Crystallization of PbO·2B2O3 from Its Supercooled Melt

The growth of lead diborate and the viscosity of its melt were determined as a function of temperature. These data were used to examine several theories of the growth of crystals from the melt. The data were in good agreement with the theory of Tornbull and Cohen. At large under coolings the growth rate appeared to be controlled by the rate of diffusion across the crystal‐melt interface, whereas at smaller undercoolings the growth rate appeared to be controlled by reaction at the crystal‐melt interface.