X-Ray Studies of Bismuth Single Crystals

A new photographic method of measuring integrated intensities of x-rays reflected by crystals has been developed. The plate is calibrated with the same wavelength of rays as those measured. The exposures are adjusted so that each measurement produces about the same blackening of the plate. The resultant lines are measured by means of a microphotometer. A new type of x-ray ionization spectrometer has been designed and was used for the present research problem. The ionization chamber is fixed and the ionization current is measured by means of a Hoffman electrometer, which makes it possible to measure x-ray intensities down to the lower limit imposed by cosmic rays and radio-active effects. By means of a precision adjustment the angle of the crystal can be adjusted to ten seconds of arc. The lattice constant for the (111) plane of a bismuth crystal has been measured by the Siegbahn method and was found to be D = 3.94531Å ∓ .00003Å at 23° Centigrade. The previous value was given by James(1) was D = 3.95Å ∓ 0.08Å. The lattice constant for the (111) plane of a bismuth crystal was found to be D = 3.73 Å ∓ 0.01 Å. The parameter of the bismuth lattice was measured and was found to be 0.351Å ∓ .001Å. The previous value given by James(1) was 0.307Å ∓ .065Å. No difference was found between the 1attices of bismuth crystals grown in a magnetic field and nonmagnetic bismuth crystals. The lattice constants of the (111) planes are alike to within 0.0005%. The anomalous changes of density of bismuth single crystals grown in a magnetic field reported by Goetz and Focke(5) and the anomalous thermoelectric effects of these crystals reported by Goetz and Hassler(3) must be ascribed to changes in the secondary lattice structure.