Resistivity maximums due to growth of hydrogen-ordered domains in resistivity curves of Pd–H alloys during heating up with constant rates

Hydrogen migration in fast cooled Pd–H alloys around 50K

“…The direction of the change in height of the resistivity maximum upon heating rate is opposite, in some times, to that expected for heating curves after slow cooling (0.098 K/min) if the resistivity increases with hydrogen ordering and decreases with disordering. In fact, the resistivity increase due to the ordering and the decrease due to the disordering are limited only to the early stage of the ordering as mentioned before [9,14,[16][17][18]. At the later stage of ordering, the resistivity decreases passing through the maximum as shown in the isothermal annealing curves for long time annealing [14].…”

“…The resistivity increase in the early stage and the decrease in the disordering are caused by the nucleation and growth of ordered domains and by the shrinking (when the size of the domains is smaller than the critical size) and/or disappearance of the domains, respectively. The resistivity also decreases in the later stage of hydrogen ordering due to the growth of the ordered domains [9,14,17]. The resistivity changes by fast cooling of the specimens were fairly large comparing with the change by slow cooling.…”

“…The causes of these complex behavior of the resistivity curves has been discussed in the previous papers [9,18] for the heating curves after cooling with various rates. The two peaks correspond to growth of the ordered domains and to shrink of the ordered domains, respectively.…”

“…It has been already clarified by extensive studies with electrical resistivity measurement and neutron scattering measurement that the resistivity of Pd-H(D) alloys increases in the early stage of hydrogen ordering and decreases due to the disordering [2,5,[9][10][11][12][13][14][15][16][17]. The resistivity increase in the early stage and the decrease in the disordering are caused by the nucleation and growth of ordered domains and by the shrinking (when the size of the domains is smaller than the critical size) and/or disappearance of the domains, respectively.…”

“…The Pd-H alloy specimens used in the present experiment were the same ones as used in a previous paper [9] and were prepared from the material supplied by Tanaka Kikinzoku Kogyo Corporation. The thickness of the Pd foils was from 50 to 100 m. Before fast cooling of the specimens, the specimens (PdH 0.49 , PdH 0.52 , PdH 0.55 , PdH 0.58 and PdH 0.59 ) were held for 5 min or more around 80 K and then were fast cooled to below 20 K with a constant rate, 9.9 K/min, to obtain the structurally disordered state of hydrogen.…”