Crystal Growth and Thermal Etching of Argon

Thermal etching and grain size of argon polycrystals grown from the melt and the vapor near the triple-point temperature and below have been investigated. Average grain area and its observed dependence on canonical crystal growth parameters such as: temperature gradient, supersaturation, chamber geometry, coolant temperature, initial nucleation conditions, and especially growth rate, is described and compared with the same problems in high-temperature crystal growth. For a growth rate of 1.0 cm/h average grain area was about 0.1 cm2 with the largest grain observed measuring 1.0×1.0×0.7 cm. The grain area decreased with increasing growth rate, asymptotically approaching zero. Surface ``rosettes'' and a method for crystal orientation, depending on occurrence of slip lines on the crystal surfaces, are described.