| abstract |
The resistance-heated boat of the present invention is comprised of a heating portion and a crucible portion separated by a heat conducting, substantially non-electrical conducting portion. n The heating portion is fabricated of an electrically conductive material capable of being resistance heated to high temperatures. Mixtures of titanium diboride with boron nitride, aluminum nitride or silicon carbide typically provide electrical conductivity in the desired range. Zirconium diboride, mixtures of boron nitride, silicon nitride, aluminum nitride or titanium diboride, or mixtures thereof are also useful. n The crucible portion of the boat provides a vaporization surface and is fabricated of materials selected for their ability to provide wettability by the metal to be vaporized, a desired chemical and physical resistance to the metal, or impurities in the metal, to be vaporized and to the vaporization atmosphere. Titanium diboride, zirconium diboride and mixtures thereof are eminently useful in providing a vaporization surface. n The separating portion is formed of a heat-conducting, substantially non-electrical-conducting material. The separating portion may also be comprised entirely, or mixtures of, materials containing a major portion, of boron nitride, boron oxide, or mixtures thereof. A preferred material is boron nitride. |