| Abstrakt: |
An investigation was carried out of the sintering of zirconia containing 4-15 mole % yttrium oxide in which it was confirmed that the sintering of the materials begins at 500°C. It was established that the over the range 1200-1500°C the sintering kinetics of ZrO is proportional to τ only when the proportion of added yttrium oxide does not exceed 8 mole %, i.e., when a relative small amount (30% or less) of the new phase (cubic ZrO) is formed and the compaction depends on selfdiffusion. A higher YO content causes heterodiffusion to become dominant and sintering to be inhibited. The shrinkage proceeds according to the law Δ ℓ/ℓ ∼ τ in this case. The sintering process is affected adversely by an increase in the YO content. The rapid growth of the crystals at temperatures above 1500°C and the high open porosity of the material causes the porosity of the grains to increase so that it is then not practicable to produce a highdensity sintered material by combining sintering and stabilizing, more especially with a high YO content, viz., 6-15 mole %. The degree of sintering decreases with an increase in the purity of the material in which case a highdensity sintered material can be produced either by fusing the ZrO with the yttrium oxide, or by hotpressing, or by separating the stabilizing and sintering processes and fine-grinding the material prior to the second firing operation. [ABSTRACT FROM AUTHOR] |
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