Study yields new knowledge about materials for ultrasound and other applications

Piezoelectric materials turn mechanical stress into electrical energy, and vice versa. In 1997, researchers developed piezoelectric materials that were 10 times better at coupling electrical and mechanical responses than prior state-of-the-art materials. But even scientists did not understand why the newer materials were so responsive.
Now, scientists at the Department of Energy’s Oak Ridge National Laboratory and their research partners have used neutron scattering to discover the key to piezoelectric excellence in the newer materials, which are called relaxor-based ferroelectrics. (A ferroelectric material has electrical polarization that is reversed by application of an electric field.) Their findings may provide knowledge needed to accelerate the design of functional materials for diverse applications.
Relaxor-based oxide ferroelectrics have revolutionized piezoelectric devices. In medical ultrasound, for example, the mechanical pressure of sound waves generates images of a person’s interior. Compared with the performance of traditional materials, the stronger response of relaxor-based ferroelectrics yields a more detailed electrical signal that produces better images. Instead of having somewhat blurry guidance from 2D images to diagnose a cause of pain, assess prenatal condition, guide a biopsy or assess damage after a heart attack, doctors now rely on finely detailed 3D imagery. These modern materials also made it possible to focus ultrasound waves for non-invasive medical treatments of conditions such as tumours or gallstones. This technology passes individual beams harmlessly through tissue; the beams converge on a target where their effects are concentrated, like light passing through a magnifying glass to ignite paper.
‘We figured out at an atomic level why certain materials are so great at mechanically responding to an electric field by changing shape or size,’ said lead author Michael Manley of ORNL. ‘The finding provides a basis for high-performance actuators and sensors.’ Compared to traditional polycrystalline materials, the newer piezoelectric crystals generate a greater mechanical force in response to an applied electric field.

Oak Ridge National Laboratory