High-Purity Alumina Ceramics: A Vital Player in Four Key Fields, Showcasing the Allure of 'Purity'

High-purity alumina Ceramics Are important ceramic materials primarily composed of high-purity, ultrafine alumina as the raw material and α-Al2O3 as the main crystal phase. Due to their excellent properties such as high mechanical strength, high hardness, high-temperature resistance, and corrosion resistance, high-purity alumina ceramics are widely used in various fields including machinery, electronics, integrated circuits, and medicine.

It is understood that semiconductor equipment utilizes a significant number of precision ceramic components, which can account for over 10% of the equipment's cost. Among these, alumina ceramics are commonly used for precision parts. For instance, in semiconductor etching equipment, the chamber materials are a major source of wafer contamination. Their resistance to plasma etching directly impacts wafer yield, quality, and the stability of the etching process. Therefore, developing highly etch-resistant chamber materials is a critical challenge in the semiconductor industry and plasma etching technology. Currently, high-purity Al2O3 coatings or Al2o3 Ceramics are primarily used as protective materials for etching chambers and internal components. Beyond the chamber itself, components like gas nozzles, gas distribution plates, and wafer clamping rings in plasma equipment also utilize high-purity alumina ceramics. Similarly, in wafer polishing processes, alumina ceramics are widely used for polishing plates, polishing pad conditioners, and vacuum chucks.

High-purity alumina ceramics possess excellent mechanical properties. Those prepared by pressureless sintering can achieve a flexural strength of approximately 250 MPa, while those prepared by hot-pressing sintering can reach flexural strengths of up to 500 MPa and a hardness of 9 GPa (Mohs scale). Leveraging these characteristics, they are used in grinding wheels and ceramic nails, 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, a second phase, such as ZrO2, is often introduced into the alumina to improve these properties. Furthermore, refining the grain size to produce high-purity alumina ceramics with fine and uniformly distributed grains can also significantly enhance their strength and toughness.

High-purity alumina ceramics exhibit low high-frequency dielectric loss and excellent insulation properties, making them suitable for insulating devices, ceramic substrates, and transparent alumina ceramics. Among these, ceramic substrates and transparent alumina ceramics are widely applied, finding increasing use in special optical instruments, lighting equipment, and space satellite equipment.

Regarding 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, mainstream substrates have a coefficient of thermal expansion (CTE) of 14–17×10⁻⁶/K. Under significant temperature differences or rapid 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 the chips, effectively avoiding such problems.

In the area of transparent alumina ceramics, since Dr. Coble first developed and prepared transparent alumina ceramics (also known as transparent polycrystalline alumina ceramics) in 1959, their research and application have garnered widespread attention. Compared to glass, transparent alumina ceramics offer higher strength, hardness, and toughness, along with superior wear resistance. Compared to single-crystal materials, they require lower preparation temperatures and shorter production cycles. These advantages make transparent alumina ceramics a research hotspot, leading to their extensive application in optics, special instrument manufacturing, lighting, electronics, high-temperature technology, national defense, military, and aerospace. For instance, leveraging their translucency, corrosion resistance, and high-temperature stability, transparent alumina ceramics are used to manufacture arc tubes for high-pressure sodium lamps.