Crystal Growth in the System PbO-B2O3

The temperature dependence of the rate of growth of PbO/2B2O3 from lead borate melts with PbO/B2O3 mole ratios of 1/3,1/2, 2/3, and 1 was determined. The maximum growth rates occurred from those melts which contained a slight excess of PbO. The results are explained on the basis of a modification in the structure of the melt in the interfacial zone as the PbO content is changed. Such changes markedly affect the fluidity of the melt, alter the concentration of crystallizable species, and may reduce the driving force for crystallization.