An alternating current will have a depolarizing effect during each half cycle in which polarity is opposite that of the polarizing field. The degree of depolarization depends on the grade of material, the exposure time, the temperature, and other factors, but fields of 200-500 V / mm or greater typically have a significant depolarizing effect. Mishandling the element by exceeding its electrical, mechanical, or thermal limitations can accelerate this inherent process.Įlectrical Limitations - Exposure to a strong electric field, of polarity opposite that of the polarizing field, will depolarize a piezoelectric material. Exact rates of aging depend on the composition of the ceramic element and the manufacturing process used to prepare it. Stability- Most properties of a piezoelectric ceramic element erode gradually, in a logarithmic relationship with time after polarization. Dielectric losses usually are more significant than mechanical losses. Dielectric losses and mechanical losses also affect the efficiency of energy conversion. k depends on the mode of vibration and the shape of the ceramic element. The values for minimum impedance frequency and maximum impedance frequency can be used to calculate the electromechanical coupling factor, k, an indicator of the effectiveness with which a piezoelectric material converts electrical energy into mechanical energy or mechanical energy into electrical energy. These frequencies are determined by experiment - to see how, refer to Determining Resonance Frequency. As the frequency is further increased, impedance increases to a maximum (minimum admittance), which also is the anti-resonance frequency. This frequency also is the resonance frequency. The frequency at which the element vibrates most readily in response to the electrical input, and most efficiently converts the electrical energy input into mechanical energy - the resonance frequency - is determined by the composition of the ceramic material and by the shape and volume of the element.Īs the frequency of cycling is increased, the element's oscillations first approach a frequency at which impedance is minimum (maximum admittance). S: strain (change in height / original height of element)Ī piezoelectric ceramic element exposed to an alternating electric field changes dimensions cyclically, at the frequency of the field. Δh: change in height (thickness) of ceramic element Where l: initial length of ceramic element The relationships between an applied voltage or electric field and the corresponding increase or decrease in a piezoelectric ceramic element's thickness, length, or width are: Please contact a BeStar representative with your specific application questions.Behavior of a Piezo Element Influence of Input FrequencyĪt low input frequencies, the relationships between a force applied to a piezoelectric ceramic element and the electric field or charge produced by the piezo element are: We have additional information about the piezo element and piezo technology in our special Piezo Element Catalog, which can be found under the resources tab. When combined with a plastic cone, or when layered in a bimorph configuration, the piezo disc can be a very powerful sound producer. The piezo disc is a low cost, low power consumption solution for creating good sound output at specific mid and high range frequencies. Future directions include actuators and even piezo speakers. The BeStar piezo element provides performance in both sonic and ultrasonic applications and has found uses in applications beyond piezo buzzers for ultrasonic atomization, or as an impulser. By doping the PZT material, its piezoelectric characteristics can be modified: especially the hardness or softness of the material. This element is designed so that the mechanical resonant frequency matches the frequency of the driving signal. PZT ceramic material is used as the piezoelectric element. The metal diaphragm is usually brass, stainless steel or nickel alloy, thickness less than 0.5 mm.

This causes the piezo diaphragms to bend, producing sound waves. When AC voltage is applied across the electrodes of the piezoelectric ceramic it expands and contracts at the frequency applied. The basic element in all of these is a piezoelectric ceramic mounted on a metal diaphragm. Specially formulated piezo ceramic discs are applied to a variety of base disc materials in order to suit most applications. BeStar has special expertise in piezo element production from very small units for sensors, to very large units for sirens. Also called Piezo Diaphragms and Piezo Benders, essentially it is offered so that product manufacturers can produce sound within their own housing/enclosure designs. The Piezo Element is the heart of a Piezo Buzzer.

Piezoelectric element