High-Temperature Piezoelectric Accelerometers – Simplified
Being able to increase the operating temperatures for actuators is highly important to expand the number of applications in which they can be deployed. It unlocks the potential to use those devices within an industry that uses machinery at the extremes of temperature such as aerospace, oil and gas, mining and energy. At the core of the most precise actuator designs is a piezoelectric ceramic, and it is this material which often determines the maximum operating temperature of the actuator. This blog provides details of potential piezoceramic materials for high temperature actuators.
What is an actuator?
First, let’s quickly look at what an actuator is. An actuator is a mechanism for controlled movement. In other words, a valve to a machine that has the ability to control the flow of whatever is moving through it, it can stop the flow, allow the flow to go through it or hold it somewhere in between. Different methods of actuation exist such as mechanical, magnetic, piezoelectric and hydraulic. All are powered differently (eg. pneumatic or electric) and use different types of pressure to move (eg. air, fluid or magnetic).
What is a piezoelectric actuator and why use it?
When a piezoelectric material is subject to a mechanical strain a voltage is produced, this is known as the piezoelectric effect. This effect can be reversed – when the piezoelectric materials are subjected to a voltage, a change in shape / mechanical displacement is produced and is known as the ‘inverse piezoelectric effect’ which is the foundations of what an actuator is. This property of piezoceramics can be harnessed for precise positioning on actuation, something that can be highly important within applications like miniaturized medical devices or even down-hole drill control. A piezoelectric actuator can be comparatively more beneficial to use due to the high resolution, quick response times, large force generation and low power requirements.
Lead Zirconium Titanate (PZT) is one of the key piezoelectric materials used for actuators. PZT is known within the field as a staple material for actuators and has already found use for automotive, printing, and medical applications. For stack actuators operating at high powers, self-heating is a significant issue for the PZT material which limits the maximum operating temperature to around 200°C. Combined with environmental sources of heat, this makes PZT based actuators limited in applications where they can be worked and increasing the operating temperature is something that Ionix has been working towards.
High temperature piezoelectric materials that have a Curie temperature, the point where they stop being piezoelectric, that is higher than 400 oC are usually high in production costs, low in mechanical strength and generally deliver low piezoelectric activity, such as bismuth titanate. Only one class of materials combines the high Curie temperature and high piezoelectric activity, >100 pC/N. This material is known as HPZ and is applied in many high temperature and challenging applications. It is an excellent candidate for the next generation of high temperature actuators.
HPZ High Temperature Stack Actuator
Piezoelectric ceramics are often stacked to produce higher strain actuators with larger potential displacements. The Ionix HPZ material is ideal for this kind of assembly as it has a high toughness to be able to withstand the required pre-loads while also having a very high strain to failure – allowing the actuating crystal to create more displacement. Combined with it’s high Curie temperature, this makes Ionix HPZ an ideal candidate for actuators which require a high operating temperature due either to internal heat generation during operation or due to environmental conditions.
A stack actuator was recently fabricated using Ionix HPZ material. It displayed excellent performance and a linear response beyond 400°C. Combined with compatibility with the same assembly processes as used for PZT, this demonstrates the application of HPZ as a potential solution for high temperature actuators.
Ionix HPZ material is available to buy from Ionix now as either ceramics, sub-assemblies or complete sensors. Ionix also offers support for the integration of HPZ into your sensors and actuators to minimise development time and costs.
Get in touch today if you’d like to level up your actuators with Ionix HPZ.