Measuring the lattice parameters of crystalline materials under an electric field at the nanoscale improves the understanding of how electronics operate. Herein, atomic-scale in situ electron microscopy is used to measure the lattice parameters near the surface of barium titanate under an electric field, which is varied to understand how it changes the lattice parameters. Applying an electric field along the a axis does not cause domain switching. Instead, as the electric field increases, so as well does the c-axis lattice parameter (c), whereas the a-axis lattice parameter (a) remains nearly constant. The c value increases as much as 4.5 − 7.0 pm at ±13.8 kV cm−1, which is beyond the measurement precision. The increases are localized near the surface and the c value recovers slowly, which suggests that the observed phenomena are related to surface effects and slow processes. These results cannot be explained by electrostrain, even when considering additional effects such as mechanical constraint, inclination of electric field, and surface and size effects. Instead, the results are explained using a combination of Joule heating, vacancy introduction, and surface effects.
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