Ferroperm™ PiezoceramicsInSensor™

Piezoceramics

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Contents

3 Meggitt Sensing Systems4 Piezoelectric materials from Meggitt Sensing Systems6 Terminology8 Piezoelectric materials10 Material properties12 Ferroperm™ Piezoceramics14 InSensor™15 Applications

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Piezoelectric materials

By definition, a piezoelectric material generates a charge when put under pressure and will show a change in volume when an electrical field is applied. It can be used as a transducer material for transforming electrical energy into mechanical energy and vice versa. Furthermore, applying an A/C voltage to the material will cause it to vibrate and thus generate mechanical waves with the same frequency as the electrical voltage. Similarly, if a mechanical vibration is applied, a charge of proportional amplitude and frequency will be generated.

History

Piezoelectric activity was first discovered in single crystals by J and P Curie in 1880. However, it was not until 1946 that scientists discovered that BaTiO3 ceramics could be made piezoelectric by applying an electric field. This led to the discovery of a number of piezoceramic compositions, including the lead zirconate titanate (PZT) family in 1956. With the PZT family’s increased sensitivity and higher operating temperature, it soon replaced BaTiO3 in many existing devices and is still the most widely used piezoceramic composition. The ceramic materials have several advantages over traditional single crystals, including higher sensitivity (up to several hundred times higher) and ease of fabrication into a variety of shapes and sizes. In contrast, single crystals must be cut along certain crystallographic directions, limiting the possible geometrical shapes.

Meggitt Sensing Systems

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Piezoelectric materials from Meggitt Sensing Systems

History Meggitt Sensing Systems’ piezoelectricmaterials originated with Ferroperm™ Piezoceramics registered in Den-mark in May 1952 as a private en-terprise producing iron dust cores, ferrites and ceramic capacitors. In 1955, piezoelectric ceramics based on barium titanate were added to the product range. The business was transferred to a limited company, “The Industrial company Ferroperm A/S”, in 1957. This company steadily expanded its activities and at one time also produced multilayer ce-ramic capacitors and optical interfer-ence filters. In 1989, its piezoelectric division moved to accommodate further expansion, becoming a sepa-rate limited company in 1998. After a short period under American owner-ship in 2001, a management buy-out was completed in 2002. In 2008, the company was acquired by Meggitt PLC where it operates as a fully inte-grated part of the Meggitt group’s sensing systems division from mod-ernised and expanded facilities in Denmark.

Today’s piezoelectric components from Meggitt Sensing Systems are marketed under the Ferroperm ™ Piezoceramics and InSensor™ brands. New products are developed con-tinuously and the portfolio includes a full industrial program of traditional PZT suitable for a variety of applica-tions, relaxor-based solid solutions optimized for imaging applications, bismuth titanates for use at elevated temperatures, modified lead titanates and special high-power compositions for ultrasonic therapy, low-acoustic impedance materials for easy acoustic coupling and an electrostrictive mate-rial, lead magnesium niobate, PMN. More recently InSensor™ thick-films integrated with functional substrates have celebrated commercial break-throughs with the promise of very high growth in future medical systems and integrated energy harvesting and sen-sor devices.

Meggitt Sensing Systems in Denmark is certified to ISO 9001:2008 and ISO 14001:2004.

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Research and development

Meggitt Sensing Systems has a long standing commitment to R&D and the Danish site currently spends ap-proximately 15% of its turnover on R&D projects. There is close collaboration with leading universities throughout Europe. Over the last 20 years, Meggitt Sensing Systems in Denmark has been involved continuously in large European projects including Brite/Euram, Eureka, Cost, Esprit, FP5 and FP6. Research topics include high sensitivity materials, lead-free materials, thick-film technol-ogy and ultra-high temperature piezo-electric ceramics.

Policy

More than 95% of the products from the Ferroperm™ Piezoceramcs and InSensor ™ lines are tailored for customers’ individual requirements. The main focus throughout our entire production process is to provide mate-rials and components with the highest possible reproducibility of properties and parameters and to obtain the lowest ageing rates in the industry. This enables customers to optimize design and improve performance and production flow, thereby contributing to improved competitiveness in their markets.

