Last Updated on March 29, 2023 by You Ling
Zirconia ceramic is a very strong ceramic material. It has very high strength. toughness and corrosion resistance. The application is very extensive.
Many people want to know more about zirconia ceramics. So we wrote this article to help you all.
- What is Zirconia Ceramic
- The History of Zirconia Ceramic
- Characteristics of Zirconia Ceramic
- Classification of zirconia ceramics
- Preparation process of alumina ceramics
- How to choose the appropriate zirconia products:
- How to choose the appropriate zirconia ceramic manufacturer:
- Application fields of zirconia ceramics
- Development trends of zirconia ceramics
1、What is Zirconia Ceramic?
Zirconia ceramic is a white ceramic material that appears yellow or gray when it contains impurities, typically including HfO2, which is difficult to separate. Zirconia ceramic is an extremely durable ceramic material that possesses excellent hardness, fracture toughness, and corrosion resistance. It has high strength, toughness, wear resistance, and corrosion resistance, making it suitable for use in operating environments where plastics, metals, and other ceramic materials cannot withstand.
2、The History of Zirconia Ceramic
Zirconia was first discovered in 1892 and was thought to only exist naturally as the monoclinic crystal “baddeleyite.” Due to its limited availability, baddeleyite was not widely used. Additionally, zirconia has a high melting point of 2,750°C, making it difficult to form single crystals through dissolution. In 1930, “stabilized zirconia,” which was a polycrystalline ceramic, was invented by adding stabilizers. Stabilized zirconia was mainly used as a refractory material and could withstand high temperatures of up to 2,540°C and chemicals. In 1937, German mineralogists M.V. Stackelberg and K. Chudoba first discovered microcrystalline cubic zirconia in metamictized baddeleyite.
In the 1960s, French scientists Y. Roulin and R. Collongues began to study the cultivation of single-crystal cubic zirconia. They used the “cold crucible” method, which involved placing molten zirconia in a crucible with a solid zirconia surface to allow it to crystallize. However, this method could only produce small single crystals. Soviet scientist V.V. Osiko later improved this technology at the Lebedev Physical Institute in Moscow. His invention was called the “cold crucible” method, and the artificial gemstones produced by this method were known as “Fianit” in the Soviet Union. This invention was first disclosed in 1973 and began commercial production in 1976. By 1980, the annual production of cubic zirconia produced by this method exceeded 50 million carats (10,000 kg).
3、Characteristics of Zirconia Ceramic
Zirconia ceramic has high melting and boiling points, high hardness, insulation at room temperature, and conductivity at high temperatures, among other excellent properties.
High density – up to 6.1 g/cm^3
High flexural strength and hardness
Excellent fracture toughness – impact resistance
High maximum use temperature
Good frictional properties
Low thermal conductivity – approximately 10% that of alumina
Resistant to acid and alkali corrosion
Elastic modulus similar to steel
Thermal expansion coefficient similar to iron
4、Classification of zirconia ceramics
Zirconia is usually purified from zirconium ores. Under normal pressure, pure ZrO2 has three crystal structures: Monoclinic zirconia (m-ZrO2), Tetragonal zirconia (t-ZrO2), and Cubic zirconia (c-ZrO2). These three crystal forms exist in different temperature ranges and can transform into each other:
Monoclinic zirconia (m-ZrO2) <950℃ 5.65g/cc
Tetragonal zirconia (t-ZrO2) 1200-2370℃ 6.10g/cc
Cubic zirconia (c-ZrO2) >2370℃ 6.27g/cc
These three crystal structures have different physical and chemical properties. To obtain the required crystal form and performance in practical applications, different types of stabilizers are usually added to make different types of zirconia ceramics:
Magnesia-stabilized zirconia (MSZ) – stabilized by magnesia, used for high-temperature applications, not easy to undergo phase transformation at high temperatures, has a heterogeneous microstructure that prevents grain boundary sliding, toughened by transformation, and has high fracture toughness.
Yttria-stabilized zirconia (YTZP) – stabilized by yttria, with a microstructure mainly composed of the tetragonal phase, has extremely high strength and toughness, used at temperatures below 500°C, toughened by transformation to resist crack propagation, excellent chemical resistance, and excellent wear resistance.
Ceria-stabilized zirconia (CSZ) – stabilized by ceria for high-temperature and high or low pH environments, toughened by transformation, maintains strength under steam and pressure conditions, and has ceria oxide filling crystal structure vacancies to prevent low-temperature degradation.
Zirconia Toughened Alumina (ZTA) – zirconia toughened alumina, provides 20-30% higher strength than alumina at lower cost than stabilized zirconia, toughened by transformation, has higher toughness, hardness, and wear resistance than alumina.
5、Preparation process of alumina ceramics
The production of zirconia ceramics requires the preparation of high-purity, well-dispersed, ultra-fine, and narrow particle size distribution powders. There are many methods for preparing ultra-fine zirconia powder, and the purification of zirconia mainly includes chlorination and thermal decomposition, alkali metal oxide decomposition, lime melting, plasma arc, precipitation, sol-gel, hydrolysis, spray pyrolysis, etc. Powder processing methods include co-precipitation, sol-gel method, evaporation method, supercritical synthesis method, microemulsion method, hydrothermal synthesis method, and gas-phase deposition method, etc.
