High-dispersion sol or gel of monoclinic zirconia supermicrocrystals and production of the same

A process for producing a high-dispersion product which is a sol or gel of monoclinic zirconia microcrystals which comprises:

• adding water to hydrated salt crystal composed mainly of zirconyl chloride in an amount of 400 ml or less per 1 gram atom of zirconium so as to produce a mixture;
• subjecting said mixture to hydrothermal treatment in a sealed container at more than 130.degree. C. for more than 24 hours to produce a white pasty product;
• diluting said white pasty product with water so that the zirconium concentration decreases below 1 mol/liter to produce a diluted product;
• adjusting the pH of said diluted product to 3 to 7;
• and
• concentrating said diluted product to obtain a high-dispersion product which comprises a sol or gel of isolated monoclinic zirconia microcrystals dispersed in an aqueous solution without agglomeration at a concentration of 0.1 to 1 mol/liter, wherein said monoclinic zirconia microcrystals have uniform size, and a diameter or width smaller than 100 angstroms, and wherein said sol or gel is translucent.

A process for producing a high-dispersion product which is a sol or gel of monoclinic zirconia microcrystals which comprises:

• subjecting to hydrothermal treatment in a sealed container an aqueous solution which contains more than 1.5 mol/liter of zirconium salt or hydroxide based on zirconium concentration and having such a composition as to produce more than 3 mol/liter of hydrochloric acid after hydrolysis, said hydrothermal treatment being conducted at more than 130.degree. C. for more than 24 hours so as to produce a white pasty product;
• diluting said white pasty product with water so that the zirconium concentration decreases below 1 mol/liter to produce a diluted product;
• adjusting the pH of said diluted product to 3 to 7;
• and
• concentrating said diluted product to obtain a high dispersion product which comprises a sol or gel of isolated monoclinic zirconia microcrystals dispersed in an aqueous solution without agglomeration at a concentration of 0.1 to 1 mol/liter, wherein said monoclinic zirconia microcrystals have uniform size, and a diameter or width smaller than 100 angstroms, and wherein said sol or gel is translucent.