Thick-film piezoceramics and devices

Abstract

Over the past 20 years, thick-film (screen printed) technology has been shown to possess a variety of desirable characteristics, which are particularly suitable for the realisation of micro-sensors and actuators. In particular, thick-film sensors are noted for their robust, versatile, compact and inexpensive nature. This paper will describe how screen printed thick-films can be used as the basis for a variety of piezoelectric a transducers. It will be shown how the technology can be combined with MicroElectroMechanical Systems (MEMS) to generate new types of microengineered structure. The evolution of the technology to a successful enabling mechanism for modern-day solid state sensors is described. The paper begins with a brief overview of piezoelectric thick-films including a discussion of the main factors relating to paste formulation, characterisation and techniques for fabricating devices. There is also a description of methods for fabricating thick-films on silicon, which opens up the possibility of using thick-film technology in the field of MEMS. A number of specific sensors and actuators are described, including accelerometers, micropumps, ultrasonic motors, slip sensors for prosthetic hands, resonators, elastic wave sensors and ultrasonic separators.

Electrical properties of Li doped sodium potassium niobate thick films prepared by a tape casting process

“…It has been observed in PZT thick films that substrate clamping effect introduced stresses in the films, which distorted the unit cells and thus decreased the effectiveness of polarization process. It is important to recognize the significance of the clamping effect when citing piezoelectric data [25]. Therefore, it is typical to use d 33 values as piezoelectric constants to characterize thick-films so as to differentiate them from bulk ceramics.…”

Preparation and characterization of sol–gel derived sodium–potassium bismuth titanate powders and thick films deposited by screen printing

“…Most recently, piezoelectric thick films with thickness in the range of 10-100 m have attracted significant attention. They have been widely applied to micropumps, ultrasonic motors, resonators, microfluidic separators, high frequency transducers, and energy harvesting [16,17], because they exhibit properties such as larger displacement and quick response, high frequency, and can be precisely controlled [17]. However, the thick films are difficult to produce using lapping and machining bulk ceramics due to the expense, waste and difficulty in handling the ceramics, on the other hand, most of the thin film processing, such as sol-gel, sputtering, physical vapour deposition, chemical vapour deposition, and pulsed laser deposition are not practical due to the slow deposition rates and high levels of stress generated during processing which can lead to cracking of the film [18].…”

A credit card sized self powered smart sensor node

“…The substrate thickness is 110 m. The screen printing process requires materials to be mixed into a paste form. The lead zirconate titanate (PZT) printable paste used in this work was based upon a piezoelectric ink formed by blending PZT-5H powders of different particle size [28]. The blend of sizes results in an improved film density which, when combined with optimized processing parameters, give a substantially improved d 33 coefficient of 131 pC/N.…”