Zirconia is an advanced ceramic material with a wide range of applications. It has very outstanding properties. Among its many properties, hardness is a very critical characteristic and has a decisive feature in applications such as dentistry and aerospace.
Below we will discuss with you the key property of zirconia’s hardness.
What is Zirconia and Why Does Hardness Matter?
The chemical formula of zirconia is ZrO₂. It is an advanced ceramic material known for its high strength, wear resistance and thermal stability. Among various performance indicators, hardness is mainly reflected in the ability to resist deformation and scratching. For zirconium oxide, high hardness makes it an indispensable material in various durable and wear-resistant applications, such as some cutting tools, crowns, prostheses and other parts.
Zirconia Hardness on Different Scales
Mohs hardness
The Mohs hardness of zirconium oxide is about 8.5, which is slightly lower than that of aluminum oxide (sapphire is 9). Its hardness is much higher than that of most metals and standard ceramics, which makes it highly resistant to scratches and surface damage in some strong wear environments and prone to corrosion.
Vickers hardness
The Vickers hardness of zirconium oxide is between 1200-1400 HV, and the Vickers hardness of different processed components may be slightly different. This value highlights its resistance to plastic deformation under concentrated load and is an ideal choice for some precision tools and wear-resistant coatings!
Knoop hardness
In some more precise applications, the Knoop hardness test can measure the hardness of zirconia to values similar to Vickers measurements, which can help verify its robustness to various testing methods.
Factors Affecting Zirconia Hardness
Crystal structure
There are three main crystal forms of zirconia: monoclinic, tetragonal and cubic. Tetragonal zirconia is usually stabilized with yttrium oxide (Y-TZP) and exhibits the highest hardness due to its dense and uniform crystal structure.
Stabilizing additives
Adding additives such as yttrium oxide (Y₂O₃) and magnesium oxide (MgO) to zirconium oxide can significantly improve the mechanical properties of zirconium oxide, including hardness. Y-TZP is called “ceramic steel” because of its excellent hardness and fracture toughness.
Processing technology
Sintering temperature, pressure and time play a critical role in determining the microstructure and hardness of zirconia. Excellent processing can ensure that zirconia products have minimum porosity and obtain more excellent hardness values.
Zirconia Hardness vs. Other Materials
Comparison With Other Ceramics
Alumina:Zirconia is slightly softer than alumina, but it has greater toughness and is superior in many applications.
Silicon carbide (SiC) and boron carbide (B₄C)：These materials are harder than zirconia, but their fracture toughness is poor, so zirconia is more popular in some environments where impact is common.
Comparison With Metal
Although not as hard as some ceramic materials, zirconium oxide is much harder than most metals, including steel and titanium. This also makes it ideal for many high-wear components.
Applications of Zirconia Based on Its Hardness
Industrial tools and wear parts
Zirconia’s high hardness and wear resistance make it an effective wear-resistant component in the automotive and aerospace industries.
Medical and dental applications
In the medical field, zirconium oxide is widely used in dental crowns, implants and surgical instruments due to its wear resistance and biocompatibility.
Jewelry and gemstones
Cubic zirconia has a luster comparable to diamond and extremely high hardness, making it a popular alternative in the jewelry industry.
FAQ
What is the hardness of zirconia?
The Mohs hardness of zirconium oxide is usually 8.5, and its Vickers hardness is between 1200-1400HV, which has very strong wear resistance and scratch resistance.
How does the hardness of cubic zirconia compare?
The Mohs hardness of cubic zirconia is also 8.5, but its main use is jewelry decoration, not industrial application.
How does zirconia compare to metals?
Zirconia is harder than most metals, such as steel and titanium, making it ideal for wear-resistant applications.
Conclusion
Zirconia’s excellent hardness makes it a leading material for industrial and decorative applications. It has very strong wear resistance and deformation resistance, and can still maintain structural integrity under extreme conditions. It is an indispensable material in many industries.