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.

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