Zirconia

• Material composition

Zirconia (ZRO₂) ceramic substrate is mainly composed of zirconia. By adding stabilizers (such as Y₂O₃, MGO, CAO, etc.), the crystal phase transformation is inhibited to form a stable cubic phase or partially stable phase structure. Common types include:

Some stable zirconia (PSZ), such as Y₂O₃ (3-5 MOL%), improves fracture toughness through phase transformation toughening mechanism, and magnesium oxide (MGO) or calcium oxide (CAO) inhibits the transformation of cubic phase to monoclinic phase at high temperature to avoid cracking caused by volume expansion.

Square zirconia polycrystalline ceramic (TZP): Y₂O₃ content 2-3 MOL%, with ultra-high strength and toughness.

Fully stable zirconia (FSZ): Y₂O₃ content is more than 8 MOL%, high temperature resistant but low toughness.

Sintering aids: such as silica (SIO₂) and alumina (AL₂O₃), reduce the sintering temperature to 1400~1600℃, and optimize the grain size (usually 0.5~5ΜM)

• Manufacturing process

1. Raw material preparation:

High purity zirconia powder (purity> 99.9%) is mixed with stabilizers (such as Y₂O₃) and refined to nanometer level (particle size <100 NM) by wet ball milling.

2. Forming process:

Dry pressing: the green body is made by high pressure (50-200 MPA), suitable for simple shape substrate, the pressure is usually 50~200 MPA.

Injection molding: used for complex shapes (such as dental restorations), polymer adhesives need to be added.

Flow forming: prepare thin film substrate (the thickness can be as low as 50 ΜM).

3. Sintering process:

Atmospheric sintering: Sintering at 1350-1550℃ to form dense ceramics (density ≥ 6.0 G/CM³).

Hot pressing sintering: pressure 10~50 MPA, temperature 1300~1500℃, to obtain a dense structure close to the theoretical density (≥99%).

Hot static pressure (HIP): high temperature (1400℃) and high pressure (100-200 MPA) treatment to eliminate internal defects, the density can reach 90%~95% of the theoretical value

4. Post-processing:

Precision grinding and polishing: surface roughness can reach RA<0.01 ΜM (mirror grade).

Surface metallization: sputtering of TI/PT/AU or screen printing of thick film electrodes for electronic connections.

• Material properties

| function           | Values/characteristics                     | Advantage scenarios

| Fracture toughness | 6-12 MPA·M¹/² (2-4 times that of alumina) | Impact and crack resistance

| high-melting-point          |2700℃                           | Long-term working temperature can reach 1000℃

| Bending strength | 800-1500 MPA (3-5 times that of alumina) | High load-bearing structural parts

| hardness           | 12-13 GPA (near sapphire)          | Wear and scratch resistant

| heat conductivity         | 2-3 W/(M·K)                     | Low heat conduction, suitable for insulation scenarios

| Thermal expansion coefficient | 10-11×10⁻⁶/℃                    | Match with metal to reduce thermal stress

| Dielectric constant | 25-30 (1 MHZ)                  | Energy storage applications in high frequency filters

| Biocompatibility | ISO 10993 certification                   | Safety of human implants

Corrosion resistance | Resistance to strong acid (except HF) and molten metal erosion | chemical and metallurgical extreme environment

• High matching industries
• Biomedical: artificial joints, dental restorations, surgical instruments.
• Automotive industry: oxygen sensor, turbocharger heat resistant parts.
• High-end electronics: 5G mobile phone backplane, MEMS sensor substrate.
• Aerospace: structural components and engine thermal barrier coatings in high temperature environment.
• Chemical equipment: corrosion resistant reactor, electrolytic cell assembly.
• Advantages of industry application technical indicators

1. Biomedical:

Advantages: high toughness, biological inertness, avoid the rejection reaction of traditional metal implants.

Indicators: artificial hip joint life>20 years, crown bending strength>1200 MPA.

2. High temperature sensor:

Advantages: temperature resistance> 800℃ (oxidation environment), suitable for engine oxygen sensor, high temperature probe.

Case: Automotive exhaust oxygen sensor (ZRO₂ based electrolyte), response time <50 MS.

3. Consumer electronics:

Advantages: high hardness (Moissan hardness 8.5) and aesthetic, used in mobile phone backplane, smart wearable devices.

Indicator: 40% improvement in anti-fall performance (compared to glass backplane).

4. Precision machinery:

Advantages: low thermal expansion coefficient is close to that of metal, used in optical fiber connectors and bearing components.

Case: Ceramic bearings in semiconductor equipment, life extended by three times.

5. Energy and chemicals:

Advantages: resistant to corrosion by molten metals (such as aluminum, copper), used in electrolytic cell lining, fuel cell separator.

• Compare other ceramic substrates

| Material | Fracture toughness (MPA·M¹/²) | Thermal conductivity [W/ (M·K)] | Typical application scenarios

| Zirconia ceramics | 6-12                 | 2-3               | Biomedical, wear parts

| Aluminum oxide ceramics | 3-4                  | 20-30             | General insulation and heat dissipation substrate

Aluminum nitride ceramics | 2-3                  | 160-260           | High power heat dissipation module

| Silicon carbide ceramics | 4-5                  | 120-200           | Ultra-high temperature structural components

Zirconia ceramic substrates, with their ultra-high strength, fracture toughness, and biocompatibility, hold an irreplaceable position in medical, precision machinery, and high-temperature sensing fields. Their disadvantages include low thermal conductivity (not suitable for heat dissipation scenarios) and high dielectric constant. However, through material design (such as doping modification and composite processes), they can be further extended to new energy and advanced electronics sectors. With the advancement of precision manufacturing technologies (such as 3D printing of zirconia), their applications in customized medical devices and miniaturized electronic components will continue to grow.