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. (Credit: Nanowerk.com)
Nanowerk.com reports that materials engineers at the University of Leeds are investigating potassium sodium bismuth titanate (KNBT) as a lead-free ceramic piezoelectric materials that might substitute for Pb-containing materials, such as lead zirconium titanate (PZT).
They engineers say KNBT shows many of the necessary electrical and chemical properties of an adequate replacement for PZT. Further, they say it is lightweight and usable at room temperature.
Tim Comyn, lead investigator on the project, said, “These results are very encouraging. 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.”
Indeed, there has been a scramble over the past few years to find lead-free piezo materials ever since the European community enacted regulations that ban the use of most lead-containing materials in electronic and electrical devices.
According to a press release from the university, the researchers had great success using the U.K.’s Diamond Light Source synchrotron to investigate the structure and properties of piezoelectric ceramics to develop more lead-free PZT. “With the ‘Extreme Conditions’ beamline at Diamond we were able to probe the interior of the [KNBT] to learn more about its piezoelectric properties. We could see the changes in crystal structure actually happening while we applied the electric field,” says Comyn.
While acknowledging that PZT is the best material for the job at the moment, Adam Royles, a Ph.D. student on the project, he has high hopes for KNBT. “This could make it an ideal choice for many applications,” he says.
Their research has been published this month in Applied Physics Letters.
Comyn has coauthored several papers on piezoelectrics in ACerS journals, including the recent “Electron Backscattered Diffraction of MonoCrystalline Bismuth Titanate” and “Dielectric and Piezoelectric Properties in the System: (1-x)[(Na0.5K0.5NbO3)0.93-(LiTaO3)0.07]-x[BiScO3].”