Piezo Ceramics
14 November 2008, 11:48
Categories: smt-energy-piezoelectric
The piezoelectric effect is a property that exists in many materials. The name combines piezo, which is derived from the Greek word for pressure, and electric from the Greek word for amber (static electricity generated by rubbing amber has been identified as the first known electric phenomenon). In a piezoelectric material, the application of a force or stress results in the development of a charge in the material. Conversely, the application of a charge to the same material will result in a change in mechanical dimensions or strain.
Several ceramic materials exhibit a piezoelectric effect. These include lead-zirconate-titanate (PZT), lead-titanate (PbTiO2), lead-zirconate (PbZrO3), and barium-titanate (BaTiO3). Strictly speaking, these ceramics are not actually piezoelectric but rather exhibit a polarized electrostrictive effect. A material must be formed as a single crystal to be truly piezoelectric. Ceramics have a multi-crystalline structure made up of large numbers of randomly orientated crystal grains.
Advanced Cerametrics Inc. (ACI) is producing PZT ceramic fibers and composite materials that generate ten times the amount of power from waste mechanical energy as other flexible forms of piezo materials. This functional amount of power can be used for self powering electronic loads, damping vibrations or morphing structures. Harvested mechanical energy (vibration, compression or flexure) can all be tapped to deliver extreme life span power in places previously impossible. An example is Head Sport tennis rackets and skis that include energy harvesting actuators made from ACI’s patented PZT fiber. These self-powered products dampen vibrations and deliver torsional stability created during a ball strike or edge chatter from a ski turn, by using the energy created to control the shape of the ski or racket.
Meanwhile, Noliac is producing piezogenerators that can be used as a compact source for electrical energy. Their ceramic multilayer generators are built up with a number of thin ceramic layers sandwiched between internal electrodes, resulting in a low output voltage but high current compared to conventional single layer piezoelectric generators. An example of a multilayer generator’s spec is:
• Multilayer generator size: 5×5x2 mm
• Thickness of active layers: 67 µm
• Applied force: 10 kN
• Generated energy: 12 mJ
• Generated voltage: 400V
Posted by: The Editors
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