The Thermoelectric Properties of Sputtered films of Gold, Platinum, and Palladium; and of Solid Palladium containing Occluded Hydrogen
Year: 1923
Type: article
Abstract: Thermoelectric properties of sputtered films of gold, platinum and palladium.---The films were sputtered on glass in a tube containing air not specially dried, the desired shapes being secured by use of mica screens. One end of a film was kept at 0\ifmmode^\circ\else\textdegree\fi{}C; the temperature of the other junction was varied by use of an electrically heated oil bath. For monometallic couples of Au, Pt and Pd, each consisting of a film in contact with its mother metal, surprisingly large electromotive forces were observed. For the unbaked films the power line shows breaks and the values decrease with time. If the films are baked at 500\ifmmode^\circ\else\textdegree\fi{} C, however, the electromotive forces are definite though smaller and the power lines are straight, the values of $\frac{\mathrm{dE}}{d\ensuremath{\theta}}$ for the baked films with respect to the mother metal for the range 0\ifmmode^\circ\else\textdegree\fi{} to 300\ifmmode^\circ\else\textdegree\fi{} C, increasing from -.90 to -1.23 for gold, and from 6.59 to 9.6 for Pd, and being constant at 3.46 for Pt, all in microvolts per degree. These values do not vary with the thickness, and agree with the results obtained with Pt film-Au film couples.Effect of occluded hydrogen on the thermoelectric power of palladium was studied as it was thought that the peculiarities shown by the film couples might be due to occluded gas. The metal when filled with hydrogen electrolytically was found positive with respect to the gas-free metal, the value for $\frac{\mathrm{dE}}{d\ensuremath{\theta}}$ decreasing from 12 microvolts per degree at 0\ifmmode^\circ\else\textdegree\fi{} to zero at 270\ifmmode^\circ\else\textdegree\fi{} C. When filled by cooling in hydrogen in a furnace, smaller values were obtained. Baking removed the effect. Electron theory in its simplest form, taking the thermoelectric power as proportional to the logarithm of the electronic pressure ratio, is shown to give a value for the gas-filled metal due to the effect of hydrogen in increasing the electronic pressure, which agrees approximately with the experimental value.
Source: Physical Review
Author: R. M. Holmes
Institution: Cornell University
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1982495682