A piezoelectric substance is a crystalline mineral which responds to a mechanical force by generating an electric charge.
The substance may be considered as a lattice of electric dipoles, which together form a polarized field. When the field undergoes mechanical stress, the field changes its polarization, either through a physical reconfiguration of the dipole lattice or a re-orientation of the dipole moments under stress. This is the piezoelectric effect.
Piezoelectric material (1) before poling, (2) after poling. Adapted from source: http://www.physikinstrumente.com/tutorial/4_15.html
The piezoelectric effect is reciprocal, meaning: A) a piezoelectric substance will respond to a mechanical force by generating an electric charge, and; B) it will respond to an electric field by generating a mechanical response. This latter response is called the inverse piezoelectric effect.
The piezoelectric effect and its inverse are also proportional. The voltage generated by the piezoelectric effect is proportional to: A) the amount of force applied, and; B) the type of force applied (i.e. tension and compression produce opposite polarities). Likewise, the mechanical response of the inverse piezoelectric effect is proportional to: A) the field's strength, and; B) the field’s polarity.
The piezoelectric effect is passive, and requires no additional power other than the mechanical or electric stimulus.
Applications (Aleksi)
http://www.youtube.com/watch?v=fHp95e-CwWQ
Piezoelectric materials:
Nowadays for the Piezoelectric sensing is mostly used ceramics. The earliest one was Titanate. The three most popular piezoelectric materials are Zinc oxide, Aluminum nitride and lead-zirconite-titanium oxides what is known as PZT.
Piezoelectric materials are usually sensitive to temperature changes. For example quartz looses sensitivity if the temperature drops with a slope of -0,016%/Celsius. With PVCF films and materials the sensitivity changes when the temperature is on the higher or lower side of 40 Celsius.
Piezoelectric materials are usually generated from high-purity metal oxides in form of fine powder (lead oxide, titanium oxide etc.).The powder is calcinated and mixed in a right proportion. Then it is mixed with solid and/or liquid organic binders to make a so called "cake" and heated in a controlled temperature. The material is covered with contact electrodes and poled. After this the piezoelectric material is shaped to its final shape.
New materials:
Modeling piezoelectric sensing:
As earlier we determined how piezoelectric will work and here is explanation how to determine a g-coefficent:
g_n_n = \frac{d_n_n}{\varepsilon_0\varepsilon_n_n} |
Determining the coefficent a voltage gradient:
\frac{V}{m}/\frac{V}{m^2} |
Determining other coefficent which h is determined:
\frac{V}{m}/\frac{V}{m} |
Piezoelectrical phenomenon is said in other words that it changes mechanical energy into electrical energy
It can be determined as the following:
coupling coefficents kmn is:
k_m_n = \sqrt{d_m_n \cdot h_m_n} |
The capacitance of piezoelectric can be determined by using the formula as below:
C = \kappa\varepsilon_0\frac{a}{l} |
where a is area and l is the crystal thickness
At last the output voltage can be calculated such as:
V = \frac{d_1_1}{C}F_x = \frac{d_1_1l}{\kappa \varepsilon_0a}F_x |
http://www.piceramic.com/piezo_effect.php
https://www.americanpiezo.com/knowledge-center/piezo-theory/piezoelectricity.html
http://en.wikipedia.org/wiki/Piezoelectricity
https://www.americanpiezo.com/piezo-theory/ceramics.html
https://www.americanpiezo.com/knowledge-center/piezo-theory/new-materials.html
Jacob Fraden: Handbook of Modern Sensors (Physics, Designs and Applications), Fourth Edition, Springer