The material, an erbium-doped lead magnesium niobium titanate (PMNPT) ceramic, shows an exceptionally large degree of deformation under a low electric driving field. The low electric driving field also reduces the risk of electrical breakdown of the piezoelectric material, potentially reducing failure rates and increasing the lifespan of piezoelectric components.
Their findings, published in Nature Communications, rely in part on neutron diffraction experiments at the ISIS Neutron and Muon Source high-resolution powder diffractometer (HRPD) beamline. The Queen Mary team worked with ISIS beamline scientist Dominic Fortes to examine how the crystal structure in the material changed as it was exposed to different temperatures. HRPD is one of only two facilities in the world able to conduct this type of experiment at the resolution required to detect the minuscule changes that occur.
Piezoelectric materials change shape when exposed to an electrical field or generate an electric field when put under strain. They are used in the precise motors that control mobile phone camera lenses, some batteries, ultrasound scanners, and elsewhere. Typically, these piezoelectric materials need a high-powered electric field to change shape, but that requires high voltage components and can cause the piezoelectric material to fail.
The current best available piezoelectric materials, such as PbZn0.31Nb0.61Ti0.08O3 (PZNTO(SC)), require high electric field strengths that are very close to the strength of electrical field that will cause the material to break down. PZNTO(SC) is also a single crystal composition, requiring precise control of conditions as it is grown, and careful cutting to retain the desired properties. The alternative, polycrystalline ceramics, are much easier and cheaper to fabricate, but typically do not show the same degree of shape change as monocrystalline materials, limiting their usefulness.
Previous studies had found that adding rare earth metals to ceramics like PMNPT improved their piezoelectric performance, and the Queen Mary team were interested in testing how changes in the composition and thickness of the material affected its performance.
Using the HRPD beamline alongside other techniques such as X-ray diffraction, the researchers identified one composition of PMNPT which showed high strain under a relatively low electric field at temperatures between 0 and 75oC, although the effect lessened substantially above that temperature. They also showed that thinner samples showed greater changes in shape, as surface layer effects played a more important role in the deformation.
That particular composition was particularly close to the point where the structure of the material shifted from one form, or phase, to another. Previous studies had shown that good piezoelectric materials are often found near this transition point, known as the morphotropic phase boundary. That shift, which causes the change in shape, could be induced by a relatively low electric field thanks to the sensitivity of certain nanoscale structures in the material and the relative stability of the crystal structures in the two different phases, as well as changes to other structural properties.
The results could help guide the development of new piezoelectric materials that overcome the limitations of existing systems and enable far more widespread use of these materials on a range of applications.
Read the full paper at: 10.1038/s41467-025-56920-9
