Parameters of piezoelectric material

Piezoelectric ceramic materials have piezoelectric properties, not only have physical and mechanical properties, but also have piezoelectric properties. The parameters that generally describe the piezoelectric properties,it is frequency constant N, piezoelectric coefficient, electromechanica coefficient , mechanical quality factor, and curie point temperature.

 (l) Piezoelectric constant, the vibration mode of the piezo tube download is large, only the stretching vibration is considered, it is the vibration sensor of the piezoelectric material.Dynamic modes include thickness vibration, length vibration, and radial vibration. Where the frequency constant is the determined piezoelectric body.Dimensions in the direction of vibration (thickness vibration mode, length stretching vibration, radial vibration.The time is the production of the diameter and the resonant frequency of the material as it reaches resonance. Because medical ultrasound transducers are generally only tested.Considering the thickness vibration mode can be expressed.

(2) About piezoelectric coefficient, piezoelectric coefficient is a description of the mutual conversion between electrical energy ,mechanical energy and mutual misfortune. Usually the piezoelectric coefficient is determined by the piezoelectric stress coefficient e, the piezoelectric strain coefficient d and the piezoelectric electricity.The pressure coefficient g and the piezoelectric effect ultrasound piezo stiffness coefficient h are represented by four parameters. the piezoelectric stress coefficient e can be expressed.

When the electric field changes 0, the amount of change in stress required per unit strain; or  the change in stress caused by the change in unit electric field strength. The piezoelectric strain coefficient d is the change in strain caused in the electric field strength when the stress of the piezoelectric material changes . That is, when the piezoelectric material stress changes. The change in strain caused by the change in the unit electric displacement; it may also indicate the change in the electric field strength caused by the change in the unit stress when the electric displacement changes zero.

When the strain change is zero, the change in the stress caused by the change in the electric displacement; or the change in the electric field strength caused by the unit strain when the electric displacement changes to zero. The four physical quantities of piezoelectric stress coefficient e, piezoelectric strain coefficient d, piezoelectric voltage coefficient g and piezoelectric stiffness coefficient h can be divided into two groups according to the characteristics of the  transmitting and receiving Piezo ceramics for medical device.which describes the change .The emission characteristic of the energy device is called the transmission coefficient; It describes the receiving characteristic of the transducer called the receiving coefficient.

(3) About electromechanical coincidence coefficient K, buy HIFU piezo ceramics the ability of piezoelectric materials to convert electrical energy and mechanical energy. And for the transduction.the size of the electromechanical cohesion coefficient also affects its sensitivity. In general, the more electromechanical cohesion coefficient has large piezoelectric materials, the smaller is the loss of converted electrical energy and mechanical energy, so the sensitivity of the fabricated transducer is higher.

(4) About mechanical quality factor Q , the amount mechanical is loss of piezoceramic materials piezos discs sensor during vibration. The coefficient and mechanical loss is the greater the mechanical quality factor, the smaller is the energy of the internal friction loss when it resonates; on the contrary, When the mechanical quality factor is small, the mechanical loss is greater and the energy attenuation is faster. At the same time, the mechanical quality factor is also an important parameter that determines the final transducer bandwidth.