EFFECT OF THE DIFFERENT SINTERING ATMOSPHERES ON THE STRUCTURAL CHARACTERISTICS OF THE PARTIALLY STABILIZED ZIRCONIA DOPED WITH 8wt%Y₂O₃

Resumo

Thermo-mechanical and electrical properties of zirconia-based ceramics have led to a wide range of advanced and engineering applications like solid electrolyte in oxygen sensors, fuel cells and its low thermal conductivity has allowed its use for thermal barrier coatings for aerospace engine components. In this study, the effect of the sintering at-mosphere in the in-situ stabilization of the Cubic- and Tetragonal-ZrO₂ phases were studied in ZrO₂-8wt.%Y₂O₃ ceramics. Powder mixture was compacted by cold isostatic pressing and sintered at 1600^oC-30 minutes, in air and under vacuum. Sintered samples were characterized by relative density, X-ray diffraction and Scanning Electron Microscopy. Ceramics with relative density near to 90% were obtained in both sintering atmospheres and the sintering in air demonstrate an increasing of the cubic+tetragonal-ZrO₂ stabilization, reducing the martensitic (T-M) trans-formation after sintering. In this form, a lower monoclinic is formed and consequently, a few higher densification was obtained in samples sintered in air. The lattice parameters of the tetragonal and cubic phases were determined to be similar and its proportion (65% and 35% respectively for ZrO₂-8wt.%Y₂O₃) is no influenced by the sintering atmosphere.