Piezoelectric ceramics produce an electrical charge when a load is applied and deformation occurs. Piezoelectric ceramics can also produce force or deformation when an electrical charge is applied. The production of an electrical charge is useful in pressure or load sensing applications. The production of force or deformation is useful in microactuators, nanoactuators or piezoelectric motors.
Piezoelectric ceramics consist of ferroelectric materials and quartz. Ferroelectric materials include barium titanate, bismuth titanate, lead magnesium niobate, lead metaniobate, lead nickel niobate, lead zinc titanates (PZT), lead-lanthanum zirconate titanate (PLZT) and niobium-lead zirconate titanate (PNZT). Important parameters for piezoelectric ceramics include electromechanical coupling constant, distortion or charge constant, mechanical dielectric constant (relative permittivity), loss tangent, electrical resistivity, and curie temperature.
Barium titanates and bismuth titanates are common types of piezoelectric ceramics Modified barium-titanate compositions combine high-voltage sensitivity with temperatures in the range of -10° C to 60° C. Barium titanate piezoelectric ceramics are useful for hydrophones and other receiving devices. These piezoelectric ceramics are also used in low-power projectors. Bismuth titanates are used in high temperature applications, such as pressure sensors and accelerometers. Bismuth titanate belongs to the group of sillenite structure-based ceramics (Bi12MO20 where M=Si, Ge, Ti).
Lead magnesium niobates, lead metaniobate, and lead nickel niobate materials are used in some piezoelectric ceramics. Lead magnesium niobate exhibits an electrostrictive or relaxor behavior where strain varies non-linearly. These piezoelectric ceramics are used in hydrophones, actuators, receivers, projectors, sonar transducers, and in micro-positioning devices because they exhibit properties not usually present in other types of piezoelectric ceramics. Lead magnesium niobate also has negligible aging, a wide range of operating temperatures and a low dielectric constant. Like lead magnesium niobate, lead nickel niobate may exhibit electrostrictive or relaxor behaviors where strain varies non-linearly.
Piezoelectric ceramics include PZN, PLZT, and PNZT. PZN ceramic materials are zinc-modified, lead niobate compositions that exhibit electrostrictive or relaxor behavior when non-linear strain occurs. The relaxor piezoelectric ceramic materials exhibit a high-dielectric constant over a range of temperatures during the transition from the ferroelectric phase to the paraelectric phase. PLZT piezoelectric ceramics were developed for moderate power applications, but can also be used in ultrasonic applications. PLZT materials are formed by adding lanthanum ions to a PZT composition. PNZT ceramic materials are formed by adding niobium ions to a PZT composition. PNZT ceramic materials are applied in high-sensitivity applications such as hydrophones, sounders and loudspeakers.
Piezoelectric ceramics include quartz, which is available in mined-mineral form and man-made fused quartz forms. Fused quartz is a high-purity, crystalline form of silica used in specialized applications such as semiconductor wafer boats, furnace tubes, bell jars or quartzware, silicon melt crucibles, high-performance materials, and high-temperature products. Piezoelectric ceramics such as single-crystal quartz are also available.
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Electroceramics are ceramic materials that have been specially formulated for specific electrical, electro-magnetic, or optical properties. They include dielectric ceramics, electrostrictive ceramics, ferrite ceramics, garnets (ferromagnets), and piezoelectric ceramics.