Handbook of Advanced Dielectric, Piezoelectric and Ferroelectric Materials

Synthesis, Properties and Applications

Z-G Ye

• Publisher: Woodhead Publishing
• Year: 2008
• Print ISBN: 9781845691868
• eBook ISBN: 9781845694005
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

This comprehensive book covers recent developments in advanced dielectric, piezoelectric and ferroelectric materials. Dielectric materials such as ceramics are used to manufacture microelectronic devices. Piezoelectric components have been used for many years in radioelectrics, time-keeping and, more recently, in microprocessor-based devices. Ferroelectric materials are widely used in various devices such as piezoelectric/electrostrictive transducers and actuators, pyroelectric infrared detectors, optical integrated circuits, optical data storage and display devices.The book is divided into eight parts under the general headings: High strain high performance piezo- and ferroelectric single crystals; Electric field-induced effects and domain engineering; Morphotropic phase boundary related phenomena; High power piezoelectric and microwave dielectric materials; Nanoscale piezo- and ferroelectrics; Piezo- and ferroelectric films; Novel processing and new materials; Novel properties of ferroelectrics and related materials. Each chapter looks at key recent research on these materials, their properties and potential applications.Advanced dielectric, piezoelectric and ferroelectric materials is an important reference tool for all those working in the area of electrical and electronic materials in general and dielectrics, piezoelectrics and ferroelectrics in particular. - Covers the latest developments in advanced dielectric, piezoelectric and ferroelectric materials - Includes topics such as high strain high performance piezo and ferroelectric single crystals - Discusses novel processing and new materials, and novel properties of ferroelectrics and related materials

Part I

High-strain, high-performance piezo- and ferroelectric single crystals

1

Bridgman growth and properties of PMN–PT-based single crystals

P. Han; J. Tian; W. Yan H. C. Materials Corporation, USA

1.1 Introduction

1.1.1 Background

Continual development in acoustic transduction devices has been made since the end of World War II. This progress came about largely due to the availability of improved materials. The example of PZT (lead zirconate titanate) piezoelectric ceramics is well known. Recently, progress in the growth and characterization of PMN–PT (lead magnesium niobate–lead titanate)-based piezoelectric crystals has promoted the development of the next generation of acoustic transduction devices.

The recent shift in focus from blue water to littoral operations for the US Navy has placed additional requirements on sonar systems. New materials of high energy density and improved properties are needed for enhanced sonar transduction performance. Material property improvements include:

• increased strain to enhance acoustic source level;

• increased electromechanical coupling to broaden bandwidth;

• increased energy density to reduce transducer weight and give higher efficiencies;

• reduced hysteresis to produce greater thermal stability;

• increased sensibility to improve signal/noise ratio.

A breakthrough was announced at the Piezoelectric Crystal Planning Workshop¹ sponsored by the Office of Naval Research in May 1997. Single crystals of PZN–PT (lead zinc niobate–lead titanate) and PMN–PT near MPB (morphotropic phase boundary) compositions exhibit extraordinary piezoelectric properties, namely, electrical field-induced strains exceeding 1%, and electromechanical coupling exceeding 90% (compared with 0.1% and 70–75%, respectively, in the state-of-the-art PZT piezoceramics)^2,3. These perovskite relaxor ferroelectric crystals have opened up new opportunities not only in current acoustic transduction devices, where traditional PZT ceramics are used, but also in exploration of new applications, such as medical ultrasonics, non-destructive detection, marine seismic exploration and energy harvesting. These new crystals of giant-piezoelectric properties will enable “revolutionary” developments for the next generation of acoustic transduction devices. Thus, there is an urgent need to develop crystal-growth techniques for the fabrication of large, high-quality piezoelectric crystals at industrial scale.

1.1.2 Challenges in the growth of large PMN–PT crystals

It is a great challenge to develop a cost-effective method for the growth of the high-strain piezocrystals of large sizes (75–100 mm (3–4 inches) in diameter by 150–200 mm (6–8 inches) in length, and high quality. Generally speaking, the difficulties found when growing large-sized crystals of lead-containing materials are their complex thermodynamic behavior and special physical properties. For example, common problems include incongruent melting and low thermal conductivity. The incongruent melting means that crystals cannot be grown from stoichiometric melts. The low thermal conductivity affects the transport of latent heat released during the crystallization process, thereby causing interface instability, defects, inclusions and phase segregation, etc. The difficulties here stemmed from a basic discrepancy between theoretical predictions and experimental data on the congruent behavior and the perovskite precipitation characteristics for the MPB solid solution systems associated with PT.

In addition, solid-state phase transformations commonly occur on cooling to room temperature that lead to twinning and possible cracking problems. Furthermore, the growth of lead-containing crystals at high temperatures encounters more special technical barriers, including:

• corrosion of container materials – platinum crucibles are attacked by lead-containing melt at temperatures above 1300 ºC, leading to severe leakage;

• high volatility of toxic PbO from the melt at high temperatures;

• difficulties in controlling compositional homogeneity for multi-component systems due to the compositional segregation.

The critical problems enumerated above make the growth of large PMN–PT crystals for commercialization a challenging task.

1.1.3 Growth of PMN–PT crystals from stoichiometric melt using the Bridgman ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Contributor contact details
• Introduction
• Part I: High-strain, high-performance piezo- and ferroelectric single crystals
• Part II: Field-induced effects and domain engineering
• Part III: Morphotropic phase boundary and related phenomena
• Part IV: High-power piezoelectric and microwave dielectric materials
• Part V: Nanoscale piezo- and ferroelectrics
• Part VI: Piezo- and ferroelectric films
• Part VII: Novel processing and new materials
• Part VIII: Novel properties of ferroelectrics and related materials
• Index