Effective piezoelectric coefficients e33*, d33*, g33*, and h33*, squared figures of merit d33*g33* and dh*gh*, and other related parameters of novel 0-3 and 0-3-0 composites based on single crystals of relaxor-ferroelectric solid solutions of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 are studied using the effective field method, effective medium method and finite element method. The volume-fraction dependences of a number of parameters and figures of merit are determined using the above methods and compared for composites with aligned prolate spheroidal inclusions. Four parameter ratios that determine interconnections between the effective electromechanical constants of the 0-3-type composites are first introduced. These parameter ratios are used to interpret the longitudinal dielectric and piezoelectric response of composite structures with prolate inclusions that exhibit high piezoelectric activity. The role of piezoelectric anisotropy and activity of the composite components in forming the longitudinal piezoelectric effect is analysed. Specific novel composite architectures with high piezoelectric sensitivity (longitudinal and hydrostatic) are identified and discussed. [ABSTRACT FROM AUTHOR]

The effect of the polarisation orientation of [011]-poled polydomain PMN-0.29PT single crystal on the hydrostatic piezoelectric coefficients [image omitted] and [image omitted] of a parallel-connected 2-2 composite has been analysed. Orientation and volume-fraction dependences of the piezoelectric coefficients of the 2-2 PMN-0.29PT/polymer composite have been studied to determine extreme points of [image omitted] and [image omitted] in three cases of rotations of the main crystallographic axes of the PMN-0.29PT single crystal. The largest values of the hydrostatic piezoelectric coefficients [image omitted] = 444 pC/N and [image omitted] = 33.1 C/m2 are of interest for hydroacoustic applications. Important contributions from the piezoelectric coefficients [image omitted] and [image omitted] into [image omitted] and [image omitted], respectively, have been determined near the extreme points of the hydrostatic parameters. [ABSTRACT FROM AUTHOR]

This paper considers effective electromechanical properties of the relaxor-ferroelectric crystal/polymer composite with 2-2 connectivity. A single-domain 0.67Pb(Mg1/3Nb2/3)O3—0.33PbTiO3 crystal/polymer composite is proposed in which the polarisation vectors of components are tailored to optimise the electromechanical coupling factors k*3j and k*h. A strong correlation between the hydrostatic electromechanical coupling factor k*h and the hydrostatic piezoelectric coefficient d*h is observed near min k*h and max k*h. Examples of the condition k*31=k*32 are also considered. The specific advantages and potential of the 2-2 composite in terms of its considerable d*h and k*h values are discussed in connection with the studied orientation effect. [ABSTRACT FROM AUTHOR]

This paper studies polarisation orientation effects in 1-3 composites with two piezo-active components. It is shown how the orientation of the main crystallographic axes in 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 single-crystal rods and the poling direction of a polyvinylidene fluoride matrix affect the volume fraction behaviour of the piezoelectric coefficients, squared figure of merit and hydrostatic parameters of the composites. For a fixed orientation, effective parameters calculated using the matrix approach are compared with those evaluated by the finite element method. Possible property advantages concerned with orientation effects, maxima of effective parameters and high performance of these composites are analysed taking into consideration the electromechanical properties of the components. [ABSTRACT FROM AUTHOR]

This paper is devoted to the analysis of effective electromechanical properties and their maxima in 0-3-type composites based on (1 - x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3 single crystals. It is shown that the electromechanical interaction between the single-crystal and polymer components with the anisotropy of their piezoelectric coefficients e33(n)/|e31(n)| ≥ 5 results in relations d33* ≈ e33*s33*E, g33* ≈ h33*s33*D, and kt* ≈ k33* for the electromechanical constants. These relations hold in a wide range of volume fraction and aspect ratio of the spheroidal inclusions in the 0-3 composite. An increase in the maximum values of different effective parameters is expected by forming a system of oblate air pores in the matrix. [ABSTRACT FROM AUTHOR]