Advanced Piezoelectric Materials, Specific Characteristics
Thermal expansion example with piezo ceramic material PIC 255
- The thermal strain exhibits different behavior in the polarization direction and perpendicular to it.
- The preferred orientation of the domains in a polarized PZT body leads to an anisotropy. This is the cause of the varying thermal expansion behavior.
- Non-polarized piezo ceramic is isotropic. The coefficient ofexpansion is approximately linear with a CTE of approx. 2 x 106/ K.
- The effect of successive temperature changes must be given particular consideration in the application. Large changes in the curve can occur especially in the first temperature cycle.
- Depending on the material, it is possible that the curves deviate substantially from those illustrated.
Parameter stability at high temperatures: example with piezo material PIC 300
- PIC 300 is suitable for use at temperatures up to 250 °C (for short durations, to 300 °C).
- The drift of the measured value for the coupling factor and the capacitance can be significantly reduced by burn-in of over 12 h at 300 °C.
- The expected percentage changes are shown in diagrams A and B.
- PIC 300 capacitance exhibits a low temperature dependency in the temperature range up to 250 °C (Diagram C).
Deformation behavior example with piezo ceramic material PIC 255
- In the case of large-signal fields (max. 2 kV/mm), the strain of a piezoceramic is associated with reversible and irreversible domain reorientation processes.
- The domain reorientations cause larger deformations in the ceramic elements than can be calculated from the piezo coefficients given in the table (small-signal values).
- The irreversible domain reorientations lead to hysteresis in the strain behavior.