The four systems we work in overlap heavily on the data sheet, which is why selection conversations go wrong when they start from a table. Start from the duty instead, and the field narrows quickly.

Work through three questions in order

  • Temperature first: how hot it runs, and — more importantly — how often it is cycled. Thermal shock, not peak temperature, ends most ceramic parts in service.
  • Wear second: what removes material. Hard particles at speed, repeated impact, and galling against a mating surface point at different grades.
  • Electrical duty third: if the part has to insulate, that usually settles the choice, because the systems behave quite differently as insulators at temperature.

The four systems, one line each

  • Alumina — the default. Electrical insulation, dimensional stability and the widest availability of forms, at the lowest cost of the four.
  • Zirconia — toughness and a polished, low-friction surface. The choice for contact parts that take impact or need a smooth running face.
  • Silicon carbide — high temperature with abrasion and corrosion, plus thermal conductivity where heat has to move.
  • Silicon nitride — thermal shock resistance combined with strength at temperature. Where fast cycling would end the other grades early.

What usually decides against a system

The property table is rarely the deciding factor. What decides is whether the form you need can be made in it, whether the wall thickness is achievable, whether the volume justifies the tooling, and whether the grade is available at the size and lead time the project needs. Those practical constraints are worth raising at the enquiry stage, not after the design is frozen.

Ask for the data sheet before you design around a number

Property values for any of these systems move with grade, purity and porosity. The figures published in general reference tables describe a family, not the grade you will receive. Before a design is committed, ask for the data sheet for the specific grade being quoted.

This note is selection guidance. It states no figures and is not a specification. Grade-specific properties are issued on the material data sheet with a quotation.