| 摘要 |
Improved Si3N4/ZrO2 composite ceramics are described, having low thermal conductivity and which are substantially free of surface spalling and material degradation. Such composites are produced by incorporating an additive, e.g. MgO, CaO or Y2O3, preferably Y2O3, in suitable molar proporations based on ZrO2, and sintering the mixture with Si3N4. In a preferred embodiment a powder mixture of 70% Si3N4 and 30% ZrO2, by volume, and containing 6.6 mole percent Y2O3 based on ZrO2, is formed and is sintered to produce a composite ceramic. The Y2O3 is preferably pre-reacted with the ZrO2 to form a solid solution. A sintering aid, preferably Al2O3, e.g. in an amount of about 2 to about 4%, by weight of the total mixture, can be added to permit production of the Si3N4/ZrO2 composite by pressureless sintering.
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