Applications Of Piezoelectric Ceramics

Piezoelectric ceramics are widely used due to their piezoelectric properties and the resulting diversity of electromechanical properties. Generally, these applications can be divided into two broad categories, namely as piezoelectric oscillators. When used as a piezoelectric resonator, piezoelectric ceramic materials are required to have good frequency, temperature stability and high mechanical quality factor Qwps79.jpg (Qwps80.jpg indicates the degree of internal energy consumption of the material during vibration conversion); when used as a transducer, it is required to have a high mechanical coupling coefficient K (wps81.jpg = mechanical conversion into electrical energy / input mechanical energy, or wps82.jpg = conversion of electrical energy into mechanical energy / input electrical energy) and the larger relative permittivity WPS83.jpg applications for piezoelectric ceramics are given below.
1. Piezoelectric ceramic igniter
This is a device that converts mechanical force into an electric spark to ignite a combustion, and is an electromechanical transducer. In 1958, the use of barium titanate (BaTiO picture keywords) ceramic piezoelectric effect for ignition, but this material ignition rate is not high, noisy, in 1962 began to trial lead zirconate titanate (PZT) piezoelectric ceramics to make ignition, this igniter is widely used in daily life, industrial production and military aspects, used to ignite gas and various explosives and rocket ignition detonation.
(1) Basic principles
The working process of the igniter is divided into three stages: high pressure generation, discharge ignition and ignition of combustible gas.
High voltage generation – Take a cylindrical piezoelectric ceramic element as an example, as shown in Figure 5-2. When the mechanical force F acts on the cylinder, the crystal is distorted, causing the center of positive and negative charges in the crystal to shift, resulting in a large accumulation of free charge on the upper and lower surfaces of the cylinder, resulting in a high-voltage output. The output voltage is:
where A - the cross-sectional area of the cylinder;
h - cylinder height;
Image keywords - piezoelectric voltage constant.
Discharge ignition – placing the piezoceramic element in a closed loop with an appropriate gap in which a discharge spark is generated when the voltage rises to the discharge voltage of this gap.
Ignite combustible gas - general fuel gas is not easy to burn, so ethane that is easy to vaporize is generally used. In order to extend the discharge time and prevent the spark from going out too quickly to improve the ignition rate, an appropriate resistor can be inserted in series at the discharge end.