Richard L. Gentilman

Design, fabrication, and properties of sonopanelTM 1–3 piezocomposite transducers

Abstract 1–3 piezocomposite materials, manufactured by PZT ceramic injection molding and marketed by Materials Systems under the trade name “SonoPanelTM”, have been adapted for operation under a wide variety of undersea conditions. These transducer materials have been modified to enhance specific performance characteristics by varying the PZT ceramic element type and layout, the polymer matrix properties, and by configuring the device to couple efficiently into water in both transmit and receive operation. Piezocomposite SonoPanelsTM have high and very broadband receiving voltage sensitivity (RVS). In one typical configuration (6mm thick 1–3 composite with 15 volume % PZT-5H, soft polymer matrix and stiff coverplates), the nonresonant RVS is −187 ± 2dB re IV/μPa from 0.1 to > 100kHz. The nonresonant transmit voltage response (TVR) of a 100mm square SonoPanelTM is 147dB at 50kHz, and increases linearly at 40dB per decade to 175dB at resonance. SonoPanelsTM have been driven at rms electric field levels up t...

Ultrafine scale piezoelectric composite materials for high frequency ultrasonic imaging arrays

Intravascular and endoscopic acoustic imaging typically require high ultrasonic operating frequencies, over 7 MHz. At these frequencies the ceramic transducer dimensions become very small; pitches in the order of 20 to 80 /spl mu/m are needed. Moreover, such arrays must be compatible with existing interconnect approaches and be fabricated at low cost. These piezoelectric transducer array requirements severely challenge the ability of conventional PZT ceramic technologies in terms of cost-effective fabrication. To meet the demand for such transducer shapes, MSI has developed a net shape ceramic injection molding process for production of piezoelectric ceramics in complex shapes. Using this technique, MSI has produced ultrafine scale 2-2 piezocomposite arrays having PZT elements less than 25 /spl mu/m wide and pitches under 50 /spl mu/m. This paper reviews recent advances in the net shape molding technology, and compares the characteristics of an injection molded 7 MHz 2-2 configuration with that of a similar array prepared by conventional dicing.

Manufacturing of 1-3 piezocomposite SonoPanel transducers

A manufacturing capability has been established for 1-3 PZT-polymer composite materials and transducers. Uniform arrays of identical PZT rods are formed by a cost-effective ceramic injection molding process. Sintered and poled 1-3 ceramic preforms, containing 361 PZT rods 1.1 mm diameter on a 50 mm square base plate, are arranged to produce 15 or 30 PZT volume percent composite materials with a hard or soft polymeric matrix. More than 2000 identical PZT preforms were produced and more than thirty 250 mm square SonoPanel transducers have been manufactured. The transducers have been found to be well suited for a variety of underwater acoustic applications. Fifteen SonoPanels have been incorporated into a 3 X 5 array as part of a Navy system demonstration.

Processing and application of solid state converted high-strain materials

The property enhancement offered by single crystal relaxor ferroelectrics combined with the manufacturability advantages offered by injection molding has the potential of producing single crystal 1-3 piezocomposites at an affordable production-viable rate. Two methods of texturization/recrystallization are being evaluated: an integrated multi-seed process and epitaxial growth. The integrated seed approach involves incorporation of oriented single crystal PMN-PT seeds into injection molding feedstock prior to fabrication of 1-3 ceramic preforms. After sintering, an additional texturization and growth step is carried out. This step is intended to drive recrystallization at multiple sites within the ceramic body extending the oriented texture throughout the matrix. The epitaxial growth approach involves nucleation and growth in the dense ceramic body initiated from a compatible external seed crystal. Recrystallization is achieved through direct contact between a ceramic preform and a seed substrate coupled with appropriate thermal and atmospheric growth conditions.

A sonar application of 1‐3 piezocomposite material

Injection molded piezocomposite materials have significant potential for improving the performance of Navy and civilian acoustic systems. Specifically, a 1‐3 configuration based on PZT exhibits attractive properties for hydrophone array systems where the elements are many and/or small. An array of 1‐3 composite hydrophones has been manufactured and tested as a potential replacement for a currently used 0‐3 composite (Piezo‐rubber) hydrophone array developed for a high frequency sonar. For this application, several experimental composite panels have been manufactured from injection molded PZT‐5H and PZT‐4 ceramic, each of which contains 20 or 40 elements. Acoustic modeling and test results have been obtained for two configurations of interest: the array panel alone; and the panel installed in a housing similar to the finished hydrophone module. Results will be presented which include: predictions of sensitivity and phase response; predictions of self‐noise candidate material, including future designs with ...

Development of 1–3 and 2–2 piezocomposite transducers

1–3 and 2–2 piezoelectric ceramic/polymer composites offer design versatility and performance advantages over monolithic piezoelectric ceramic and monolithic piezoelectric polymer devices in both resonant and nonresonant transducer applications. Recently, a new process, viz., ceramic injection molding, has been applied to solve the difficulties of cost‐effectively manufacturing the arrays of fine PZT ceramic elements required for composite transducer assembly. As a result, these materials are now available in commercial quantities for the first time. In this paper, Materials Systems, Inc. briefly introduces its PZT ceramic injection molding transducer manufacturing process, and then reviews the performance of various 1–3 composite transducer designs as a function of composite layout, materials, and transducer performance enhancement features, such as stiff cover plates and Poisson’s ratio decoupling. The performance of several transducer designs in both nonresonant sensing and actuating undersea applicati...

Application of piezoelectric composites and net‐shape PZT ceramics as acoustic sensors and actuators

A ceramic injection molding process is used to custom manufacture piezoelectric composites for both sensors and actuators with operational frequencies from 100 Hz and 10 MHz. These piezoelectric composites can be specifically tailored to couple acoustic energy into and from a wide variety of mediums including air, water, biological tissue, polymers, composites, and metals. Both 1‐3 and 2‐2 piezoelectric composites have been made with different lead zirconate‐titanate (PZT) formulations, element dimensions, PZT volume fractions, and polymeric matrices. Piezoelectric composite transducers are easily conformed to various substructures, shaded to adjust beam patterns, and sectioned into arrays for imaging. Examples include face‐plated SonoPanels (and stiff matrix 1‐3 piezoelectric composites for underwater actuation, sensing, and imaging. SmartPanels, capable of both sensing and actuating, have been recently introduced for active surface control. These devices integrate 1‐3 piezoelectric composite actuators a...

Piezoelectric composite transducers

Piezoelectric ceramic/polymer composites have found increasing use in high resolution medical ultrasound systems and advanced Navy underwater acoustic applications. Composite transducers offer design versatility and performance advantages over monolithic piezoelectric ceramic and monolithic piezoelectric polymer devices under both sensing and actuating conditions. In particular, composite transducers allow improved acoustic impedance matching to water and body fluids, improved lateral mode cancellation, enhanced thickness mode coupling coefficient, and naturally broad bandwidth. However, applications for these versatile transducers have been limited by the difficulties of cost‐effectively manufacturing the arrays of fine PZT ceramic elements required for composite assembly. At Materials Systems, Inc., ceramic injection molding has been developed into a viable net‐shape process for making complex‐shaped, fine scale PZT 1‐3 and 2‐2 transducer element arrays. This presentation describes the injection molding...