Guides / Materials
Start From the Failure, Not the Datasheet: A Ceramic Selection Method
May 18, 2026
Most ceramic selection goes wrong in the same way. Someone picks a material from a previous project, the part cracks, and the next revision moves to a harder material, which cracks faster. Hardness is not the answer to cracking. Toughness is.
Here is a method that works, followed by the table that makes it quick.
Step 1: name the failure you are preventing
Write one sentence: “This part fails when it ______.” The useful answers cluster into six modes.
- Cracks under load, impact or clamping
- Wears against a hard or abrasive counterface
- Is attacked chemically
- Breaks down electrically or leaks current
- Cannot shed heat, or cannot block it
- Moves dimensionally with temperature or load
Almost every ceramic part in service has exactly one of these as its binding constraint. Optimising for the other five is how money is wasted.
Step 2: rank the property that prevents it
| Failure mode | Property that matters | Grades to shortlist |
|---|---|---|
| Cracking, impact, thin sections | Fracture toughness | 3Y-TZP zirconia, ATZ, silicon nitride |
| Abrasive wear | Hardness, then toughness | Silicon carbide, alumina 99.5%, ZTA |
| Chemical attack | Purity, phase purity | Sintered SiC, alumina 99.8%, zirconia |
| Dielectric breakdown | Purity, density | Alumina 99.5% and above, aluminium nitride |
| Heat removal | Thermal conductivity | Aluminium nitride, silicon carbide |
| Thermal shock | Expansion and conductivity together | Silicon nitride, then SiC |
| Deflection under load | Elastic modulus | Silicon carbide, alumina |
| Fast prototype, low stress | Machinability | Macor, Shapal, boron nitride |
Step 3: check the three properties that quietly veto a choice
Thermal expansion, if the part is joined or clamped to metal. A mismatch that no one checked is a common cause of parts that survive testing and fail in the field.
Thermal conductivity, if the part sits in a heat path. Zirconia is a thermal insulator. Putting it under something that needs cooling is a design error that no tolerance will fix.
Maximum use temperature under load, not the headline figure. Many published maximums are for unloaded service.
Step 4: sanity check against cost and availability
The best grade you cannot buy as a blank near your part size is not the best grade. Ask two questions before committing:
- Does this material exist as stock plate, rod or tube close to my envelope?
- If it does not, am I prepared to pay for pressing tooling and a firing slot, then wait?
That choice is the single biggest lever on lead time and price. It is explained in green machining or hard grinding and what drives ceramic machining costs.
A worked example
A pump component wears out in three months. The current part is alumina 96%. The instinct is to move to silicon carbide, which is harder.
Working through the method: the failure is edge chipping at the inlet, not surface wear. Toughness is the binding property, not hardness. SiC is less tough than alumina, so it would fail sooner. The right shortlist is ZTA, 3Y-TZP or silicon nitride, and the drawing also needs a chamfer at the inlet edge. See why sharp corners are the most expensive line on your drawing.
What to send a supplier
Do not send a material name you are unsure about. Send:
- The failure mode sentence from step 1
- Temperature, including cycling and rate of change
- Chemistry and cleanliness requirements
- Load, including clamping and handling loads
- Voltage, frequency and vacuum level if relevant
- Quantity now and per year
That is enough for a competent shop to propose a grade and price two options. The full RFQ checklist is in the buyer guide.
The four steps are the core of a wider path from failure mode to a grade and a specification line, set out in our guide to ceramic material selection.
Describe your part and we match it with up to 3 shops that work in these materials daily. Reply within 24 business hours.
See also: types of technical ceramics.
Frequently asked questions
What single property predicts whether a ceramic part will survive?
Fracture toughness, more often than hardness or strength. Most ceramic parts fail from a crack that started at an edge, a corner or a handling knock, not from being worn out or overloaded in a uniform way.
Can I use a metal datasheet approach for ceramics?
No. Ceramics have no meaningful yield point and they do not redistribute stress by deforming. Design around stress concentration and surface condition rather than around a safety factor on yield.
Should I send a material or a requirement to a supplier?
Send the requirement. Temperature, chemistry, load, voltage, cleanliness and the failure you are trying to avoid will get you a better grade recommendation than a name copied from a previous drawing.
Need a quote for this part?
Send the drawing. We match you with up to 3 shops that grind this grade and reply within 24 business hours.
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