The forming methods of zirconia ceramics include dry pressing, isostatic pressing, slip casting, hot pressing casting, tape casting, injection molding, plastic extrusion molding, and gel casting. Among them, injection molding and dry pressing are the most widely used.
Debinding and sintering
In addition to the forming technology based on dry pressing, products formed by other processes need to undergo debinding and sintering treatment before entering the furnace because other processes except dry pressing will add a certain proportion of plasticizers to the zirconia powder during forming. These plasticizers must be removed after product forming, or they will seriously affect the quality of the sintered product. The main plasticizer is paraffin wax and other high polymers.
6、How to choose the appropriate zirconia products:
The following methods can be used to select high-quality zirconia ceramic components:
6.1 Firstly, observe whether the hardness of the zirconia ceramic component meets the standard, as well as its wear resistance, thermal conductivity, chemical stability, and corrosion resistance.
6.2 Secondly, the zirconia ceramic component must have good refractory properties because it is a high-temperature resistant ceramic, so it should be able to withstand at least 1000 degrees Celsius.
6.3 Thirdly, the zirconia ceramic component must have good chemical stability and high resistance to acid corrosion under high-temperature conditions.
6.4 Finally, the density of the product must be high, and it should have high biocompatibility.
7、How to choose the appropriate zirconia ceramic manufacturer:
7.1 Look for a manufacturer with high-quality production equipment.
Due to the high difficulty of zirconia ceramic manufacturing, high-precision and high-quality imported production equipment is required, and the cost of investment is also high. Therefore, when selecting a zirconia ceramic manufacturer, it is recommended to survey their production equipment on-site and inspect whether they have high-precision production equipment.
7.2 Look for a manufacturer with excellent technical processes.
The quality of the manufacturing process of zirconia ceramic products is also an important factor that affects product quality. Therefore, when selecting zirconia ceramic products, it is also necessary to consider whether the manufacturer has a matching production process, and only excellent production processes can produce high-quality zirconia ceramic products. Therefore, the manufacturer’s proficiency in zirconia ceramic production processes is also a critical factor that users should pay attention to when choosing a manufacturer.
7.3 Look for a manufacturer with high-quality materials.
High-quality zirconia ceramic products have advantages in wear resistance, corrosion resistance, high-temperature resistance, and acid-alkali resistance. However, only high-quality ceramic raw materials can produce high-quality zirconia ceramic products. Therefore, when selecting products, users should also inspect whether the materials used by the manufacturer meet the standards.
8、Application fields of zirconia ceramics
Zirconia ceramics have unique chemical bonds and crystal structures, making them useful in high-temperature, electrical, mechanical, and optical fields. They can be broadly divided into two application fields: structural ceramics and functional ceramics. In structural ceramics, zirconia ceramics are widely used due to their high toughness, high bending strength, high wear resistance, excellent insulation performance, and thermal expansion coefficient close to that of steel. Examples of applications include Y-TZP grinding balls, dispersants and grinding media, nozzles, ball valve seats, zirconia molds, micro fan shafts, optical fiber pins, optical fiber sleeves, drawing dies and cutting tools, wear-resistant tools, clothing buttons, watch cases and straps, bracelets and pendants, ball bearings, lightweight golf club heads, and other room temperature wear-resistant components. In functional ceramics, zirconia ceramics are used for their excellent high-temperature resistance as induction heating tubes, refractory materials, heating elements, etc. Zirconia ceramics also have sensitive electrical properties and are mainly used in fields such as oxygen sensors, solid oxide fuel cells (SOFCs), and high-temperature heating elements. ZrO2 has a high refractive index (N-21^22), and by adding certain coloring elements (V2O5, MoO3, Fe2O3, etc.) to ultrafine zirconia powder, it can be made into colorful translucent polycrystalline ZrO2 materials that sparkle with brilliant colors like natural gemstones, and can be made into various decorations. In addition, zirconia is widely used in fields such as thermal barrier coatings, catalyst carriers, medical care, health care, refractories, and textiles.
9、Development trends of zirconia ceramics
As the most widely used material in advanced ceramics, zirconia ceramics are experiencing the following development trends along with the development of the entire industry:
9.1 The technological level of zirconia ceramics equipment will rapidly improve:
The development of computer technology and digital control technology promotes the technological progress and rapid development of zirconia ceramics materials industry. Advanced equipment such as automatic control continuous sintering kilns, high-power and high-capacity grinding equipment, high-performance powder-making and granulating equipment, and other advanced equipment for net pressure forming have effectively promoted the overall level of the industry. Meanwhile, the production efficiency and product quality of zirconia ceramics have also been significantly improved.
9.2 The quality level of zirconia ceramics products will continue to improve:
9.3 The scale of zirconia ceramics industry will rapidly expand:
As a basic material for other industries or fields, the application and consumption of zirconia ceramics are influenced and restricted by the development level of other industries. From the application of zirconia ceramics, the scope of application is becoming wider, and the amount used is increasing, especially in the fields of mechanical equipment and chemical experiments, which will become more significant.