The crystals were prepared by the Czochralski method, drawing each in the form of a wire through a 2 mm hole in a mica disk which floated on the surface of the zinc, kept just a few degrees above its melting point. After slight amalgamation, the crystals split readily along the basal plane, normal to the vertical axis. The angle between this axis and the axis of the wire is the orientation $\theta$ of the crystal. Each end of a crystal was sealed with cadmium into a copper block, one of which was kept at 0° C, the other at a temperature $T$, varied up to 290°C. The ratio of thermo-e.m.f. $E$ to $T$ is found not to be a linear function of $T$ but to increase with $T$ more rapidly. The curves for the higher values of $\theta$ lie above those for lower values, so that with a circuit of differently oriented crystals the e.m.f. is directed, at the hot junction, from the crystal of higher to that of lower orientation. For wires with $\theta =14\mathrm{}°$ and $\theta =86.5\mathrm{}°$, the e.m.f. with $T=250\mathrm{}°$ would be 6.50×${10}^{-4\mathrm{}}$ volt. The neutral temperature $(\frac{\mathrm{dE}}{\mathrm{dT}}=0)$ decreases from about 500° for $\theta =14\mathrm{}° \mathrm{to} 40°$ for $\theta =86.5\mathrm{}°$.

Close

PrevNext

View figure in article