physical mechanism of the piezoelectric properties

The physical mechanism of piezo level sensor is the piezoelectric properties, we know that the polarization of the piezoelectric ceramic which will be bound at both ends of the charge, so the surface of the electrode is adsorbed a layer of free charge from the outside world. When an external pressure F piezoelectric generator is applied to the ceramic sheet, discharge occurs at both ends of the sheet, and in contrast, charging occurs due to a pulling force. This phenomenon of mechanical effect into electrical effect belongs to the positive piezoelectric effect. In addition, the piezoelectric ceramic has the property of spontaneous polarization, and the spontaneous polarization of ultrasonic plate transducer can change under the effect of the external electric field. Therefore, when an electric field is applied to a dielectric having a piezoelectric property, deformation occurs in the piezoelectric ceramic. However, the reason why the piezoelectric ceramics are distorted for piezo bimorph actuator .when the same external electric field as the spontaneous polarization is added, the polarization strength is equivalent to that. The increase of the polarization strength causes the piezoelectric ceramic sheet to elongate along the polarization direction. Conversely, if the reverse electric field is applied for piezoelectric sensor working .the piezo ceramic sheet is shortened in the direction of polarization. This phenomenon due to electrical effects into mechanical effects is inverse piezoelectric effect. At present, the low temperature is sintering methods.it is sol-ge l, hot pressing, ultra-fine powder preparation and flux method.The purpose of doping Li2O is to lower the sintering temperature. It was found that good piezoelectricity of piezo disc circuit was synthesized at low temperature of 950 ℃. The PMN-PNN-PZT piezoelectric ceramics had good piezoelectricity at 900 ℃. Performance improvement using doping fluxes is the most fundamental improvement, such as coprecipitation, salt dissolution, sol-gel method, hydrothermal method and so on.