A chemical vapor-deposition technique was developed for epitaxial growth of a-Al203 single crystals utilizing the reaction :Stephens and W. J. Alford, "Dislocation Structures in Single-Crystal AlzO:,," J . Am. Ceram. Soc., 47 [2] 81-86 (1964).Robert Schcuplein and Peter Gibbs, "Surface Structure in Corundum: I," ibid., 43 [9] 458-72 (1960).ANL-5750, 70 pp. (1957).

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A "double-clamshell" arc image furnace system has been successfully utilized in a practical arrangement for the measurement of thermal expansion and electrical conductivity under a controlled atmosphere. Maximum sample temperature of 2138°K has been achieved by using two 5000 W xenon arc lamps as energy sources. At 1500 o K, a temperature gradient of 6°K/cm was measured along the furnace axis by thermocouples shielded with alumina, but without a sample in position. The thermal conductivity of a sample would reduce the gradient to less than 1 0 K/em.