Improved ceramic harvests electricity from vibrational energy

Dance floors, gyms and engines could all contribute.

Some organisations have already begun to harvest electricity from waste vibrations to power lights and recharge batteries using a class of piezoelectric ceramic materials.

Now, a team led by materials scientists at Penn State University, USA, has expanded these early efforts of energy harvesting by improving the structure and chemistry of a piezoelectric material made of potassium sodium niobate, or KNN. The improved ceramic samples are reportedly thermally stable and fatigue resistant.

First author Aman Nanda, a doctoral student in materials science and engineering at Penn State, highlights the lightweight design of the KNN material, and notes ‘we could also include them in aircraft — which wasn’t previously possible with lead-based materials — to harvest the vibrations during flights, even at high altitudes.’

Another advantage is that lead-free materials are biocompatible, opening up the possibility of use in biomedical applications, such as self-powered pacemakers.

According to Nada, energy harvesters have a cantilever design, where a stiff element is fixed on one end and unattached on the other. As ceramic materials are brittle, special care and device designs are needed to apply them in real applications to handle mechanical stress. When pressed, the cantilever vibrates and generates electricity through the piezoelectric effect of the material that converts mechanical energy into power.

To replace lead and produce a more lightweight piezoelectric ceramic, the researchers systematically modified the structure and chemistry of KNN. They first added a magnetic material, manganese, to its chemical composition. Then they adjusted the grain growth, or the size of individual crystals within the microstructure, through heat treatment.

Co-corresponding author Professor Mike Lanagan comments, ‘These materials have been around a while in terms of chemistry, but [Nada] has done a lot more work in making the chemistries better by changing the composition and synthesis procedures, such as experimenting with different heat times, temperatures and structures of the material.’

Nada’s work resulted in unidirectional grain growth, which enhances functional properties, as well as improved piezoelectric response. The research is published in the journal Small.