Growth of Lead Fluoride Crystals from the Melt

The application of Stockbarger's technique to the growth of PbF 2 crystals is described. The melting point of PbF 2 was found to be 822°C±2°C, and owing to its fairly high vapour pressure at this temperature, the crystals were grown in an atmosphere of oxygen-free nitrogen at a pressure of 2 to 10 mm of mercury. The crystal structure was found to be of the fluorite type, and the lattice constant 5.942±0.001 Å at 18°C. Refractive indices are given for various wavelengths in the visible spectrum. The transmission limits, defined as the wavelength at which a specimen of thickness 1 cm absorbs 50% of the incident radiation, are 11.6μ and 2800 Å.