Deformation of Palladium Plates by a Small Stress during Hydrogen Absorption and Desorption

We observed an unexpected bending of a horizontally held palladium plate at 150$^{\circ}$C under a small external shearing stress. The deformation was fastest at the nominal composition of PdH$_{{\rm 0.1-0.2}}$, which is in the $\alpha+\beta$ phase. We also observed that a plate warped back and forth during a cycle of absorption and desoprtion of hydrogen when it was hung vertically, which does not have a reasonable explanation.