HYDRATED ZIRCONIA DRY POWDER AND ITS PRODUCTION AND USE

PROBLEM TO BE SOLVED: To obtain hydrated zirconia dry powder capable of producing zirconia fine powder satisfiable in terms of both moldability and sinterability, and to provide a method for producing such hydrated zirconia dry powder. SOLUTION: This hydrated zirconia dry powder is such as to be 1.00-1.40 g/cm3 in true bulk density shown by the formula: A×[1-(B/100)] (A is the apparent bulk density of this dry powder (g/cm3); B is volatiles when this dry powder is calcinated at 1,000 deg.C (wt.%)). This hydrated zirconia dry powder is obtained by the following process: a hydrated zirconia sol produced by hydrolysis under heating of an aqueous zirconium salt solution is washed and concentrated through ultrafiltration, another batch of an aqueous zirconia salt solution is added to the resultant sol followed by addition of a salt, hydroxide or oxide of at least one element selected from the group consisting of Y, Ca, Mg and Ce as a sintering auxiliary in a solid state or in the form of an aqueous solution or slurry, and the resultant solution is evaporated to dryness. Zirconia fine powder is obtained by calcination of the thus obtained hydrated zirconia dry powder.