PURPOSE: To obtain a glass spherical powder suitable for producing a glass thin film or the like by giving a specific glass composition and controlling glass transition point, softening point and average particle diameter within the specific range.
CONSTITUTION: The glass spherical powder having 550-750°C glass transition point, 700-950°C softening point, 0.1-5μm average particle diameter and substantially no pores is obtained by weight barium nitrate, boric acid, silica sol and alumina sol so as to have a glass composition contg. 40-70wt.% SiO2, 5-23wt.% Al2O3, 2-18wt.% B2O3 and 10-30wt.% RO (R is one or more kind of Mg, Ca and Ba), charging them to a vessel, dissolving or diluting and dispersing them in a purified water, feeding the obtained mixure solution or sol having 5wt.% solid concn. expressed in terms of oxide to a spray thermal decomposition device shown in a figure by a constant delivery pump, spraying it together with simultaneously supplied compressed air from a binary fluid spray nozzle into a flame atmosphere having 800-1800°C furnace temp. at its upper part as fine drops of max. 100Mm size to heat-decomposing, quenching and collecting the result in a bag filter.
ISHIKAWA MASAAKI
SUYAMA YOSHIE
