Barium titanate ceramics piezoelectric properties

Barium titanate has many important commercial apphcations. It has both ferroelectric and piezoelectric properties. Also, it has a very high dielectric constant (about 1,000 times that of water). The compound has five crystalline modifications, each of which is stable over a particular temperature range. Ceramic bodies of barium titanate find wide applications in dielectric amplifiers, magnetic amplifiers, and capacitors. These storage devices are used in digital calculators, radio and television sets, ultrasonic apparatus, crystal microphone and telephone, sonar equipment, and many other electronic devices. 

Ferroelectric ceramics (such as barium titanate, lead zircanate titanate) Sensors and actuators, electronic memory, optical applications Tape casting, sputtering, pressing, templated grain growth Improved dielectric and piezoelectric properties... 

Piezoelectricity links the fields of electricity and acoustics. Piezoelectric materials are key components in acoustic transducers such as microphones, loudspeakers, transmitters, burglar alarms and submarine detectors. The Curie brothers [7] in 1880 first observed the phenomenon in quartz crystals. Langevin [8] in 1916 first reported the application of piezoelectrics to acoustics. He used piezoelectric quartz crystals in an ultrasonic sending and detection system - a forerunner to present day sonar systems. Subsequently, other materials with piezoelectric properties were discovered. These included the crystal Rochelle salt [9], the ceramics lead barium titanate/zirconate (pzt) and barium titanate [10] and the polymer poly(vinylidene fluoride) [11]. Other polymers such as nylon 11 [12], poly(vinyl chloride) [13] and poly (vinyl fluoride) [14] exhibit piezoelectric behavior, but to a much smaller extent. Strain constants characterize the piezoelectric response. These relate a vector quantity, the electrical field, to a tensor quantity, the mechanical stress (or strain). In this convention, the film orientation direction is denoted by 1, the width by 2 and the thickness by 3. Thus, the piezoelectric strain constant dl3 refers to a polymer film held in the orientation direction with the electrical field applied parallel to the thickness or 3 direction. The requirements for observing piezoelectricity in materials are a non-symmetric unit cell and a net dipole movement in the structure. There are 32-point groups, but only 30 of these have non-symmetric unit cells and are therefore capable of exhibiting piezoelectricity. Further, only 10 out of these twenty point groups exhibit both piezoelectricity and pyroelectricity. The piezoelectric strain constant, d, is related to the piezoelectric stress coefficient, g, by... 

Barium titanate is a crystalline ceramic compound with outstanding diaelectric, piezoelectric, and ferroelectric properties. It is used in capacitors and as a piezoelectric transducer. 

Singh, K.C. and Nath, A.K. (2011) Barium titanate nanoparticles produced by planetary ball milling and piezoelectric properties of corresponding ceramics. Mater. Lett, 65 (6), 970-973. 

Thin film ceramic materials with important magnetic, optical, electronic, and mechanical properties are often highly anisotropic. Thus, the ability to control orientation is critically important in thin film applications. For many of the oxide materials, as well as Ae ionic materials, aqueous solution or sol-gel routes are the most convenient or the only method of preparation. Examples of these include barium titanate (BaTiOs) used in multilayer capacitors, lead-zirconate-titanate (Pb(Zr,Ti)03, "PZT") used as a piezoelectric material, and zinc oxide (ZnO) used in varistors. Thus, the use of substrates to control orientation can eliminate major problems in deposition of thin films. In some cases, e.g., the many magnetic and non-magnetic phases of iron oxide, the ability to control the phase formed is critical to production of the desired properties. While this can be controlled by solution conditions, the proper surface can add an additional and very effective mechanism of control. 

Ceramics as Dielectrics Barium titanate is used as a miniature capacitor because of its dielectric properties, which include ferroelectric-ity and piezoelectricity. Figure 1.7 shows ceramic piezoelectric parts and assemblies. 

Piezoelectric ceramic materials include titanates of barium and lead (BaTiOj and PbTiOj), lead zirconate (PbZr03), lead zirconate-titanate (PZT) [Pb(Zr,1i)03], and potassium niobate (KNb03). This property is characteristic of materials having comph-cated crystal structures with a low degree of symmetry. The piezoelectric behavior of a polycrystalline specimen may be improved by heating above its Curie temperature and then cooling to room temperature in a strong electric field. 

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