Nature Materials, Published online: 26 February 2025; doi:10.1038/s41563-024-02092-8The authors demonstrate a chemopiezoelectric effect in which the displacive migration of oxygen vacancies driven by an electric field induces a large strain in the surface layer of thin (K,Na)NbO3 ceramics. They achieve an electrostrain of 1.9% under a field of −3 kV mm−1, with thermal stability up to 200 °C.