Introduction
Piezoelectric ultrasonic transducers are critical components for many high-technology devices in many industries. For example, the ultrasonic body inspection device, the ultrasonic therapy device, the ultrasonic cleaner, and the ultrasonic non-destructive inspection device. All those important devices consist of piezo transducers using the piezoelectric effect.
1. The Piezoelectric Effect: Core Principle
The piezoelectric effect is a unique electric-mechanical phenomenon of certain solid materials. It mainly exists in two inter-convertible forms: the direct piezoelectric effect (mechanical stress inducing electric polarization and surface charge accumulation) and the converse piezoelectric effect (external electric field causing elastic deformation of materials). The piezoelectric effect essentially achieves the mutual conversion between physical (mechanical) energy and electrical energy.
Mechanical-to-electrical conversion:
Stress on the ceramic → Charge separation → Voltage output.
Used in sensors (e.g., pressure sensors, accelerometer)
Electrical-to-mechanical conversion:
Applied voltage → Ceramic deformation → Mechanical motion
Powers (e.g., Ultrasonic cleaner, Ultrasonic welder)
2. The piezoelectric ceramic
The piezoelectric ceramic is made of Lead zirconate titanate (PZT), lead titanate (PbTiO₃) and lead zirconate (PbZrO₃), and other common materials are barium titanate (BaTiO₃), sodium potassium niobate (KNN) and bismuth ferrite (BiFeO₃), because of its characteristic, The piezoceramic plays an important role in the piezoelectric effect for the mutual conversion between electrical energy and mechanical energy. It acts as an energy transducer, converting electrical signals into ultrasonic vibrations or converting mechanical vibrations into electrical signals in sensors.
In addition, it also used in piezoelectric transformers for voltage conversion and in touch sensors for signal detection, which are essential components in many devices.
3. The Piezoelectric Ultrasonic transducer
Single-element Piezoelectric Ceramic Transducers (Single-element UT Probe):
Structure: The single-element UT probe is consists of a single piezoelectric ceramic element (usually disc-shaped or cylindrical). The single-element piezoelectric acts as a signal sender and signal receiver.
Function: Suitable for low-power, general-purpose applications such as basic ultrasonic testing (e.g., detecting simple defects in small workpieces) and low-intensity ultrasonic cleaning. Its single ceramic element ensures stable vibration, but the ultrasonic beam is relatively wide, limiting detection resolution.
② Dual-element Piezoelectric Ceramic Transducers (Dual-element UT Probe):
Structure: The dual-element UT probe consists of two piezoelectric ceramic elements (usually disc-shaped or cylindrical), but there is a barrier between the two piezoelectric ceramics. One of the piezoelectric ceramics acts as a signal sender, and another one acts as a receiver for receiving the signal back to the device.
The structure is simple and compact.
Function: Suitable for high-power, precisely purposed applications such as high-resolution ultrasonic testing (e.g., detecting tiny defects in small workpieces). Its dual ceramic element ensures stable vibration, but the ultrasonic beam is relatively focused, with higher detection resolution.
③ Sandwich-type (laminated) piezoelectric ceramic transducers (ultrasonic transducers for cleaning/welding):
Structure: It adopts a laminated structure of "piezoelectric ceramic + metal electrode + elastic substrate" (e.g., bolt-clamped Langevin transducer, BLT). The piezoelectric ceramic elements are stacked and clamped by bolts, with electrodes alternately arranged between the sheets. This structure enhances mechanical strength and power capacity.
Function: Mainly used in high-power applications such as ultrasonic welding, ultrasonic drilling, and high-intensity ultrasonic cleaning. The laminated design improves the transducer's ability to withstand high power and mechanical stress, and the bolt clamping ensures stable operation under high-frequency vibration, avoiding ceramic sheet damage.
References
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