Uniaxial Compressive Stress Dependence of the High-Field Dielectric and Piezoelectric Performance of Soft PZT Piezoceram
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The influence of uniaxial prestress on dielectric and piezoelectric performance was studied for soft lead zirconate titanate piezoceramics. High electric field induced polarization and longitudinal/transverse strain were measured at different compression preload levels of up to −400 MPa. The parameters evaluated included polarization/strain outputs, dielectric permittivity, piezoelectric constants, and dissipation energy as a function of the mechanical preload and electric-field strength. The results indicate a significant enhancement of the dielectric and piezoelectric performance within a certain prestress loading range. At much higher stress levels, the predominant mechanical depolarization effect makes the material exhibit hardly any piezoeffect. However, the enhanced performance achieved by a small stress preload is accompanied by an unfavorable increased hysteresis, and consequently, increased energy loss, which is attributed to a larger extrinsic contribution due to more non-180° domain switching induced by the combined electromechanical load.
I. INTRODUCTION
Piezoelectric ceramics offer many excellent characteristics that are attractive to smart structure and system applications, such as large generative force, quick response time, low power consumption, and compactness.1,2 Since the discovery of lead zirconate titanate (PZT) ceramics about five decades ago, PZT and related modified families have become the most widely used and studied piezoelectric ceramics due to their outstandingly high electromechanical coupling coefficients. To obtain maximum energy conversion efficiencies, most of the technically important PZT ceramics are composed in the vicinity of the morphotropic phase boundary (MPB) with two ferroelectric phases (i.e., the tetragonal and the rhombohedral phase) coexisting inside the materials.3,4 Initially, piezoelectric materials were developed for high-frequency, small-signal loading applications, like buzzers, telephone diaphragms, surface acoustic wave filters, hydrophone and ultrasonic cleaners, and so forth.5,6 When a small stress (T) and a weak electric field (E) are applied to a piezoceramic specimen along its poling axis (3-direction), the resulting electric displacement (D) and strains (S) can be described by the linear constitutive relations
a)
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J. Mater. Res., Vol. 19, No. 3, Mar 2004 Downloaded: 11 Mar 2015
D3 = ⑀T33E3 + d33T3 S3 = d33E3 + sE33T3 S1 = S2 = d31E3 + sE13T3 ,
(1)
where the material’s parameters (constants) ⑀, d, and s given by the manufacturers are normally determined by weak-field measurements performed using a resonance– antiresonance method.7 Considerable efforts were made in recent years to use piezoelectric ceramics for low-frequency active actuator applications, some of the most promising industrial applications including precision positioning, bending actuators for automated weaver’s looms, active vibration suppression devices, noise controls, piezom
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