Overview
- The Institute of Science Tokyo team reported Friday that samples of fcc FeHₓ showed a clear λ‑shaped thermal‑expansion anomaly near 1,500–1,800 K and abrupt hydrogen redistribution at about 1,600 K, signs consistent with a superionic transition.
- Researchers probed tiny iron‑hydride samples using diamond‑anvil cells, laser heating and time‑resolved X‑ray diffraction at SPring‑8, reaching pressures reported up to roughly 110–140 GPa and temperatures above 2,000 K.
- From measurements at those pressures the authors traced a phase boundary and extrapolated it to core pressures, finding the transition temperature would lie below common estimates of inner‑core temperatures but stressing that the lab did not reach true inner‑core pressures.
- Electric‑field tests produced measurable hydrogen movement in the heated lattice but diffusion rates derived from the data are extremely slow: about 0.1 micrometer in 10,000 years and far too slow to mix across the inner‑core radius on Earth’s lifetime.
- The study provides the first experimental support for a superionic iron‑hydride phase that could help explain some seismic oddities in the inner core, yet confirming any geophysical impact will require higher‑pressure experiments and tests on other iron–light‑element alloys.