What's the difference between alumina and zirconia?

So far,  the application of ceramic has developed rapidly in all industries. Technical ceramics have been widely used in many fields in recent years with their superior characteristics. Among them, zirconia ceramics and alumina ceramics are the most common of all industries applications.  But there is some outstanding difference in characteristics of the two types of ceramics, which one is more suitable to them in their specific needs?  We'd like to take both materials for making a brief comparison as below:

1. Density

The density of zirconia ceramics is twice that of alumina ceramics. In contrast, zirconia ceramics have better compression resistance. The density of alumina ceramics over 95% purity is 3.65g/cm³, and the density of yttria partial stabilized zirconia ceramics is 6g/cm³.

2.Surface quality

Zirconia ceramic is easier to obtain a mirror-like, extremely smooth surface, and has less friction, which can further improve the life of the ceramic parts, greatly reduce the replacement and maintenance in the devices.

3.Fracture toughness

The toughness of zirconia ceramics is 4 times that of alumina ceramics. Even if zirconia is freely dropped from a height of one meter, there will be a few chippings.

4. Coefficient of friction: 

The friction coefficient of zirconia ceramics is only 1/2 of that of alumina ceramics, while the friction coefficient of alumina ceramics itself is very low. In actual use, it is more necessary to consider both elastic modulus and hard modulus. The specific material that can be worn depends on the actual use.

5.Chemical stability

High purity alumina over 99.5% has better corrosion resistance, it could withstand HF, aqua regia.

6.Cost comparison

High purity alumina is more cost-effective material than zirconia, especially for high volume or large-size ceramic parts.

Zirconia ceramic structural part is a very important structural ceramic newly developed next to alumina ceramics. Due to some of its good properties (such as its fracture toughness higher than alumina ceramics), zirconia ceramic structural parts have received increasing attention.