Tuesday, December 9, 2008
Piezoelectric ceramics exhibit strong electro-mechanical properties. Lead zirconium titanate (PZT) is a crystalline material that is commonly used to construct these ceramic devices. It can be shaped into thin discs and rectangular slabs. A sinusoidal driving voltage applied to a PZT crystal will cause it to compress and expand. This produces a mechanical wave that moves through the material at the velocity of sound of that material. The disc or slab geometry will produce strong resonance modes which can be exploited to construct electronic resonators and transducers.
A fundamental resonance mode for a thin disc is called the radial or ‘breathing’ mode, where the crystal expands and contracts from the centre node. Another mode is called the thickness expansion mode which occurs at a half wavelength resonance through the thickness of the crystal. Also for rectangular structures, there are even more resonant modes. Ceramic resonators exhibit moderate Q factors (500 to 2000) and frequency tolerance (0.5% to 2.0%), but they are smaller and less inexpensive than quartz crystals.
Labels: pzt transducer