Abstract: This invention concerns a process for producing high purity silica with less than 5 ppm of impurities from cheap alkali silicate aqueous solution (water glass) for industrial use, which commonly contains more than 2000 ppm of impurities, by directly adding water glass to a mineral acid solution, such as hydrochloric acid, nitric acid, and sulfuric acid so as to dissolve impurities in the mineral acid solution and form silica precipitate, and then rinsing the silica precipitate with a mineral acid solution, provided that the viscosity of the water glass is adjusted to 10-10000 poise in advance of adding to the mineral acid solution.

Abstract: The present invention provides a manufacturing method of a conductive or superconductive thin film of mixed oxide as an easier way to apply the mixed oxide type superconductive materials to electronic devices, etc. The manufacturing method of the present invention comprises using a mixed oxide composition showing conductivity or superconductivity as a target material and sputtering it onto a substrate to form a thin film. Examples of the mixed oxide compositions showing conductivity or superconductivity and to be used as the target material in the present invention are mixed oxides consisting of lanthanoid, alkali earth metal and copper as main components, particularly, a mixed oxide consisting essentially of La-Sr-Cu-O, La-Ba-Cu-O, La-Ca-Cu-O etc. or mixtures thereof, materials containing a small quantity of other metal oxide(s), or mixed oxides mainly consisting of Yb-Ba-Cu-O, Er-Ba-Cu-O, Ho-Ba-Cu-O, Tm-Ba-Cu-O or mixtures thereof.