鉛を含まない新しい圧電体材料を開発(Scientists create new lead-free piezoelectric materials)

Piezoelectric materials usually rely on their crystal structure alone to create electrical charge in response to strain. This makes the materials attractive for a variety of sensing applications. Park et al. present a different strategy by introducing gadolinium into non-piezoelectric cerium dioxide (see the Perspective by Li). This approach also creates oxygen vacancies that turn the material into one with a frequency-dependent piezoelectric effect under a static electric field. The size of the effect is similar to that of commercial piezoelectric materials, and the strategy should work more generally for a wide class of materials. —BG

Piezoelectrics are materials that linearly deform in response to an applied electric field. As a fundamental prerequisite, piezoelectric materials must have a noncentrosymmetric crystal structure. For more than a century, this has remained a major obstacle for finding piezoelectric materials. We circumvented this limitation by breaking the crystallographic symmetry and inducing large and sustainable piezoelectric effects in centrosymmetric materials by the electric field–induced rearrangement of oxygen vacancies. Our results show the generation of extraordinarily large piezoelectric responses [with piezoelectric strain coefficients (d₃₃) of ~200,000 picometers per volt at millihertz frequencies] in cubic fluorite gadolinium-doped CeO_2−x films, which are two orders of magnitude larger than the responses observed in the presently best-known lead-based piezoelectric relaxor–ferroelectric oxide at kilohertz frequencies. These findings provide opportunities to design piezoelectric materials from environmentally friendly centrosymmetric ones.