Non-PZT Ceramic Compositions

Except PZT there are several ceramic materials, which are commercially available and used in applications mainly for their high Curie temperature. These materials can be classified into several stractural classes (for material properties see Table 7.16.)  

Property Pz34 doped PbTiOs Pz35 lead metaniobate Pz46 bismuth titanate BaTiOs ceramics 

Some of the piezoeleetric materials are being used in applieations in the form of thin films of various thieknesses. The physieal situation is somewhat different from bulk materials. For example the electrode layer thickness is of comparable size with the thickness of piezoelectrically active film. If the film is deposited on the substrate the mechanical clamping is significant. Clamping could influence the film effective properties and the domain stracture for ferroelectric substances. Material coefficients are not usually completely available in the hterature because of the specific geometry and they depend on film thickness. Material properties of thin films are different from the bulk properties of the same material. Especially the size effect could result in loss of ferroelectricity below certain film thickness. Lower limit for the ferroelectricity is not generally known for all materials. 

There are basically two material classes used in thin films mostly for ultrasound transducers or for surface acoustic wave (SAW) applications. They are  

SrBi2Ti209 (SBT) thin films are studied for applicatiorrs in capacitors with high fatigue resistance, long polarization retentiorr, no polarization fatigue up to 10  

---