We all know that Soft PZT has superior d-coefficent aka piezoelectric charge coefficient. This means that a soft PZT element will exhibit more displacement for a given drive voltage( off-resonance). It will also produce more charge than hard PZT, given a specified load.

So is soft PZT better than hard PZT for off-resonance actuator applications? And if so, by how much?

Comparing a hard PZT and a soft PZT, we can find that the d coefficient is roughly twice as large. However, the d coefficient as a actuator only relates to a piezoelectric element by itself – not bonded to an external structure. Its like saying a Ferrari is fast car, but can it tow a trailer? In order to understand how much a piezo material can “tow”, you need to look at the compliance.

Hard PZT has a lower compliance (higher stiffness) than soft PZT. What this ends up meaning is that the performance gap between hard PZT and soft PZT in terms of an off-resonance actuator becomes less when considering the compliance. 

This can be accomplished via d33/s33^E. For this ratio, soft PZT is only 1.6x better than hard PZT, not 2x. Please see my videos on piezoelectric actuators, blocking force, and the piezoelectric stress coefficient here: https://www.learnpiezo.com/lectures#lecture7

Please let me know if you have questions and comments on this topic at husain@ultrasonicadvisors.com. Also please send your colleagues this email and ask them to subscribe if you think they would benefit from these emails. This is the subscription link: [Link to subscribe] 

Regards, 

Husain Shekhani, PhD 

Ultrasonic Advisors

husain@ultrasonicadvisors.com