J. R. Giniewicz

Composite Piezoelectric Sensors

A hydrophone is an underwater microphone or transducer used to detect underwater sound. The sensitivity of a hydrophone is determined by the voltage that is produced by a hydrostatic pressure wave. The hydrostatic voltage coefficient, gh, relates the electric field appearing across a transducer to the applied hydrostatic stress, and is therefore a useful parameter for evaluating piezoelectric materials for use in hydrophones. Another piezoelectric coefficient frequently used is the hydrostatic strain coefficient, dh, which describes the polarization resulting from a change in hydrostatic stress. The gh coefficient is related to the dh coefficient by the relative permittivity (K): gh = dh/ɛoK, where ɛo is the permittivity of free space.

Pyroelectric response and depolarization behavior of (1−x)Pb(Sc1/2Ta1/2)O3-(x)PbTiO3 materials

Abstract The pyroelectric response of selected compositions from this solid solution system have been investigated. The nature of the temperature dependence of the pyroelectric coefficient for the compositions examined indicate the presence of a relatively broad, curved morphotropic phase boundary, [x = 0.3–0.45]. The high values of pyroelectric coefficient achievable, in particular for low x compositions [x = 0–0.1], suggest potential application of these materials as highly efficient and versatile field-stabilized devices.

Identification of the morphotropic phase boundary in the lead scandium tantalate-lead titanate solid solution system

A morphotropic phase boundary between rhombohedral and tetragonal phase regions has been identified to lie in the composition range x=0.4–0.45 by means of X-ray diffraction, and dielectric, pyroelectric, and piezoelectric measurements. Some curvature to this boundary at high temperatures is indicated in the temperature dependences of the dielectric constants and pyroelectric coefficients of poled specimens.

Optical properties of hot pressed relaxor ferroelectrics

Abstract The optical properties of hot pressed transparent ceramics based on the relaxor ferroelectric (1-x)Pb (Mg1/3,Nb2/3)O3−xPbTiO3 (known as PMN-PT) solid solution system have been examined in the visible region. We report transmission as a function of wavelength, refractive indices as a function of temperature and wavelength, and quadratic electro-optic coefficient data for the 632.8 nm HeNe laser wavelength. For our particular ceramic compositions, .93(Pb0.99La0.01)(Mg1/3,Nb2/3)O3−.07PbTiO3 and .90 PMN−.10 PT, the refractive index dispersion is well described by a single term Sellmeier equation. The observed temperature dependence of the refractive indices n(T) can be discussed in terms of polar microregions which alter the refractive indices in these ceramics via the quadratic electro-optic effect. Transverse quadratic electro-optic coefficients measured were in accord with those reported for other Pb containing perovskite oxides.

Electrical and optical properties of relaxor ferroelectrics

Abstract The dielectric and optic/electro-optic properties of hot-pressed ceramics of composition (1−x)(Pb1−y −La y )(Mg⅓Nb2/3)O3 − xPbTiO3 (y = 0.01) have been investigated. The materials exhibit high peak dielectric constants (>20000) with typical relaxor ferroelectric behavior. The ceramics are adequately transparent for optical and electro-optical evaluation with transmission better than 50% at 600 nm. High refractive indices are observed (>2.5 at 632.8 nm) and the dispersion of the refractive index is well described by a single-term Sellmeier equation. The temperature dependence of the refractive index exhibits a linear region above 390°C and a polarization induced decrease of the index via the electro-optic effect below this temperature. The transverse quadratic electro-optic coefficients, (R11–R12) and (g11–g12), were evaluated both as a function of temperature and frequency. Electro-optic switching experiments indicate rapid response of less than 1 μsec, suitable for transverse shutter mode operation.

Variable structural ordering in lead scandium tantalate-lead titanate materials

Abstract A phase region of variable order-disorder [VOD] has been identified in this study for compositions in the range [x- 0.0–0.075] (x: mole fraction PbTiO3). Materials from this region retain some degree of long-range ordering of 5-site cations as evidenced by x-ray and electron diffraction which is enhanced with post-sintering annealing. Annealed ceramics exhibit sharp dielectric responses [K(T] and near-normal first-order ferroelectric behavior while as-fired specimens with lesser degrees of long-range ordering show the more diffuse and dispersive characteristics of a relaxor ferroelectric.

(Pb, Bi)(Ti, Fe, Mn)O3/Polymer 0-3 composites for hydrophone applications

The hydrostatic piezoelectric response of composite materials incorporating (Pb1-xBix)(Ti1-xFex)O3 ceramic fillers from the highly anisotropic tetragonal region of the solid solution system in the vicinity of the morphotropic phase boundary were measured and compared. The considerable difficulty in poling and, hence, the diminished piezoelectric response encountered as the composition of the filler is shifted closer to the phase boundary was determined to be largely due to the high conductivity of the BiFeO3-rich compositions. The ceramic was modified with Mn in an attempt to lower its conductivity. Composites incorporating the Mn-doped filler poled more rapidly and easily than the undoped material and ultimately achieved a hydrostatic figure of merit, dhgh, 40% better than that observed for the undoped samples. Among the samples investigated, the highest hydrostatic figures of merit were exhibited by samples containing the doped and undoped x = 0.5 fillers. The hydrostatic response remains stable over a ...

Soft piezoelectric (1−x)Pb(Sc1/22Ta1/2)O3-(x)PbTiO3 ceramics with high coupling factors and low QM

Abstract The piezoelectric behavior of materials from the (1-x)Pb(Sc1/22Ta1/2)O3-(x)PbTiO3 solid solution system has been investigated. The [x = 0.45] composition in particular has exhibited an outstanding piezoelectric response [d33 = 650 (pC/N). kt = 0.5, kp = 0.61. k33 = 0.73] and a low mechanical quality factor [QM = 30]. These features make it a promising candidate for a variety of piezoelectric sensor applications. The difficulties involved in effectively poling a bar sample and a means to avoid these problems are also addressed.

Characterization of (1-x)Pb(Mg1/3Nb2/3)O3 — (x)PbTiO3 and Pb(Sc1/2Ta1/2)O3 transparent ceramics prepared by uniaxial hot-pressing

Abstract Transparent relaxor ferroelectric ceramics of (1-x)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 and Pb(Sc1/2Ta1/2)O3 have been prepared by low temperature uniaxial hot-pressing. The ceramics are highly dense (> 99.5% theor.) and transmit throughout the visible. The addition of excess PbO and La2O3 and post-pressing heat treatment are found to enhance transparency. The ceramics have been characterized for phase purity, development of microstructure, dielectric behavior and optical transmission in order to determine optimum conditions.

Piezoelectric properties of modified lead scandium tantalate ceramics

Abstract The piezoelectric properties of selected compositions from the solid solution system (1 − x)Pb(Sc 1 2 Ta 1 2 )O 3 t-(x)PbTiO 3 have been investigated primarily by the resonance method. The peak values of the piezoelectric strain coefficient (d33 = 655 pC/N) and the electromechanical coupling factors (kt = 0.5, kp = 0.61 and k33 = 0.73) accompanied by an exceptionally low value of the mechanical quality factor (Qm = 30) were observed for the x = 0.45 composition. The strong piezoelectric response of this composition in conjunction with its low mechanical quality factor make it an attractive candidate for a variety of transducer applications.