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Piezoceramics

After firing, piezoelectric ceramics comprise small grains (crystallites), each containing domains in which the electric dipoles are aligned. These grains and domains are randomly oriented, so the net electric dipole is zero, i.e. the ceramics do not exhibit piezoelectric properties. The applica-tion of a sufficiently strong DC-field will orient the domains in the field direction, as close as the orientation of the crystal axes allows. This ability to change the domain orientation and achieve a net polarization is called ferroelectricity. A remanent polariza-tion can be created in piezoelectric materials. After the poling process is complete, a voltage with the same polarity as the poling voltage causes expansion along the poling axis and contraction perpendicular to the poling axis. Compressive or tensile forces applied to the ceramic element will generate a voltage.

Definitions

In piezoelectric ceramics, because material characteristics depend on the direction of the applied field, displacement, stress and strain, superscripts and subscripts indicating direction are added to the symbols. The direction of polarization is gen-erally designated as the z-axis of an orthogonal crystallographic system.

The axes x, y and z are respectively represented as 1, 2 and 3 directions and the axes shearing around these axes are represented as 4, 5 and 6. This is shown schematically on page 7. The various piezoelectric material constants are generally expressed with subscripts using this notation. Planar modes are sometimes ex-pressed with a subscript ´p´ and the thickness mode with a subscript ´t´. The first subscript gives the direction of the electrical field associated with the voltage applied or the charge pro-duced. The second gives the direction of mechanical stressor strain. Super-scripts indicate a constant mechanical or electrical boundary condition.

Parameter Synbol Condition

Stress T Mechanically free

Field E Electrical short circuit

Displacement D Electrical open circuit

Strain S Mechanically clamped

Curie temperature

The crystal structure of a material changes at the Curie temperature, Tc, from piezoelectric (non-symmetrical) to a non-piezoelectric (symmetrical) form. This phase change is accom-panied by a peak in the dielectric constant and a complete loss of all piezoelectric properties.

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Piezoelectric materials

Lead zirconate titanate (soft)

Type Pz23, Pz27 Pz29 and P188 These materials are characterized by relatively high Curie tempera-tures, low mechanical QM factor and high electrical resistivity at elevated temperatures. Pz23,Pz27 and P188 have moderate dielectric constants, high charge and electro-mechanical coupling coefficients and operating temperatures up to above 250°C. Type Pz29 has a lower Curie temperature, but higher dielectric constants, and higher coupling coefficients. Ceramics from these compositions are par-ticularly useful in a wide spectrum of applications ranging from combined resonant transducers for medical and flow transducers to accelerometers, pressure sensors and NDT.

Lead zirconate titanate (hard)

Type Pz24, Pz26, Pz28, P762 and P189 These materials are characterized by high coercive field, high mechani-cal QM factor and low dielectric loss. Pz24 has a very low dielectric con-stant. Pz26, Pz28, P762 and P189 are high power and low loss materials. Typical applications include under-

water acoustics, high voltage genera-tors, high-power ultrasonics, such as cleaning, welding and drilling devices.

Very soft relaxor-based compositions

Type Pz21, P194 and Pz59These materials are characterized by a very high dielectric constant, high charge coefficient and high electro-mechanical coupling coefficients. They are used mainly in medical and sonar imaging systems, such as phased arrays and composites.

HIFU compositions

Type Pz34, Pz52 and Pz54Pz34 has large hyphenated anisot-ropy, low dielectric constant and have extremely low grain size. It is very stable over time, temperature and frequency. We recommend it for single element high frequency medical transducers and applica-tions where interference from radial modes is a significant problem. Pz52 and Pz54 have very high permittivity, high mechanical Qm values, and low dielectric losses, making them the op-

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timum choice for applications where the highest power levels are required in combination with the smallest possible volume. The materials were developed to meet the challenges dictated by the rapid development in ultrasonically-assisted surgery and therapeutics.

Low-acoustic impedance family

Type Pz31, Pz36, Pz37 and Pz39This new family is characterised by a porous structure. Tolerances might therefore vary more than standard

and be more dependent on size and geometry. It is used mainly in NDT systems where the acoustic matching is critical.

Bismuth titanate

Type Pz46 This material has a very high Curie temperature (> 600°C) and working temperatures of up to 550°C. It is used in high temperature applications, such as accelerometers, flow meters and pressure sensors.

