Piezoelectric sensitivity and hydrostatic response of novel lead-free 2–0–2 composites with two single-crystal components

This paper reports the piezoelectric performance and important related hydrostatic parameters of 2–0–2 composites based on lead-free ferroelectric and piezoelectric single crystals with 4mm symmetry. We demonstrate that ferroelectric domain-engineered alkali niobate-tantalate based single crystals provide large values of the piezoelectric coefficients g3j ∗ and related parameters when used in a 2–0–2 composite system with a relatively wide range of volume fractions of single-crystal components. An ‘aspect-ratio effect’ as a result of the presence of inclusions of a piezoelectric Li2B4O7 single crystal in a polymer medium is studied for the first time for a case where the elastic compliance s12 in the single crystal/polymer layer of the composite passes through zero. It is observed that changes in the aspect ratio and volume fraction of the Li2B4O7 inclusions influence the hydrostatic piezoelectric coefficient gh ∗, squared figure of merit dh ∗gh ∗ and electromechanical coupling factor kh ∗ of the composite, and large values of gh ∗∼102 mV·m/N, dh ∗gh ∗∼ (10−11–10−10) Pa−1 and kh ∗≈ 0.6–0.7 are achieved. A link between max kh ∗ and a change in sgns12 is first described for the 2–2-type composite, and a comparison of the hydrostatic parameters of the novel and related composites is made. The present results show the potential of lead-free 2–0–2 composites that are suitable for piezoelectric sensor, energy-harvesting and hydroacoustic applications.</p

Relationships between piezoelectric and energy-harvesting characteristics of 1–2–2 composites based on domain-engineered single crystals

The paper reports on the piezoelectric performance, electromechanical coupling and related energy-harvesting figures of merit of three forms of 1–2–2 composites based on domain-engineered single crystals. The effect of the single-crystal piezoelectric properties and elastic properties of the laminar polymer matrix on the appropriate figures of merit of the composite is studied. The main active components of the studied composites are [0 0 1]-poled perovskite-type single crystals with chemical compositions: 0.92Pb(Zn1/3Nb2/3)O3–0.08PbTiO3, 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 and [Li x (K1−y Na y)1−x ](Nb1−z Ta z)O3: Mn, where x = 0.06, y = 0.1–0.3, z = 0.07–0.17, and the level of Mn doping is 0.25 mol. %. Examples of non-monotonic volume-fraction dependences of the piezoelectric properties, figures of merit and anisotropy factors are analysed. New diagrams are first built to demonstrate the volume-fraction regions where a large anisotropy of the piezoelectric coefficients d 3j * and electromechanical coupling factors k 3j * is achieved, and where energy-harvesting figures of merit of the composite are at least five times larger than analogous parameters of single-crystal components. The studied 1–2–2 composites are of interest as anisotropic materials with high piezoelectric sensitivity and large figures of merit which are important for sensor, energy-harvesting and related applications.</p

Electromechanical Coupling Factors of Novel 0-3-0 Composites Based on PMN-xPT Single Crystals

This paper is devoted to the problem of the electromechanical coupling of advanced Single crystals (SCs) of relaxor-ferroelectric solid solutions of with perovskite-type structure are of interest as highly effective components of advanced piezo-active composites. Electromechanical coupling is one of the main characteristics of any piezoelectric media, including composites with the piezo-active components. Recent results on the laminar [1, 2], matrix cellular [3] and fibrous [4] composites based on PMN-0.33PT SCs demonstrate the key role of the piezoelectric coefficients d ij of SC in achieving considerable electromechanical coupling in these composites. Particular features of the behaviour of the electromechanical coupling factors (ECFs) in the 0-3 PMN-xPT SC/ polymer composites were discussed in work The determination of the effective electromechanical properties of the 0-3-0 composit

Remarkable hydrostatic piezoelectric response of novel 2–0–2 composites

This is the first study of the significant influence of the 0–3 ceramic / polymer layer on the hydrostatic piezoelectric parameters of novel 2–0–2 relaxor-ferroelectric single crystal / ferroelectric ceramic / polymer composites. Examples of the performance of two 2–0–2 composites based on domain-engineered single crystals are analysed by taking into account the elastic anisotropy of the 0–3 ceramic/polymer layers with changes in the volume fraction of ceramic inclusions and their aspect ratio. The unique feature of the hydrostatic properties of the studied 2–0–2 composites consists in their large values of piezoelectric coefficients d*h ≈ 1 nC/N and e*h ≈ 20 C/m2, squared figure of merit d*hg*h∼ 10−10 Pa−1, and electromechanical coupling factor k*h ≈ 0.7.</p