A method consisting of a moving temperature gradient for producing centimeter-long crystals in commercial tantalum wire is described. Based on one run, the method was less successful on commercial molybdenum wire. Thermionic projection tube patterns from the resulting crystals were qualitatively the same as that from tungsten. Plateau-like structure similar to that of tungsten was observed on both the tantalum and molybdenum crystals.

• Received 9 November 1953

DOI:https://doi.org/10.1103/PhysRev.94.309