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Traditional Soft PZT Traditional Hard PZT

Pz23 Pz27 P188** Pz29 Pz24 Pz26 Pz28 P762** P189**

Navy Type / Industry "equivalent" Symbol Unit N/A Navy 2 PZT5A

Navy 2 PZT5A

Navy 6 PZT5H "ZT7A Navy 1

PZT4DNavy 3 PZT8

Navy 1 PZT4D

Navy 3 PZT8

Eletrical Properties

Relative Free Dielectric Constant (1 kHz) K33T 1500 1800 1850 2900 400 1300 1030 1300 1150

Dielectric dissipation factor (1 kHz) tan d (3s) 10-3 15 17 20 19 3 3 4 5 3

Curie Temperature TC > ºC 350 350 340 235 330 330 330 300 320

Recommeded maximum working range T < ºC 250 250 240 150 230 230 250 200 220

Electromechanical Properties

Coupling factors kp 0,52 0,59 0,65 0,64 0,50 0,56 0,58 0,58 0,51

kt 0,45 0,47 0,49 0,52 0,52 0,47 0,47 0,47 0,46

k31 -0,29 -0,33 -0,37 -0,37 -0,29 -0,33 -0,34 -0,35 -0,32

k33 0,65 0,70 0,74 0,75 0,57 0,68 0,69 0,68 0,65

Piezoelectric charge coefficients -d31 10-12 C/N 130 170 185 240 55 130 120 130 108

d33 10-12 C/N 330 425 425 575 90 300 275 300 240

d15 10-12 C/N 420 500 400 700 150 330 400 280

Piezoelectric voltage coefficients g31

-10-3 V m/N 10 11 11 10 16 11 13 -11 -11

g33

10-3 V m/N 25 27 26 23 54 28 31 26 23

Frequency constants Np m/s 2160 2010 1970 1970 2400 2230 2180 2250 2350

Nt m/s 2030 1950 2020 1960 2100 2040 2010 2050 2150

N31 m/s 1480 1400 1450 1410 1670 1500 1600 1650 1750

N33 m/s 1600 1500 1890 1500 1600 1800 1500 1920 2060

Mechanical Properties

Density P kg/m3 7700 7700 7700 7460 7700 7700 7700 7600 7650

Mechanical quality factor Qm,tE 100 80 80 90 >1000 >1000 >1000 >600 >1000

Material properties

* Pz31, Pz36, Pz37, Pz39 are a new family of mateials containing a porous structure. Tolerances might therefore vary more than standard, and be more dependent on size and geometry. ** P188,P189, P762 and P194 are a part of a full technology transfer of the Quartz & Selice programme from Saint-Gobain Quatz to Meggitt A/S in 2010 All Please be aware that extreme dimensions and geometries can lead to exaggeration in tolerances in all materials.

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Low-Acoustic Impedance Family HIFU Family Very Soft Relaxor-Based Comp High Temp

Pz31* Pz36* Pz37* Pz39* Pz34 Pz52 Pz54 Pz21 P194** Pz59 Pz46

Navy Type / Industry "equivalent" Symbol Unit K81 N/A N/A N/A PZT2 N/A N/A 3203HD 3203HD N/A K15

Eletrical Properties

Relative Free Dielectric Constant (1 kHz) K33T 295 610 1150 1750 210 1900 2700 3800 4500 5100 120

Dielectric dissipation factor (1 kHz) tan d (3

s) 10-3 4 3 17 19 14 3 3 18 25 18 4

Curie Temperature TC > ºC 330 330 350 220 400 235 220 220 185 150 650

Recommeded maximum working range T < ºC 230 230 250 130 150 150 130 130 85 80 550

