Effect of a Small Amount of Nb2O5 Addition on the Phase Stability and Mechanical Properties of Yttria-Stabilized Zirconia Composite
Date Issued
2014
Date
2014
Author(s)
Lian, Tseng-Wen
Abstract
The 3 mol% Y2O3-stabilized zirconia (3YSZ) exhibits excellent mechanical properties such as high strength and high fracture toughness. Recently, 3YSZ/20wt%Al2O3 powder has also been widely used for its excellent strength and thermal stability. In the present study, a small amount (0-2 mol%) of niobium oxide (Nb2O5) was added into 3YSZ and 3YSZ/20wt%Al2O3 systems. The specimens were sintered at 1600°C in air for 1 hour. The effect of Nb2O5 addition on the phase stability, microstructure, mechanical properties and thermal conductivity was then investigated.
The results indicate that the fracture toughness is increased significantly after the addition of 0.5 mol % Nb2O5 both in the 3YSZ and in 3YSZ/20wt%Al2O3 systems. The tetragonal ZrO2 phase in the composites becomes unstable as the Nb2O5 content is high. The instability of tetragonal ZrO2 promotes its transformability, it results in the phase transformation from tetragonal phase to monoclinic phase. The toughening mechanism induces the increase of fracture toughness in the zirconia systems. Other mechanical properties such as strength and hardness remain the same after the addition of a small amount of Nb2O5.
The 3YSZ/20wt%Al2O3/Nb2O5 specimens exhibit higher flexural strength and higher fracture toughness comparing to those of the 3YSZ/Nb2O5 specimens. The increase of flexural strength and fracture toughness may be related to the presence of residual stress in the ZrO2-Al2O3 systems.
Subjects
氧化鈮
氧化釔安定氧化鋯
正方相氧化鋯
韌化機制
破壞韌性
強度
硬度
Type
thesis
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