Vibration mode of piezoelectric ceramics vibrator

Piezoelectric ceramic vibrators have a wide range of applications. Piezoelectric ceramic transformers and piezoelectric ceramic filters are processed or combined by piezoelectric vibrators in a certain way. The parameters of the piezoelectric ceramics transducer depends largely on the vibration of the piezoelectric vibrators. mode. The vibration modes of the vibrator are divided into: telescopic vibration, bending vibration, shear vibration and telescopic vibration mode. The conventional stretching vibration mode of the piezoelectric ceramic vibrator is further divided into a longitudinal stretching vibration mode, a radial vibration mode, and a thickness direction vibration mode.

1. Thin long piece length stretching vibration mode

   
       The so-called thin long piece means that the length l of the PZT material parameter is much larger than the width w and the thickness t, and the width w is much larger than the thickness t. Both ends of the ceramic piece are in a state of mechanical free vibration. Under the action of an applied alternating electric field, the thin long piece produces stretching vibration along the length direction. Due to the vibration, the vibration direction of each point in the sheet coincides with the propagation direction, so the vibration wave is a longitudinal wave, and the amplitude of the center point of the film is zero, and the amplitude of both ends is the largest. The entire length of the film accommodates only the fundamental and half wavelengths. The fundamental resonant frequency is:

Radial vibration mode of thin disc.

A thin wafer is a wafer having a diameter D that is much larger than the thickness t of piezo ceramic ring transducer. The stretching vibration along the diameter direction of the wafer is called the radial vibration mode. The polarization direction is parallel to the thickness direction, and the vibration direction is parallel to the radial direction of the wafer. The vibration direction is consistent with the wave propagation direction, and the vibration wave is a longitudinal wave. The amplitude of the center of the wafer is zero, which is the node of the wave, and the wavefront is a cylindrical surface. If the wafer is divided by a ring electrode, high-order overtone vibration will occur, and its vibration frequency is about 2.8 times higher than that of the whole electrode. Piezoelectric ceramic vibrators using this overtone vibration mode of piezoelectric transducer ring can be used to load higher frequency filters.

 Disc thickness vibration mode

This mode of vibration requires a ratio of the diameter D of the piezo wafer to the thickness t. This vibration mode is suitable for a frequency range of 3 to 10 MHz and a relative bandwidth of 1 to 4%.