Experimental observation of hysteresis in a coherent metal-hydride phase transition

Abstract

We investigate the hysteresis obtained in the hydrogen absorption and desorption cycle for a single crystal [Formula: see text] superlattice. Below the critical temperature, a small but clear hysteresis is observed in the pressure-composition isotherms, while it is absent above. The experimental results thereby prove the relevance of macroscopic energy barriers for obtaining hysteresis in coherent structural transformations. The textured Pd layer exhibits substantially larger hysteresis effects, which can be related to an irreversible energy loss caused by defect generation in Pd.

Combined Light and Electron Scattering for Exploring Proximity Effects on Hydrogen Absorption in Vanadium

“…The measured temperature range for the isotherms is from 453 K to 553 K, which is above the phase transition temperatures and can avoid the crack of the samples. Each experimental data point is measured at chemical equilibrium and there is no hysteresis found, indicating that the loading and unloading are reversible [18]. The chemical potentials ∆µ versus concentration at different temperatures are obtained through the equation ∆µ = 0.5k b T ln(p/p 0 ) based on the interpolated P-C-T isotherms [5], where p 0 is a reference pressure of 1 bar.…”

Structural Phase Transitions in Niobium Hydrogen Thin Films: Mechanical Stress, Phase Equilibria and Critical Temperatures

“…Lattice expansion results in long‐ranging distortion fields of the metal lattice that cause an attractive hydrogen−hydrogen interaction and initiate the formation of a hydride phase above critical hydrogen concentrations . Hence, metal−hydrogen systems are susceptible to interface and size constraints due to the constraints’ impact on the distortion fields . This results in modified stabilities of phases .…”

“…When critical stresses are reached at phase interfaces, often stress relaxation occurs by the emergence of misfit dislocations . If, on the other hand, phase interfaces remain coherent, the nature of the phase transition is changed fundamentally . Then, thermodynamic equilibrium between phases is prevented by an elastic energy barrier that is unsurmountable by thermal fluctuations …”