Hydrogen Absorption in Pd–Ag Systems: A TPD and Electrical Resistivity Study

Hydrogen retention in Pd–Ag (silver 21 wt. %) thin foil has been tested by means of temperature-programmed desorption (TPD) in the temperature range 25–200 °C and compared to the resistivity measurements for the purpose of explaining the characteristic S-shaped resistivity curve and its minimum observed in the same temperature range. The TPD results indicated that the highest uptake of hydrogen was between 65 °C and 105 °C, with a maximum at ~85 °C. Furthermore, in all examined cases, the hydrogen desorption peak was between 140 °C and 180 °C. The resistivity measurements in argon, hydrogen, and vacuum allowed us to examine the influence of hydrogen on the resistivity of a Pd–Ag alloy. The results showed evidence of two kinds of hydrides: (1) a weak absorption at low temperature (T < 70 °C) with the hydrogen present mainly in tetrahedral sites, and (2) a strong absorption up to 150 °C with the hydrogen present mainly in octahedral sites. The behaviour of the electrical resistivity and the minimum between 90 °C and 110 °C can be explained by the two kinds of hydrogen uploaded into the metal lattice.

HIGH PRESSURE ELECTRICAL RESISTIVITY STUDY ON NONLINEAR SINGLE CRYSTAL ZINC THIOUREA CHLORIDE

Zinc thiourea chloride (ZTC) crystals were crystallized by slow evaporation technique. The lattice parameters of the grown crystals were determined by angle dispersive X-ray powder diffraction technique (XRD) and the structure was confirmed. High pressure electrical resistivity study was carried out on this crystal and the results are reported here.