vibration mode of Piezoelectric ceramic

Piezoelectric ceramic is under the action of an external alternating electric field, the vibration sensor occurs to excite the ultrasonic piezoelectric ceramic,it is vibration mode flexural vibration and shear vibration, piezoelectric ceramic vibrator commonly is used for stretching vibration mode is divided into length vibration mode .The radial vibration mode and the thickness vibration mode show the thickness-stretching vibration mode of the wafer thickness. The piezoelectric plate sensor is a wafer-shaped polarization direction and the applied electric field is in parallel with the thickness direction. The vibrator vibrates go along the thickness direction. This vibration mode is fundamental resonance.

The frequency range is inversely proportional to the thickness. The applicable frequency range is 30~100 khZ. The relative bandwidth of piezoelectric sensor manufactuer is within the same. If two long thickness ceramic plates with the same thickness and polarization are glued together, one of them will be stretched when the external electric field is applied and the other is shortened. , It can be shown that the bending vibration occurs. The piezoelectric plate energy harvesting is bonded in the opposite direction and connected in series, showing the parallel connection of the two ceramic sheets with the same polarization direction in the two ceramic bonding. The electric field in the sheet can only stimulate one of them to generate bending vibration. Similarly, two piezoelectric ceramic sheets are bonded on a thin metal sheet or a ceramic sheet and a thin metal are used. Bonding together can also produce bending vibrations.

The relationship between the resonant frequency fr of the piezoelectric plate transducer vibration mode and the length Z of the sheet and the total thickness t of the adhesive sheet is a frequency constant, and the frequency range which the thickness bending vibration mode is applied is 500 to 100 khz. (W is the width of the piezo ceramic sheet) The thickness shear vibration mode is characterized in that the electrode surface is parallel to the polarization direction, and the ceramic sheet generates the shear vibration in the thickness direction under the action of the alternating electric field, and the thickness shear mode of piezoelectric plate bimorph is relatively easy to be excited. In the high frequency range of 10~60 khz, the piezoelectric transducer emits ultrasonic waves in an ultrasonic distance meter. The amplitude of the vibration of the oscillator is required to be large. Therefore, the use of the bending vibration mode is desirable. At the same time, since the acoustic impedance of air is extremely low, the general piezoelectric material cannot achieve impedance matching with it. Therefore, it must also be realized by means of the transition layer.