A thin film of perovskite slowly changes its crystal structure. Atoms rearrange like passengers in a crowded train car gradually finding more comfortable spots. This process took several hours, and throughout, researchers tracked it with X-rays.
It turned out that the rearrangement proceeds at two different rates. Some regions, domains, grow at a constant speed: their boundaries move at about 2 nanometers per hour. It's like a checkout line advancing steadily. But there's another, slower process: some domains first 'get stuck,' then start to speed up. Over time, their dynamics follow a power law — the longer the process, the faster it becomes.
Such unevenness matters for devices that use phase transitions to store information. If domains keep moving hours after the transition begins, the material's electrical properties can change unpredictably. Understanding this dynamics will help create more stable devices.
The domain boundary speed in this experiment was 2 nanometers per hour. For comparison, a human fingernail grows about 1000 times faster.