PSEUDO-DENDRITIC GROWTH IN LEAD MOLYBDATE SINGLE-CRYSTAL BY CZOCHRALSKI TECHNIQUE

A pseudo-dendritic crystal growth of lead molybdate (PbMoO4) has been studied with the Czochralski technique. The observed dendritic growth is iso-directional, projecting from the circumference of the growth fr ont, where the content of impurities, melt stoichiometry and temperatu re are expected to be varied. The dendrite arm length and inter-dendri te angle are closely correlated. It is found that the grown dendrite a rms are bounded only by ten low-index crystallographic planes (001), ( 001BAR), (101), (101BAR), (101BAR), (101BAR)), (011BAR), (011BAR), (01 1BAR), and (011BAR). Based on this work, a facet transition pattern ex isting among the dendritic arms has been revealed. Further analysis fo r crystal grains in as-grown PbMoO4 single crystals indicates that a s imilar dendritic growth can also occur under conventional growth condi tions. It is further suggested that the constitutional supercooling is a major factor causing the dendritic growth in PbMoO4 single crystals .