High-purity quartz glass and method for the preparation thereof

Abstract

Provided are high-purity quartz glass having a high purity, in particular, with little zirconium (Zr) and manufactured at low costs from natural quartz as the starting material and a method for the preparation thereof. High-purity quartz glass is manufactured, in a method for the preparation of natural quartz glass which is prepared by subjecting crystalline natural quartz to fusion by heating, in conducting refining of the starting material of the crystalline natural quartz by successively practicing a combination of at least one unit refining procedure, in a procedure in which a portion of the starting quartz after practicing the specified unit refining procedure is taken by sampling for analysis, the same is decomposed with hydrofluoric acid or an acid mixture of hydrofluoric acid and another inorganic acid, the decomposition solution is subjected to evaporation to dryness either as such or after addition of another inorganic acid, the residue is melted by heating with admixture of a salt or hydroxide of an alkali metal, the salt or hydroxide of the alkali metal is then dissolved in an aqueous solution of an inorganic acid or in pure water, the solution is subjected to quantitative analysis for the impurities therein to determine the contents of impurities in the crystalline natural quartz and the refined crystalline natural quartz, of which the content of impurities has been found to be lower than a specified value, is subjected to fusion by heating as a starting material to prepare high-purity quartz glass.