Zirconia – Physical and Mechanical Property Comparison of the Different Types of Zirconias

Background

The fundamental properties of zirconia ceramics which are of interest to the engineer or designer are:

·         High strength,

·         High fracture toughness,

·         High hardness,

·         Wear resistance,

·         Good frictional behaviour,

·         Non-magnetic,

·         Electrical insulation,

·         Low thermal conductivity,

·         Corrosion resistance in acids and alkalis,

·         Modulus of elasticity similar to steel,

·         Coefficient of thermal expansion similar to iron.

Types of Zirconias

There are many different types of zirconias. These have evolved as researchers and manufacturers sought to exploit the different properties of the various phases. Some of the phases are stable at high temperatures and need to be “frozen” in such that they can be used at room temperatures, while others exploit toughening mechanisms that are only found in these and few other materials. Some of these materials are listed below along with their typical abbreviations.

Table 1. The different types of zirconias.

Materials (oxides) added to stabilise or toughen the zirconia will also be noted as a prefix to the abbreviations listed in table 1. They will sometimes be used in conjunction with numbers which indicate the amount of the stabilising agent added. Typical examples include Y, Ce, Mg and A which correspond to yttria (Y₂O₃), ceria (CeO₂), magnesia (MgO) and alumina (Al₂O₃) respectively. So a material denoted as 3Y-TZP would tetragonal zirconia polycrystal with an addition of 3mol% Y₂O₃ as a stabiliser.

Property Comparison

Table 2. lists properties for various grades of zirconia and has been compiled from a variety of sources. However, as with most ceramic materials properties are dependent on many factors such as starting powders and fabrication techniques. Most ceramic fabrication techniques have been applied to zirconias such as dry pressing, isostatic pressing, injection moulding, extrusion and tape casting. Addition of impurities during processing may also introduce flaws and degrade properties.

Table 2. Typical properties of various types of zirconia.

Primary author: AZoM.com