How does yttria stabilized zirconia?

Yttrium oxide stabilized zirconia is a high performance engineering ceramic material. It has high wear resistance, corrosion resistance and thermal stability. Yttrium oxide stabilized zirconia is mainly used in high temperature, chemical and wear resistant applications such as aerospace, energy, medical and automotive.

The preparation process of yttrium oxide stabilized zirconia is relatively complex and requires special chemical treatment and heat treatment. By adding yttrium oxide to zirconium oxide and subjecting it to high temperature heat treatment, a crystal structure of yttrium oxide stabilized zirconium oxide with high particle bonding can be formed. This crystal structure has excellent mechanical strength and thermal stability.

How does yttria stabilized zirconia

Yttrium-stabilized zirconia spheres are structural ceramic materials that change the phase transition temperature range of zirconium dioxide by adding yttrium oxide to produce cubic and tetragonal crystals that are stable at room temperature. Pure zirconia is monoclinic at room temperature, also known as monoclinic powder, and becomes tetragonal when the temperature rises to about 1173°C, cubic when it rises to 2370°C, and liquid at 2690°C.

Among many ceramic materials, zirconia ceramics are increasingly preferred due to their excellent biocompatibility, high strength and high toughness. Zirconia exists as monoclinic phase (m) at room temperature and transforms into tetragonal phase zirconia when the monoclinic phase zirconia is heated to 1170°C, accompanied by a 7-9% volume shrinkage and a rapid transformation rate. During cooling, the tetragonal phase zirconia transforms into monoclinic phase zirconia (t-m) at about 950°C. This phase transformation is known as martensitic phase transformation. This phase transition is accompanied by a volume expansion of 3%-5%, which makes the ceramic material susceptible to cracking and loss of application value, so zirconia ceramics cannot be used in practice. It was later found that if some rare earth oxides were added to zirconia as stabilizers, this destructive effect could be reduced or eliminated, allowing zirconia to be stable at room temperature.

Pure zirconia ceramics are difficult to fire into dense ceramics because of the phase change that occurs during sintering and cooling, which triggers volume expansion and cracking. To eliminate this change, a stabilizer is added to the zirconium oxide to prevent the phase change from occurring. This solid solution can keep the tetragonal phase or cubic phase from phase change at room temperature and even remain stable at high temperature. The cation radius of these oxides is similar to that of Zr4+, and they have larger solubility in zirconia. The solid solution formed can stabilize the cubic or tetragonal phase zirconia in a wide temperature range, which has a good effect on the stability of material properties.

Depending on the stabilizer content in zirconia, it can be classified into fully stabilized zirconia (FSZ), partially stabilized zirconia (PSZ), and tetragonal polycrystalline zirconia (TZP).

Fully stabilized zirconia (FSZ) has the worst mechanical properties because it exists as a stable c-phase at room temperature and cannot undergo t-m phase change, which plays no role in phase change toughening. Partially stabilized zirconia ceramics have high fracture toughness due to the t-m phase toughening effect, and are known as "ceramic steels". t-phase content directly determines the performance of zirconia ceramics. TZP is a t-phase ceramic, which is sintered in the t-phase region and does not undergo phase change during cooling, maintaining several flat phases at room temperature, while giving the best overall mechanical properties. Although there are many oxides used as zirconium oxide stabilizers, past studies have shown that the best comprehensive mechanical properties among many stabilizers are yttrium oxide - zirconium oxide ceramics. At the same time, the content of yttrium oxide also directly affects the performance of ceramic materials: too high a content will form a large number of cubic phase (c-ZrO2) zirconium oxide, which is too stable zirconium oxide grains and not easy to phase change, it is difficult to play the role of phase change toughening, but will cause a decline in the mechanical properties of the material; too low content can not effectively stabilize the zirconium oxide in the tetragonal phase, but will form a large number of monoclinic phase, and lose If the content is too low, the zirconium oxide will not be effectively stabilized in the tetragonal phase.

Advantages of Yttrium Stabilized Zirconia

One is its excellent wear resistance. It is harder and stronger than many conventional metallic materials and can withstand high intensity impact and friction. This makes yttrium oxide stabilized zirconia widely used in areas where wear resistance is required, such as in the manufacture of abrasives, bearings and valves.

The second is its excellent corrosion resistance. It has high chemical stability and can resist many strong acids, bases and brines. This corrosion resistance makes yttrium oxide stabilized zirconia an ideal material choice for aerospace, chemical and food processing applications where high corrosion resistance is required.  

In addition, the high temperature stability of yttrium oxide stabilized zirconia is very good. Its high-temperature strength, coefficient of thermal expansion and thermal conductivity are higher than those of other engineering ceramics, and it can withstand stresses and deformations at high temperatures. Therefore, yttrium oxide stabilized zirconia is often the preferred material in high-temperature environments where long periods of operation are required.

Yttria stabilized zirconia applications

1. Solid Oxide Fuel Cell SOFC.

Solid oxide fuel cell is an all-solid chemical power generation device that can directly convert chemically efficient and environmentally friendly electricity stored in fuel and oxidizer at medium to high temperatures.The anode support in the SOFC system is made of Hongwu Nano U706ZRO2-8Y.It is an excellent conductor of oxygen ions and is very stable in oxidizing and recovering atmospheres. It is an ideal material for applications in solid oxide fuel cells.

2. Bioceramics, electronic ceramics, and structural ceramics.

U703ZRO2-3Y bio-grade denture has high fracture strength, high fracture toughness, high light transmission Strong jade texture and high whiteness, which can well match the color of human teeth. Perfect for manual grinders or CAD/CAM equipment.

3. Artificial gemstones, colored ceramic jewelry.

Yttrium oxide zirconia colored ceramic jewelry is close to natural diamond in hardness, lighter than metal, non-abrasive, non-discolored, non-rusting, beautiful and durable, bright and bright, textured, visually extraordinary.

4. Fire-resistant materials.

Electronic ceramic firing support mat, molten glass, metallurgical metal refractory materials using yttrium oxide stabilized zirconia as refractory materials.

5. Oxygen sensor.

Oxygen sensor is the standard configuration of the car. It is the use of ceramic sensitive elements to measure the oxygen potential in the exhaust pipe of the car, and calculate the corresponding oxygen concentration through the chemical equilibrium principle to achieve the monitoring and control of the combustion air-fuel ratio to ensure product quality and exhaust emission standards. The zirconium oxide element in the sensor is similar to the electrolyte

6. More applications.

Wear parts, thermal resistance coatings, optical fibers, collars, bushings, grinding media.

In conclusion, yttrium oxide stabilized zirconia is widely used in various fields as a high performance engineering ceramic material with excellent characteristics such as wear resistance, corrosion resistance and high temperature stability. With the continuous development of technology and changing needs, the application prospect of yttrium oxide stabilized zirconia will become more and more promising.