Technical ceramics is the generic term for ceramic materials that have very different properties depending on the requirement profile. Not every material is suitable for every application. We help you find the right one.
BCE SPECIAL CERAMICSTechnical Ceramics Materials: Alumina, Zirconia, Mixed Oxides, Special Materials
MATERIALSFour material classes – different properties, different applications
An overview of the application focus and limits of the four material classes:
Zirconia (ZrO₂)
Zirconia is the high-performance material among the oxide ceramics. Ceramic materials made from zirconia generally consist of zirconia and certain doped additional oxides such as Y₂O₃ or MgO. Depending on the dopant, the properties change: the dopant decisively determines the microstructure and grain structure. The high-strength ZrO₂ referred to as “ceramic steel” is the one doped with Y₂O₃ (yttria). It forms a very fine, tough microstructure in the sub-µm range and exhibits very high flexural strengths. The MgO-doped materials are less strong and have coarser grain structures.
In addition to excellent tribological properties in moving components, zirconias are also characterised by:
- Exceptional fracture toughness
- High wear resistance
- High corrosion resistance
- Low thermal conductivity
- Linear thermal expansion coefficient similar to steel
As a result, zirconias are increasingly gaining importance as structural materials for highly stressed components – including medical technology.
Application limits: Continuous operation above 900 °C, as a phase transformation sets in.
BCE grades: Z-507 (MgO-doped), Z-700, Z-700E, Z-700E-HIP, Z-700-20A (all Y₂O₃-doped). For the watch and jewellery industry, Z-700 is also available in black, blue and pink.
Data sheets: Z-507 (PDF) | Z-700 (PDF) | Z-700E (PDF) | Z-700E-HIP (PDF) | Z-700-20A (PDF)
Alumina (Al₂O₃)
Alumina is the most widely used ceramic material. This is partly due to its attractive availability in various purity grades – ranging from approx. 92% up to 99.99% – as well as its property profile: with moderate strengths, high abrasion resistance due to its very high hardness and relatively good thermal conductivity, the material is versatile. In addition, for electrical applications and high-temperature use, it offers very good electrical insulation and dielectric strength as well as very high temperature resistance up to 1,750 °C.
BCE primarily processes purity grades from 96% (A-960) to 99.99% (A-999), with the focus at 99.5% to 99.7%.
Application limits: Components under high impact or bending load – the very high hardness is accompanied by increased brittleness. However, solutions can often be found through design adaptations. Hydrofluoric acid attacks Al₂O₃.
Data sheets: A-960 (PDF) | A-997 (PDF) | A-999 (PDF) | ZTA-86/14 (PDF)
Mixed Oxide Ceramics (ATZ / ZTA)
The mixed oxide ceramics are based on mixtures of the main components Al₂O₃ and ZrO₂. Depending on the main proportion – typically 80–90% Al₂O₃, remainder ZrO₂, or conversely approx. 80% ZrO₂, remainder Al₂O₃ – different material profiles result. Materials with Al₂O₃ as the main component are called ZTA (Zirconia Toughened Alumina), the reverse is consequently called ATZ (Alumina Toughened Zirconia).
The background to the mixtures is to combine the good properties of both oxides: the high strength and toughness of zirconia with the hardness and wear resistance of alumina. With a suitable ZrO₂ content in the ZTA material, the high electrical insulation of Al₂O₃ is also retained.
These special ceramics find application in special tools (e.g. drills for medical technology and metalworking) with significant wear in the ATZ variant, and as ZTA for rigid insulation components and medical technology applications. High surface qualities ensure minimum friction wear.
Application limits: When a pure oxide class fully meets the requirement profile – mixed oxides are more expensive and complex than Al₂O₃ or ZrO₂ alone.
Special Materials: Si₃N₄, SiC, B₄C, AlN
By special materials, BCE means the non-oxide ceramic high-performance materials: silicon nitride (Si₃N₄), silicon carbide (with or without free silicon: SiSiC or SSiC), boron carbide (B₄C) and aluminium nitride (AlN). These have different special properties that must be tailored to the respective application.
Silicon nitride (Si₃N₄) is partly similar to zirconia in terms of comparatively high strength and toughness, but differs from the oxide materials through its lower thermal expansion combined with good thermal conductivity.
The carbides (SiC, B₄C) with their extreme hardness tend to be closer to Al₂O₃. SiC is chemically resistant to almost all acids and alkalis – except concentrated potassium hydroxide and hydrofluoric acid.
Aluminium nitride (AlN) has a special position due to its very high thermal conductivity (approx. 150–180 W/mK) combined with electrical insulation – used in high-performance electronics and in crucibles.
Application limits: More complex in processing and manufacturing than oxide ceramics. Only use when the special properties are actually required.
BCE grades: N-105 (hot-pressed silicon nitride)
Data sheets: N-105 (PDF)
COMPARISON TABLEAll key values at a glance
The BCE comparison table lists hardness, flexural strength, fracture toughness, thermal expansion, electrical insulation and operating temperature for all materials – as a starting point for material selection.
KEY FACTSTechnical key values at a glance
1,100 MPa
Flexural strength ZrO₂ Z-700E (Y-TZP)
1,800 HV
Hardness Al₂O₃ A-997/A-999
up to 1,650 °C
Maximum operating temperature Al₂O₃ in air
850 MPa
Flexural strength Si₃N₄ N-105 (hot-pressed)
2,500 HV
Hardness SiC SC-200 – hardest material in the BCE range
Still unsure whether ceramics are the right choice for your component? Briefly describe the requirement – medium, temperature, load. We will give you a professional assessment.
FAQFrequently asked questions about material selection in technical ceramics
What is the difference between alumina and zirconia?
Al₂O₃ is the most widely used ceramic material: good electrical insulation, temperature resistance up to 1,650 °C, economical in various purity grades. ZrO₂ is mechanically stronger: flexural strength up to 1,100 MPa (Z-700E), higher fracture toughness, biocompatible. The thermal expansion coefficient of ZrO₂ is close to steel, which facilitates composite constructions. For continuous operation above 900 °C, Al₂O₃ is the right choice – ZrO₂ tends to phase transformation at these temperatures.
When is a mixed oxide useful – and when is Al₂O₃ or ZrO₂ sufficient?
Mixed oxides such as ATZ and ZTA combine the strength and toughness of zirconia with the hardness and wear resistance of alumina. ATZ (approx. 80% ZrO₂) is suitable for heavily wear-loaded tools, ZTA (80–90% Al₂O₃) for rigid insulation components with increased toughness. If a pure oxide grade fully meets the requirement profile, it is the more economical choice – mixed oxides are more complex to manufacture.
When are special materials such as SiC or Si₃N₄ necessary?
When oxide ceramics reach their limits: SiC for combined corrosion and wear loading by aggressive media – resistant to almost all acids and alkalis, except concentrated potassium hydroxide and hydrofluoric acid. Si₃N₄ for high strength and toughness combined with low thermal expansion and good thermal conductivity, e.g. in rolling bearing technology. Special materials are more expensive in raw material and machining – their use is only justified when the property is actually required.
How does the material selection affect manufacturing costs?
Directly and considerably. Special materials such as SiC or Si₃N₄ are more expensive in raw material and machining than oxide ceramics. Higher purity grades of Al₂O₃ increase the material price but improve insulation value and purity requirements. Complex geometries increase grinding effort regardless of the material. The most economical choice is not the cheapest material, but the material that meets the load profile with the least overdimensioning.
Technical clarity from the start.
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