Rare earth is the general name of 15 lanthanide elements and 17 metal elements in the periodic table of scandium and yttrium. It is widely used in industrial production and scientific research today and is called "industrial vitamin". Using rare earths as additives, stabilizers, and sintering aids in structural ceramics can greatly improve fracture toughness, density, strength and other properties, and can also simplify production processes and reduce production costs.
1. Application in alumina ceramics
Alumina (Al2O3) ceramics are currently the most widely used structural ceramics due to their high strength, high temperature resistance, good insulation, wear resistance, corrosion resistance, and good electromechanical properties. Adding rare earth oxides such as Y2O3, La2O3, Sm2O3, etc. can improve the wettability of Al2O3 composites, reduce the melting point and porosity of ceramic materials, increase density and glass phase strength, and improve the mechanical properties of Al2O3 ceramics.
2. Application in silicon nitride ceramics
Silicon nitride (Si3N4) ceramics have excellent mechanical properties, thermal properties and chemical stability, and are one of the most promising materials in high-temperature structural ceramics. Since Si3N4 is a compound with strong covalent bonds, sintering aids such as rare earth oxides Y2O3, Nd2O3, La2O3, etc. need to be added during sintering to improve the high temperature fracture toughness of the material.
3. Application in zirconia ceramics
Zirconia (ZrO2) ceramics have high density, high melting point, high hardness and other properties, especially the bending strength and fracture toughness are the highest of all ceramics. Because the ZrO2 crystal form transformation is accompanied by a significant volume change, the scope of direct use is limited. Rare earth oxides Y2O3, Nd2O3, Ce2O3, etc. have a good inhibiting and stabilizing effect on ZrO2 phase transition, so that ZrO2 ceramic materials have good technical performance indicators, which can be used as solid electrolyte materials, oxygen ion conductor materials, etc., and are used in fuel cells, Sensors and other fields.
4. Application in silicon carbide ceramics
Silicon carbide (SiC) ceramics have the characteristics of high temperature resistance, thermal shock resistance, corrosion resistance, wear resistance, good thermal conductivity and light weight. They are commonly used high temperature structural ceramics. The strong covalent bonding characteristics of SiC determine that it is difficult to achieve sintering densification under normal conditions. Al2O3-Y2O3 is the most effective sintering aid for pressureless sintering of SiC; Y3Al5O12 is used as a sintering aid to produce SiC-YAG ceramic composites. The material can be densified and sintered at a lower temperature and is considered to be one of the most promising silicon carbide ceramic systems.
5. Application in aluminum nitride ceramics
Aluminum nitride (AlN) ceramics have high melting point, high thermal conductivity, low dielectric constant, and can withstand the corrosion of metals and alloys such as iron and aluminum. It has excellent high temperature resistance in special atmospheres and is an ideal large-scale integrated circuit. Substrate and packaging materials. Since AlN is a covalent bond, and a single sintering aid has a limited degree of lowering the firing temperature, composite additives (rare earth metal oxides and alkaline earth metal oxides) are usually used as sintering aids to form a liquid phase to promote sintering, and Reacts with oxygen impurities in AlN to improve the thermal conductivity of AlN.
6. Application in Sialon ceramics
Sialon ceramics is a kind of Si-NO-Al dense polycrystalline nitride ceramic developed on the basis of Si3N4 ceramics. Its strength, toughness and oxidation resistance are better than Si3N4 ceramics. It is especially suitable for ceramic engine parts and Other wear-resistant ceramic products. Sialon materials are not easy to sinter, and the introduction of rare earth oxides is conducive to the formation of liquid phase at a lower temperature and effectively promotes sintering. At the same time, improve the material's room temperature and high temperature performance, strengthen the material's fracture toughness and oxidation resistance.