水酸化物の非等温熱分解によるジルコニアナノ粉体の合成と焼結 Synthesis and Sintering of Zirconia Nano-Powder by Non-Isothermal Decomposition from Hydroxide

A non-conventional route for controlling both the particle size distribution and the morphology of yttria-stabilized tetragonal zirconia has been studied. Non-isothermal decomposition from hydroxide was chosen as a process suitable for preparing the uniformly aggregated nano-crystalline 3Y-TZP powder. The obtained powder had a particle size of 9-18 nm, and a narrow aggregate size distribution of 20-70 nm. The characteristics of zirconia non-isothermal calcination were investigated in order to choose the best heating regime. Changes in the heating schedule caused changes in the powder morphology. Calcination includes several processes: complete decomposition of hydroxides, crystallization of zirconia, close packing into aggregates, and agglomeration at elevated temperatures because of particle bridging. These processes are superimposed with elevating the calcination temperature. There are two schedules differing both in fineness of the final powder and degree of aggregation-agglomeration. A non-linear heating schedule, produced the finest powder, uniformly aggregated, and non-agglomerated. Keeping lowest possible temperature allowed preventing high-temperature bonding and bridging of particles, which results in hard agglomerates. A high packing density of 56% was achieved after slip casting and cold isostatic pressing, which allowed low-temperature sintering, resulting in a fine-grained dense ceramic body.