Optical glass and its production

Claim 1

Method of producing an essentially bubble-free glass boule, suitable for use as a low loss optical waveguide material, and of good composition control in mixed oxide glass systems which include relatively volatile minor constituents, comprising 1. introducing a quantity of homogeneous prereacted particulate matter into a gas stream, said matter being of such particle size as to pass through a 20 mesh screen but not through a 100 mesh screen 2. directing the gas-particle stream into a plasma discharge against a bait, thereby fusing the particulate matter to form said glass boule wherein the particulate matter has been produced by a. producing an intimate mixture of glass forming materials, which materials comprise at least 50 mole percent of a major constituent and at least 5 mole percent and less than about 40 mole percent of at least one minor constituent, at least one of which minor constituents, when in oxide form, possesses a vapor pressure at least 1.5 times as great as the vapor pressure of the major constituent, when in oxide form, at the temperature necessary to fuse the particulate matter to form the glass body; b. producing a particulate precursor material from the intimate mixture; c. heat treating the particular precursor material to produce an at least partially glassy product, and d. screening the heat treated material and selecting a cut of powder passing through a 20 mesh screen but not passing through a 100 mesh screen.