Properties and Applications of Zirconia

Zirconia ceramic is an important advanced material widely used in modern high‑tech industries. With the advent of the 5G era, zirconia has become a popular choice for smartphone back covers, fingerprint sensor modules, and other structural components due to its jade‑like texture, exceptional scratch and Wear Resistance, minimal electromagnetic shielding, and excellent thermal performance.
 
1. Introduction to Zirconia
 
Zirconia ceramic, or ZrO₂, exhibits a combination of outstanding properties including high melting and boiling points, high strength with good toughness, excellent wear resistance, high surface finish, electrical insulation at room temperature, and conductivity at elevated temperatures. Pure ZrO₂ is white, while impurities may cause yellow or gray discoloration. Naturally occurring zirconia usually contains HfO₂, which is difficult to separate. Global zircon resources are estimated at approximately 19 million tons, and zirconia is typically produced by purifying zircon ores. Due to its transformation toughening mechanism, zirconia is the dominant material used in high‑end ceramics for consumer electronics.
 
Zirconia exists in three crystalline phases: monoclinic (m‑ZrO₂) at low temperatures, tetragonal (t‑ZrO₂) at intermediate temperatures, and cubic (c‑ZrO₂) at high temperatures. These phases are stable within specific temperature ranges and can transform into one another with changes in temperature.
 
2. Key Properties
 
Zirconia ceramic is a new type of advanced technical ceramic, often referred to as the “noble material” of ceramics. It offers high strength, high hardness, high temperature resistance, resistance to acids and alkalis, excellent chemical stability, scratch and wear resistance, minimal electromagnetic shielding, good thermal performance, strong processability, an attractive appearance, and suitability for mass production.
 
1. High Melting Point
Zirconia has a melting point of 2715℃. Its high melting point and chemical inertness make it an excellent refractory material. For this reason, if a zirconia dental crown becomes loose, it can be easily cleaned by burning off the residual adhesive with an alcohol lamp without affecting reattachment.
2. High Hardness and Wear Resistance
Zirconia exhibits high hardness and excellent wear resistance. For comparison, cubic zirconia (synthetic diamond simulant) has a Mohs hardness of approximately 8.5, close to sapphire (9). In contrast, polycarbonate has a hardness of 3.0, tempered glass 5.5, aluminum‑magnesium alloy 6.0, and Corning Gorilla Glass 7.
3. High Strength and Good Toughness
Zirconia can achieve a strength of up to 1500MPa. Although its toughness is lower than that of some metals, it is exceptionally high for a ceramic material, with a fracture toughness range of 1–35MPa·m¹/².
4. Low Thermal Conductivity and Low Expansion Coefficient
Zirconia has the lowest thermal conductivity among common ceramics (1.6–2.03W/(m·K)), and its thermal expansion coefficient is close to that of metals. These properties make it ideal for structural applications such as smartphone components.
5. Excellent Electrical Properties
Zirconia has a dielectric constant three times that of sapphire, enabling more sensitive signal transmission, which is particularly useful for fingerprint sensor patches. As a non‑metallic material, zirconia does not shield electromagnetic signals, allowing greater flexibility in antenna design and integration, and making it well‑suited for 5G devices.
6. Typical Applications
 
Zirconia is widely used in modern industry and daily life. The main application areas are as follows:
 
1. 3C Electronics (e.g., Smartphones)
Zirconia is widely used in smartphone back covers and structural components due to its non‑magnetic properties, resistance to drop, wear, and bending, jade‑like appearance, and comfortable touch.
2. Optical Communications
Ceramic ferrules and sleeves are commonly used in fiber optic connectors. Ferrules made from high‑strength, high‑toughness ceramics can achieve high precision, long service life, and extremely low insertion and return loss.
3. Automotive Industry
Zirconia ceramics have low thermal conductivity and a relatively high thermal expansion coefficient, making them suitable for engine combustion chamber components that require good heat insulation and compatibility with metal parts. Potential applications include cylinder head liners, piston tops, and valve seats. However, due to the harsh operating conditions of engines and the significant change in ceramic strength at high temperatures, widespread commercial application in this field is still under development.