Help for understand of spontaneous polarization in piezo

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SUMMARY

This discussion centers on the concept of spontaneous polarization in piezoelectric materials, specifically addressing the confusion surrounding the behavior of a piezo disk under no applied stress. The user notes that piezo materials require poling under high temperature and electric fields, yet questions arise regarding the electric displacement (D) in the absence of external stress. The constitutive equation D = εE + dT indicates that D should equal the spontaneous polarization (P0) even when E and T are zero, leading to a contradiction in understanding. Clarification on this topic is essential for proper application of piezoelectric principles.

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  • Understanding of piezoelectric materials and their properties
  • Familiarity with the poling process in piezo materials
  • Knowledge of the constitutive equations related to piezoelectricity
  • Basic principles of electric displacement and polarization
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  • Research the effects of poling on piezoelectric materials
  • Study the relationship between electric displacement (D) and spontaneous polarization (P0)
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  • Explore advanced piezoelectric constitutive equations and their implications
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Researchers, materials scientists, and engineers working with piezoelectric materials, particularly those involved in the design and application of piezo devices in various fields.

athosanian
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dear all, I want to confirm whether there is spontaneous polarization in the piezo materials. I know the piezo materials need to be poled under high temperature and electric field before applications. So if there is spontaneous polarization, comes my following confusing.
Given a piezo disk with polarization along the thickness direction, with upper and bottom surface silver coated as electrodes. the spontaneous polarization of piezo disk is denoted as P0. When disk is in such a state, without any stress applied on it and the upper and bottom electrodes are connected. Then the stress and electric field in the piezo disk is zero. so from the constitutive equation:
　　　　　 D=ε*E+d*T
(where D is electric displacement, ε is electric permittivity, E is electric field, d is piezoelectric coefficient and T is stress.), the D is 0 in the piezo disk in such a state. However, because of spontaneous polarization in the piezo disk the D should not be 0, it should be P0 ! What is wrong with my thought? I hope some help. Thanks!
 
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