Hysteresis behaviour of electrical resistance of the Pd - H system measured by a gas-phase method

Abstract

The hysteresis behaviour of electrical resistance during the absorption - desorption processes in the -, - and -phase regions of the Pd - H system, respectively, have been investigated at 323 K by a gas-phase method. A small extent of hysteresis in relative electrical resistance over the cyclic absorption - desorption processes in the single-phase region has been observed, showing slightly larger -values for desorption processes than for absorption processes, where is the initial resistance of a hydrogen-free sample. In cyclic desorption - absorption scans commencing from the absorption branch of p - c isotherms in the two-phase plateau region, similar hysteresis loops to those of p - c isotherms have been observed for plots of versus [H]/[Pd]. On the other hand, for cyclic desorption - absorption scans starting from absorption pressures, corresponding to hydrogen concentrations near the -phase boundary composition, -values do not return to those of desorption plateau in the two-phase region. Values of relative resistance over subsequent desorptions from absorption pressures with MPa decrease gradually with decreasing H content down to -phase boundary compositions and exhibit almost the same values as those observed for the absorption processes and, on entering the two-phase region, the -values remain almost constant with decreasing [H]/[Pd], i.e. at at 323 K. The large hysteresis of resistance relationships can be attributed to creations of lattice strains accompanied by dislocation formation arising from -phase hydride transitions and by further highly dissolved hydrogen in the -phase region.

Low Concentration Response Hydrogen Sensors Based on Wheatstone Bridge

“…In order to compare the two sensors under same interval test time, the unannealed sensor at 200 ppm did not reach a stable maximum response. These results indicate that with increasing hydrogen concentration, the diffusion rate of hydrogen and the rate of hydride formation increased [2,3,4,15]. Compared with unannealed sample, the output response of the annealed sensor was somewhat reduced, however, its zero drift and repeatability were greatly improved.…”

Occurrence of hysteresis-like behavior of resistance of film in the dynamical measurement of heating–cooling cycle

“…Such hysteresis have been observed in Bi films even without structural changes [4]. A hysteresis behavior was also observed in Pd film which was ascribed to absorption and desorption of hydrogen during heating-cooling cycle [5]. Therefore, it motivated us to investigate more thoroughly the temperature dependence of electrical resistance in heating-cooling cycles for Sb 2 Te 3 film in vacuum.…”

Low Concentration Response Hydrogen Sensors Based on Wheatstone Bridge

“…Among those sensors, work function based sensors typically need to work at elevated temperature in order to maintain high sensitivity [2,3]. While resistance based sensors are extensively applied due to ambient working temperature and convenience for measurement [2,4,5,6].…”