The researchers from the Institute for Materials Research at the University of Leeds' Faculty of Engineering have published their results in
Applied Physics Letters.
The team is using Diamond Light Source, a UK based synchrotron facility to investigate the structure and properties of piezoelectric ceramics in order to develop more environmentally friendly alternatives to the widely used but toxic ceramic crystal lead zirconium titanate (PZT).
Using the I15 Extreme Conditions beamline at Diamond, the researchers probed the interior crystal structure of the ceramics with a high energy pinpoint X-ray beam and saw changes in the crystal structure as an electric field was applied. Dr Tim Comyn, lead investigator on the project says the results demonstrate that this new material, potassium sodium bismuth titanate (KNBT), has the potential to perform the same job as its lead counterpart.
"These results are very encouraging," said Dr Comyn. "Although harmless when in use, at the end of their lifetime these PZT gadgets have to be carefully disposed of due to their lead content and as a consequence, there is significant interest in developing lead free ceramics."
Piezoelectric materials generate an electrical field when pressure is applied, and vice versa. For example in gas igniters, such as those used on ovens and fires, a piezoelectric crystal creates sparks when hit with the hammer. In an electrical field, it undergoes a phase transition, that causes changes in the crystal structure.
The team will continue to work at Diamond to study the electric field induced transformation at high speed (1000times per second) and under various conditions using state of the art detectors.
Adam Royles, PhD student on the project, added: "Not only could a lead free solution mean safer disposal of electronic equipment, by virtue of the absence of lead, these new materials are far lighter than PZT. The piezoelectric market has applications in many fields, where a lighter lead free alternative could make quite a difference."
Crystal structure of KNBT before the application of an electric field. The purple spheres are either sodium or potassium atoms, the red spheres are oxygen atoms, the small blue sphere is titanium. The figure shows the arrangement of the atoms in a rhombohedral structure, where the a, b and c axes are of the same length and rhombohedral angle is less than 90.
Crystal structure of KNBT after the application of an electric field. The purple spheres are either sodium or potassium atoms, the red spheres are oxygen atoms, the small blue sphere is titanium. The figure shows the arrangement of the atoms changed into tetragonal symmetry, where the a and b axes are of the same length and the c axis is longer.
