Abstract: According to the present invention, a process is provided for producing crystalline ceric oxide particles having a particle diameter of 0.005 to 5 &mgr;m, which comprises the steps of reacting a cerium (III) salt with an alkaline substance in an (OH)/(Ce3+) molar ratio of 3 to 30 in an aqueous medium in an inert gas atmosphere to produce a suspension of cerium (III) hydroxide, and blowing oxygen or a gas containing oxygen into the suspension at a temperature of 10 to 95° C. and at an atmospheric pressure.

Abstract: A polishing composition for an aluminum disk includes water, an alumina abrasive agent and a polishing accelerator. The polishing accelerator is preferably basic aluminum nitrate. A process for polishing an aluminum disk using the polishing composition is also provided.

Abstract: According to the present invention, a process is provided for producing crystalline ceric oxide particles having a particle diameter of 0.005 to 5 .mu.m, which comprises the steps of reacting a cerium (III) salt with an alkaline substance in an (OH)/(Ce.sup.3+) molar ratio of 3 to 30 in an aqueous medium in an inert gas atmosphere to produce a suspension of cerium (III) hydroxide, and blowing oxygen or a gas containing oxygen into the suspension at a temperature of 10 to 95.degree. C. and at an atmospheric pressure.

Abstract: A stable aqueous sol of colloidal zirconia having lowered surface activity and useful for polishing semiconductors and the like, is prepared by a process comprising calcining a colloidal zirconia having a specific surface area of 10 to 400 m.sup.2 /g, a particle size of 20 to 500 nm and a dehydratable water content of 4 to 15% by weight at 400.degree. to 1,000.degree. C. to form a calcined zirconia having a dehydratable water content of 0.1 to 2% by weight, and pulverizing the calcined zirconia in the presence of a water-soluble acid or alkali in water, to form the stable sol of colloidal zirconia having a specific surface area of 5 to 200 m.sup.2 /g, a particle size of 20 to 1,500 nm and a dehydratable water content of 0.1 to 3% by weight. The stable sol of colloidal zirconia has a ZrO.sub.2 concentration of 5 to 80% by weight.

Abstract: A sintered zirconia sheet is prepared by firing a green sheet of zirconia while placing at least one weight on the sheet to apply a load thereto. Preferably a weight made of a porous material having a porosity of 5 to 30% and having a weight per unit area W (g/cm.sup.2) and a surface area S (cm.sup.2) is placed on the sheet to apply a load per unit area G (g/cm.sup.2) to the sheet under the conditions: S.ltoreq.200, G.ltoreq.5, and W/G.gtoreq.0.5. Sintered zirconia sheets free of camber, distortion or cracking are obtained, particularly when their dimensions are at least 15 cm.times.15 cm and up to 0.5 mm thick.

Abstract: A sheet-forming slurry composition is composed of zirconia powder, an organic binder, and a solvent. The zirconia powder contains 2 to 10 mol % of yttria in solid solution form and has a BET specific surface area of up to about 12 m.sup.2 /g and a mean particle size multiplied by the specific surface area of up to 3 .mu.m.m.sup.2 /g. The composition is formed into a green sheet having improved flexibility, binder removal capability, sinterability, and dimensional stability, which is then fired into a sintered part having improved denseness, gas barrier property, and surface smoothness.

Abstract: A stable basic zirconia sol can be prepared by adding to an acidic aqueous zirconia sol a dispersion stabilizer selected from the group consisting of a water-soluble organic acid having a hydroxyl group and a water-soluble organic compound having at least two hydroxyl groups, and thereafter adjusting the sol with a basic compound to pH 6 to 14.

Abstract: A process for manufacturing fine zirconium oxide powder comprises adding a hydroxide of at least one metal selected from calcium, magnesium, yttrium and a lanthanide series element to a zirconia sol, which is dehydrated, dried and calcined. A zirconia sol prepared by hydrolyzing under heating an aqueous solution containing a zirconium salt, zirconium hydroxide or zirconia hydrate and then filtering the hydrolized aqueous solution through a ultra-filtration membrane is preferably used.