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 ( d ₃₃ ) 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.

The symmetry of single-crystal piezoelectric PbZr${}_{1-x}$Ti${}_x$O${}_3$, with $x\approx 0.31$ and $x\approx 0.46$, has been investigated by high-resolution x-ray diffraction, both at room temperature and up to and above the Curie temperature. Reciprocal space maps around a selection of Bragg reflections were collected and self-consistent patterns showing Bragg splittings were observed. The analysis of the separation of peaks from different twin domains provides precise information on PbZr${}_{1-x}$Ti${}_x$O${}_3$ symmetry when approaching the morphotropic phase boundary at $x=0.48$ from the zirconium-rich side.

Defect engineering is an effective and powerful tool to control the existing material properties and produce completely new ones, which are symmetry-forbidden in a defect-free crystal. For example, the application of a static electric field to a single crystal of SrTiO₃ forms a strained near-surface layer through the migration of oxygen vacancies out of the area beneath the positively charged electrode. While it was previously shown that this near-surface phase holds pyroelectric properties, which are symmetry-forbidden in centrosymmetric bulk SrTiO₃, this paper reports that the same phase is strongly piezoelectric. We demonstrate the piezoelectricity of this phase through stroboscopic time-resolved X-ray diffraction under alternating electric field and show that the effective piezoelectric coefficient d₃₃ ranges between 60 and 100 pC/N. The possible atomistic origins of the piezoelectric activity are discussed as a coupling between the electrostrictive effect and spontaneous polarization of this near-surface phase.