High-Purity Alumina Ceramics: A Critical 'Pro-Ceramic' Player in Four Key Sectors, Showcasing the Allure of Purity
High-purity alumina ceramic is an important ceramic material primarily composed of high-purity, ultrafine alumina as the main raw material, with α-Al2O3 as the principal crystalline phase. Due to its excellent properties such as high mechanical strength, great hardness, high-temperature resistance, and corrosion resistance, high-purity alumina Ceramics Are widely used in machinery, electronics, integrated circuits, medicine, and other fields.
It is understood that semiconductor equipment utilizes a large number of precision Ceramic Components, which can account for over 10% of the cost of semiconductor equipment. Among these, alumina ceramics are commonly used for precision components.
For instance, in semiconductor etching equipment, the chamber materials are a major source of wafer contamination. The extent to which plasma etching affects these materials determines wafer yield, quality, process stability, and more. Therefore, researching and developing highly etch-resistant chamber materials has become a challenging task in the semiconductor integration industry and plasma etching technology. Currently, high-purity Al2O3 coatings or Al2o3 Ceramics are mainly used as protective materials for etching chambers and internal components. Besides the chamber, components such as gas nozzles, gas distribution plates, and wafer fixation rings in plasma equipment also require high-purity alumina ceramics. Another example is in the wafer polishing process, where alumina ceramics are widely used in polishing plates, polishing pad conditioning platforms, vacuum chucks, and more.
High-purity alumina ceramics exhibit excellent mechanical properties. Those prepared by pressureless sintering can achieve a flexural strength of about 250 MPa, while those prepared by hot-pressing sintering can reach a flexural strength of 500 MPa and a hardness of 9 GPa (Mohs hardness). Leveraging these properties, high-purity alumina ceramics can be used as grinding wheels, ceramic nails, etc., with the most widespread applications being high-purity alumina ceramic cutting tools and high-purity alumina ceramic balls. However, due to their relatively poor fracture toughness and thermal shock resistance, it is often necessary to introduce a second phase, such as ZrO2, into alumina to improve the toughness and thermal shock resistance of high-purity alumina ceramic materials. Additionally, by refining the grain size and producing high-purity alumina ceramics with small and uniformly distributed grains, their strength and toughness can also be significantly enhanced to some extent.
High-purity alumina ceramics have low high-frequency dielectric loss and excellent insulation properties, making them suitable for manufacturing insulating devices, ceramic substrates, and transparent alumina ceramics. Among these, ceramic substrates and transparent alumina ceramics are widely used, finding increasing applications in special optical instruments, lighting equipment, space satellite equipment, and more.
In terms of ceramic substrates, alumina ceramic substrates are the most widely used base material in the contemporary electronic information industry, serving as the foundational material for integrated circuit chips. For example, in LED lighting, the mainstream substrate has a coefficient of thermal expansion (CTE) of 14–17×10⁻⁶/K. Under significant temperature differences or abrupt temperature changes, the PCB expands more drastically than the chip package, leading to desoldering issues. In this context, the CTE of alumina ceramic substrates is closer to that of chips, effectively avoiding such problems.
Regarding transparent alumina ceramics, since Dr. Coble first developed and prepared transparent alumina ceramics (also known as transparent polycrystalline alumina ceramics) in 1959, research and applications of transparent alumina ceramics have garnered widespread attention. Compared to glass, transparent alumina ceramics offer higher strength, hardness, and toughness, along with superior surface wear resistance that glass cannot match. Compared to single-crystal materials, transparent alumina ceramics require lower preparation temperatures and shorter production cycles. It is precisely these properties that make transparent alumina ceramics a research hotspot, enabling their extensive application in optics, special instrument manufacturing, lighting, electronic technology, high-temperature technology, national defense, military, aerospace, and more. For instance, leveraging the light transmittance, corrosion resistance, and high-temperature stability of transparent alumina ceramics, they can be used to manufacture luminous arc tubes for high-pressure sodium lamps.
Biomedical materials can repair human bodily functions without causing adverse effects. Healthcare organizations impose very strict requirements on biomedical materials, demanding not only biocompatibility but also non-toxicity, environmental friendliness, durability, and other characteristics. Due to their excellent biocompatibility, mechanical properties, and chemical stability, high-purity alumina ceramics do not cause rejection reactions when implanted in the human body. They are widely used in the production of artificial bones, bolts, artificial joints, etc., and have gained recognition in both clinical and research settings.
The distinctive properties and applications of high-purity alumina ceramics, which set them apart from ordinary alumina ceramics, stem from their high purity. At the same time, stringent requirements for particle size, dispersity, etc., pose challenges for the preparation of high-purity alumina powders.