Agglomerate and Particle Size Effects on Sintering Yttria‐Stabilized Zirconia

Abstract

Agglomerate and Particle Size Effects on Sintering Yttria-Stabilized Zirconia 1950 vol% hexagonal phase is formed during sintering, a percentage adequate for retarding grain growth yet not so high that the reversion causes porosity or other problems. Sintering at higher or lower temperatures requires adjusting of the La,O, composition to obtain the proper concentration of hexagonal phases. Sintering at other temperatures was not as successful in the present study but appears to be possible in principle. The La,O,-Y,O, materials fabricated by this process are near enough to theoretical density to have excellent optical transmittance properties. Using the controlled transient second solid phase sintering mechanism requires a particular set of phase relations that result in a high-temperature two-phase field and a lower-temperature singlephase field for the same composition. Further, these fields must be at ~0 . 8 of the melting point for sufficiently rapid diffusion kinetics. Such phase relations occur for several rare earth-oxide combinations, suggesting that many other systems can be sintered by this mechanism. Other systems have been examined and the results will be reported elsewhere.

Factors influencing particle agglomeration during solid-state sintering

“…Martin et al [25] used 10 13 for β in their simulations. In the present paper, we choose β = 10 12 and Δt = 1 s. Actually, we also checked simulations with β = 10 13 and Δt = 1 s or β = 10 12 and Δt = 0.5 s, the same results can be achieved as those presented in the following sections.…”

“…Agglomeration has shown significant influences on sintering process and compaction in experiments [12,13] and simulations [14][15][16][17]. Ciftcioglu et al [18] investigated the effect of agglomerate strength on sintered density experimentally and achieved a conclusion that the sintered density of yttria powders decreased with increasing agglomerate strength.…”

“…Ciftcioglu et al [18] investigated the effect of agglomerate strength on sintered density experimentally and achieved a conclusion that the sintered density of yttria powders decreased with increasing agglomerate strength. Rhodes [12] found that agglomerates limited attainable green density, interfered with the development of microstructure, impeded initial-stage sintering kinetics, and limited the potential benefit of fine crystallites in final-stage sintering. Lange et al [13] found that dry powder routes to powder consolidation could produce large agglomerates, which resulted in large crack-like voids due to differential sintering.…”

The Role of Powder Packing in Sintering

“…The strong dependence of p on Go will require that the packing perfection be improved rapidly with decreasing grainsize, or the benefits derivable from the use of small grains cannot be realized. This is in agreement with the observations of Rhodes (8). One may expect, in fact, that at some low grain size the required packing perfection may not be practically achievable in ceramic bodies of a useful size.…”

Colloidal Processing of Ceramics

“…The pioneering work of ceramists, 2,[7][8][9][10] who first demonstrated the important relations between structure, properties, and processing of ceramics; of researchers, [11][12][13][14] who developed novel synthetic pathways for producing ceramic powders with controlled purity, morphology, and size; and of colloid scientists, who developed the theoretical framework for modeling colloidal interactions in suspension [15][16][17][18][19][20] as well as techniques for directly measuring such forces, [21][22][23][24] have provided the scientific foundations of this field. Indeed, it is the interplay between these groups of researchers and the collective body of knowledge generated that has led to the significant advances outlined in the remainder of this review.…”