Zirconia (ZrO,) particles are one of the most important materials for structural ceramics used at high temperatures. However, commercially available ill-defined powders prepared by milling of calcined agglomerates or by reaction of ZrCl, and O, in gas phases are normally difficult in preparation of crack-free compact for sintering or need high sintering temperatures above 1700 degrees C. On the other hand, the monosized amorphous powders of a high sinterability prepared by hydrolysis of the alkoxides are not free from the economical problem of their low productivity (< 0.2 M in final concentration).
The objectives of our first project are to develop a new method for preparation of unagglomerated ultrafine spherical particles of a narrow size distribution with the mean diameter of the order of a few ten nanometers or less in large quantities on the basis of the gel-sol technique developed in our laboratory, to elucidate the formation mechanism, and to examine the sintering properties. The “gel-sol method” essentially differs from the popular sol-gel method. The standard procedure for the preparation of ZrO, particles and their growth mechanism have already been reported in detail in the annual report of the last year (ARR 31-02).