Zirconium oxide toughened alumina (ZTA) is a composite material of alumina and zirconia, which has excellent mechanical properties such as strength, toughness and hardness. Since ZTA exhibits both excellent strength (550-700 MPa) and high thermal conductivity (23-27W/mK), it has attracted widespread attention as a ceramic material (T-ZTA) that radiates heat from electronic devices. However, to date, it has not been disclosed in the literature how to manufacture such high-quality T-ZTA.
Generally, when the grain size of alumina in ZTA is about 1-2 μm or less, it will show high strength. However, when the grain size of T-ZTA is 2-10 μm, its bending strength (323-450 MPa) is relatively low due to the increase in grain size, and it is even inferior to commercial alumina of 370-550 MPa. In addition, when boron nitride nanotubes (BNNT) were added to T-ZTA and sintered at 1650°C, not only "21 W/mK high thermal conductivity" was found, but also "609 MPa excellent bending strength ". However, BNNT is not a cheap material.
In this study, researchers from the Korea Institute of Materials Science (KIMS) devised an interesting method to manufacture high-quality T-ZTA without using expensive additives. A high-quality T-ZTA was developed by coating the surface of alumina particles with the Y-stabilized Zirconia (YSZ) stabilized by the element Y through the grinding process. Related papers were published in Materials Science and Engineering A with the title "An easy approach to manufacture high quality zirconia-toughed alumina".
Paper link:
https://www.sciencedirect.com/science/article/abs/pii/S0921509320304093
So far, the T-ZTA manufacturing process disclosed in the literature has not specifically controlled the size of the YSZ particles. In this study, 0.25 at% Nb2O5 additive was selected because it very effectively promotes the growth and densification of the grains, suppresses the growth of the grains by YSZ on the surface of the alumina particles, and meets T-ZTA by adding Nb2O5 Densification. In addition, a liquid phase was found at the grain boundary. Due to the formation of the liquid phase, grain growth and densification occurred in the 0.25-1.50Nb 0.7YSZ Al2O3 sample sintered at 1450°C. If the sample contains a large amount of liquid phase, a large number of crystal nuclei will be used for the growth of crystal grains, and they will be difficult to grow because they will collide with each other early in the growth. At the same time, the second phase of AlNbO4 was found on the XRD pattern of 0.50-1.5Nb 0.7YSZ Al2O3, so it was used as a sintering aid for T-ZTA.
In this study, high-quality T-ZTA was prepared, which is a nanocomposite composed of Nb-doped YSZ and alumina. High-quality T-ZTA plays an important role in releasing heat in electronic components.