Kurt M. Rittenmyer

Piezoelectric 3–3 composites

Abstract Piezoelectric composites of PZT and polymers were prepared by mixing tiny plastic spheres with PZT powder in an organic binder and firing the mixture to give a ceramic skeleton. After cooling, the skeleton was back-filled with polymer and poled. Dielectric and piezoelectric properties were measured on samples ranging from 30 to 70 volume % PZT, and compared with a rectangular skeleton model for 3–3 composites. Composites containing 50% PZT-50% silicone rubber appear especially useful for hydrophone applications with dhgh products a hundred times larger than PZT.

Electrostrictive ceramics for underwater transducer applications

The electromechanical properties of two electrostrictive materials designed for use in underwater acoustic applications are determined as functions of temperature and electric field. The materials are 0.859 Pb(Mg1/3Nb2/3)O3–0.141 PbTiO3 doped with 2.5% SrTiO3 or BaTiO3. Dielectric properties are determined as functions of temperature and electric field. The equivalent piezoelectric coefficients were found as functions of temperature to be equal to or superior to the lead zirconate–titanate ceramics at very modest dc bias fields (2 kV/cm) at temperatures in the range from 10 to 35 °C. Outside of this temperature range, the piezoelectric and dielectric coefficents decrease rapidly. Electromechanical losses were found to be sufficiently small for the SrTiO3 composition but not the BaTiO3 composition.

Ferroelectric composites for hydrophones

Abstract Considerations of the influence of crystal symmetry, macrosymmetry, and interphase connectivity have been used to explore possible macrostructures of interest as piezoelectric composites. Based on these design considerations, polymer-ceramic composites have been fabricated with 3–3 phase connectivity by the replication of natural template structures such as coral, or by a simplified fabrication technique of mixing volatilizable plastic spheres and PZT powders. 1–3 or 2–3 composites were made by perforated method. Polymer-Ceramic composites with 3–1 phase connectivity were made by embedding PZT rods or PZT spheres in various polymers. A modified connectivity model with 3–1–0 phase connectivity was introduced to improve the Poisson contraction problem found in 3–1 composites. In 3–1–0 composites voids were introduced into the polymer matrix to form a third phase which is isolated. All types of composites have been studied and it is shown that they have slightly lower permittivity, greatly improved ...

Temperature dependence of the electromechanical properties of 0–3 PbTiO3‐polymer piezoelectric composite materials

The electromechanical properties of 0–3 ceramic–polymer composite piezoelectric materials manufactured by NTK Corporation in Japan have been measured as a function of temperature using several techniques. The elastic, dielectric, and piezoelectric constants were measured by fitting the complex admittance vs frequency spectrum to a model of a piezoelectric resonator near the electromechanical resonance [Xu et al., J. Wave Mater. Interact. 2, 105–181 (1987)]. These properties are shown to vary significantly with temperature as a result of the glass‐transition region of the polymer phase. The theory of viscoelasticity in polymers discussed by Ferry (WLF theory), which explains the influence of the glass transition on the elastic properties of polymers, is used to describe the temperature dependence of the elastic and dielectric properties of the composite materials. The temperature dependence of the dielectric permittivity is shown to be similar in form to the temperature dependence of the elastic properties...

Electrostriction in fluoride perovskites

Abstract The values of the hydrostatic electrostriction constant Qh = Q11 + 2Q12 have been obtained for the perovskite structure fluorides KCaF3, KMnF3, KMgF3, and KZnF3 by measuring the pressure dependence of the dielectric stiffness. The values range from 0.28 to 0.85 m4/C2 and are as expected from theory more than an order of magnitude larger than the Qh for the oxide perovskites. Non-linearity in the response appears too large to be explained by the elastic non-linearity and a sixth-order electrostriction is invoked to explain the observed behavior.

Temperature dependence of the dielectric constant of KMnF3

Abstract Precise and careful measurements of capacitance vs temperature on KMnF3 single crystals are made. The results indicate the stronger interaction of the soft mode with the acoustic modes in KMnF3 compared to that in SrTiO3 which is evident from the anomaly in the dielectric constant at the transition temperature.

Electrostriction and its relationship to other properties in perovskite-type crystals

Abstract Measurements of the fourth and sixth-order electrostriction constants have been performed on several fluoride perovskite single crystals. The results are compared with those observed in other similar materials, and the relationships between electrostriction and some physical properties are examined.

Electroacoustic evaluations of 1–3 piezocomposite rings

Two 1–3 piezocomposite rings have been recently electroacoustically evaluated for sonar application. The two rings have outer diameters of 345 mm, 101.6‐mm height and a wall thickness of 5 mm. Both have a 5% Navy type II piezoceramic volume concentration loading. The host epoxy of one ring is soft while the other is hard. Both rings had 17.78 by 25.4 mm rectangular elements etched into a 3 by 3 element pattern in their outer electrode for direct in‐water performance comparison with a previous design utilizing individual elements of the same dimensions [Howarth et al., J. Acoust. Soc. Am. 91, 2325–2326 (A) (1992)]. The in‐water measurements include wide‐band free‐field voltage sensitivity (FFVS), transmitting voltage response (TVR), and radiation patterns in both the XY and XZ planes. A laser Doppler vibrometry was used for in‐air evaluation of the piezoelectric charge constant and surface displacement. Interelement coupling data will also be presented. [Work sponsored by the Office of Naval Research.]

Electromechanical properties of new electrostrictive materials for underwater acoustical applications

Electrostrictive ceramics are known to be capable of generating strains that far exceed those of conventional piezoelectric lead–zirconate–titanate (PZT) ceramics. Several lead–magnesium–niobate (PMN) compositions developed earlier were useful only at higher temperatures than those of interest to the sonar community. A new barium‐modified PMN–PT ceramic is described. This material can operate at lower temperatures and has very low losses, making it a prime candidate for high‐power sonar transducer applications. Another family of electrostrictive materials capable of generating large strains is lanthanum‐modified PZT (or PLZT). These materials exhibit strains up to 0.1% along with extremely high dielectric strength, but their hysteresis losses are higher than those of PMN or PMN–PT ceramics. Since the maximum possible strain output is usually the important parameter in actuator applications, the PLZT family may have potential for new actuator designs. Strain measurements for these new electrostrictive cera...