Electromechanical Properties

Coupling factors kp 0,30 0,26 0,35 0,18 0,07 0,60 0,57 0,59 0,61 0,55 0,03

kt 0,52 0,52 0,52 0,53 0,40 0,53 0,48 0,47 0,50 0,46 0,20

k31 -0,15 -0,05 -0,35 -0,35 -0,34 -0,38 -0,02

k33 0,60 0,40 0,70 0,70 0,70 0,70 0,09

Piezoelectric charge coefficients -d31 10-12 C/N 5 170 200 250 305 2

d33 10-12 C/N 160 230 350 480 50 440 440 600 640 645 18

d15 10-12 C/N 40 620 16

Piezoelectric voltage coefficients g31

-10-3 V m/N 3 7 -7 2

g33

10-3 V m/N 54 40 40 28 25 25 20 18 15 17

Frequency constants Np m/s 1550 2770 2090 2100 2030 1930 1955 2470

Nt m/s 1520 1270 1400 1190 2200 1960 2000 1970 2000 2050 2000

N31 m/s 2050 1375 1380 1900

N33 m/s 1325 1830

Mechanical Properties

Density P kg/m3 6200 5600 6000 5800 7550 7350 7800 7780 7900 7900 6550

Mechanical quality factor Qm,tE 900 500 50 70 >1000 550 >1000 65 60 40 >600

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Ferroperm™ Piezoceramics

Reproducibility

Ferroperm™ Piezoceramics has been synonymous with the highest quality piezoelectric ceramics for more than 50 years. This is based on purity of raw materials and process control, from the production of material pow-ders to the finished poled and elec-troded part. We insist that a com-plete pilot production is completed and approved before each new mate-rial batch is released for production, ensuring that mechanical, dielectric and piezoelectric parameters fulfil our strict quality standards.

The data for these individual pilot productions are stored in a database to which production management al-ways has access. The figures on this page show the variation in the free dielectric constant of the two most common materials (Pz26 and Pz27)

over more than 15 years’ production. This illustrates the unique batch stability of Ferroperm™ materials. The measurements, performed on calibrated equipment in line with US Navy, IEEE and CENELEC standards, comprise more than 300 different batches of each material and are made on standardised discs from pilot productions before each batch is released. All parameters have varia-tions well within an interval of only ± 5%— the lowest on the market. This high reproducibility ensures that parts ordered continuously or at intervals perform almost identically, regardless of powder batch. This results in low-cost, very low-level re-quirements for impedance matching, frequency tuning and dimensioning of housing and a decrease in rejected finished parts.

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InSensor™

InSensor™ is a fully integrated unit within Meggitt Sensing Systems’ Danish facility and specialises in manufacturing integrated piezoelectric thick film devices. InSensor™ active materials are based on high-quality Ferroperm™ piezoelectric powders, but modified so it can be deposited on a variety of substrates.

Substrates

• silicon (compatible with MEMS)• LTCC• alumina• special ceramics (acoustically engineered)• stainless steel

Applications

• ultra-high bandwidth focused acoustic transducers• MEMS accelerometers • energy harvesting• phased and annular arrays• pMUTs

The team of researchers and produc-tion engineers behind the InSensor™ product line are ready to develop and produce new devices for individual ap-plications.

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Piezoelectric ceramics are used in a very broad range of applications due to their excellent properties, such as high sensitivity, ease of manufacture and the poten-tial to pole the ceramic in any direction.

• Accelerometers for test and measurement and continuous condition monitoring• Medical transducers for imaging, HIFU, IVUS, and cleaning of blood veins• Underwater acoustics for echo sounders, sonar systems, fish-finders and seabed mapping• Flow meters for blood, industrial processes and waste water management• Non-destructive testing in the aerospace, offshore and industrial sectors

Applications

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About Meggitt Sensing SystemsMeggitt Sensing Systems, a leading supplier of sensing and monitoring systems measuring physical parameters in extreme environments, has operated through its antecedents since 1927 under the names of Ferroperm Piezoceramics, Lodge Ignition, Endevco, Sensorex, ECET, Vibro-Meter and Wilcoxon Research. Today, their capabilities and facilities have been integrated under one Meggitt division, providing complete systems from a single supply base. Its unique yet wide portfolio includes high technology products and systems for civil and military aerospace and the energy, power generation, nuclear, oil and gas, industrial, laboratory measurement, automotive and space markets.

Meggitt Sensing Systems’ development and manufacturing sites are located in Switzerland, France, UK, Denmark and the USA. An extensive sales and support network extends across Europe, Asia and the Americas.

About Meggitt PLCMeggitt PLC, headquartered in the United Kingdom, is an international engineering group employing some 9,500 people worldwide across North America, Europe and Asia. It specialises in high performance components and sub-systems for aerospace and defence markets primarily but applies its core sensing and controls technologies to land and marine-based gas turbines and the medical, mainstream industrial, test engineering and transporta-tion sectors.

Meggitt Sensing Systems Meggitt A/S Hejreskovvej 18A DK-3490 Kvistgaard Denmark

Tel: +45 49 12 71 00Fax: +45 49 13 81 88

pz@ferroperm.netthom.wurlitzer@meggitt.com

www.meggitt.comwww.meggittsensingsystems.com

www.ferroperm.net

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