Effect of Particle Geometry and Nb2O5 Addition in the Sintering of Partially Stabilized Zirconia with Y2O3

Abstract

Zirconia (ZrO 2 )has several applications in diverse industrial segments due to its excellent properties, especially regarding resistance to mechanical stress and high-temperature scenarios. However, due to phase transformations that this ceramic material exhibits at various temperatures, the appearance of cracks in the sintered compact during cooling is perceived. Studies have been performed in the way to stabilize zirconia during the sintering process by adding small quantities of other oxides, such as Y 2 O 3 , CeO, MgO and Nb 2 O 5 . Some studies show that the use of Nb 2 O 5 in the system ZrO 2 -Y 2 O 3 promotes an increase in its fracture toughness. Additionally, there are several controversies about the effect of the content and the polymorph of Nb 2 O 5 on zirconia stabilization. There are several commercial zirconia powders partially stabilized in the form of granules obtained by the spray dryer method which promotes better densification of the green and sintered compacts. This study aims at evaluating the effect of adding 0.8 % and 2.0 % (by weight) of monoclinic Nb 2 O 5 in 3Y-TZ-E (Tosoh) on the stabilization of this zirconia and the grinding effect of 3Y-TZ-E granules on the densification and on the sintered compact microstructure. Sintered compacts were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The results indicate that the use of 2.0 % (in weight) of Nb 2 O 5 implies in the destabilization of tetragonal zirconia and in the formation of Zr 6 Nb 2 O 17 . No significant difference was observed in the densification and in the grain size of the unground TZ-3Y-E with the addition of 0.8 % (in weight) of monoclinic Nb 2 O 5 .