Nitride Ceramics
Nitride ceramics are covalent compounds of nitrogen with silicon, aluminum or boron, and each is bought for a different property. Silicon nitride combines 700–1,000 MPa flexural strength with a low expansion (about 3 ppm/K) that lets it survive a quench from 800 °C; aluminum nitride conducts heat at 170 W/m·K or better while insulating like alumina; hexagonal boron nitride is soft enough to machine with steel tools, is not wetted by molten metals and stays stable past 2,000 °C in inert gas.
Popular nitride ceramic grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| Silicon Nitride | 700 | 450 | 3.22 | Not recommended | Not recommended | Thermal shock, bearings, hot loaded parts |
| Aluminum Nitride | 320 | 200 | 3.29 | Not recommended | Not recommended | Insulating substrate that conducts heat |
| Boron Nitride | 50 | 35 | 2 | Excellent | Not recommended | Machinable, non-wetting crucibles and nozzles |
| Sialon | — | 350 | 3.25 | Not recommended | — | Sheaths and tubes in molten non-ferrous metal |
| CBN | — | — | 3.48 | Not recommended | — | Abrasive and inserts for hardened steel |
| TiN | — | — | 5.22 | Not recommended | — | Hard gold-coloured coating on tools |
| AlN | — | 200 | 3.26 | Not recommended | — | 180 W/m·K dielectric ceramic |
All 7 nitride ceramic grades
Choose nitride ceramics for
Bearings, rotors and pins that run hot and see sudden temperature change; thermocouple sheaths and tubes in molten aluminum or zinc; power-electronics substrates and heat spreaders that must insulate; crucibles, nozzles and plasma-facing insulators machined from boron nitride; and grinding or hard-turning tools based on cubic boron nitride.
Look elsewhere when
Cost matters more than thermal shock (Alumina 96 does most insulator and wear jobs for a fraction of the price), the part needs the toughness of Zirconia Y-TZP at room temperature, service is above 1,400 °C in air or the abrasive is very hard (Silicon Carbide), the part sits in water or steam (AlN hydrolyzes slowly, boron nitride grades with an oxide binder absorb moisture), or a large complex shape is needed in small quantity (Macor or a graphite grade).
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Nitride ceramic by application
- Bearings and rolling elements
- Silicon Nitride balls and rollers: 60 % lighter than steel, no galling, run without lubrication at temperatures that would soften bearing steel, and electrically insulating in hybrid bearings for motors.
- Heat-conducting insulators
- Aluminum Nitride substrates and spacers for IGBT modules, RF power and laser diodes — thermal expansion near silicon, dielectric strength around 15 kV/mm.
- Molten-metal handling
- Sialon and Silicon Nitride for thermocouple sheaths, riser tubes, heater tubes and ladle parts in aluminum; Boron Nitride for break rings, crucibles and release coatings that the melt will not wet.
- Machinable one-off insulators
- Boron Nitride machines dry with carbide or high-speed steel to ±0.02 mm and needs no firing — choose it for fixtures, nozzles and plasma-facing parts in ones and tens.
Working with nitride ceramic
- Forming & sintering
- Silicon nitride and Sialon are pressed or injection-molded and gas-pressure or hot-pressed at 1,700–1,900 °C in nitrogen; aluminum nitride is tape-cast for substrates or pressed and sintered at about 1,800 °C. Shrinkage is 15–20 %, so as-fired tolerance is about ±1 % and precision surfaces are ground.
- Grinding & lapping
- Dense silicon nitride and AlN are finished only with diamond — cylindrical and surface grinding to ±0.005 mm, bearing balls lapped to grade 5 sphericity. Hexagonal boron nitride is the exception: turned, milled, drilled and tapped with ordinary tooling, dry, with dust extraction.
- Joining & sealing
- AlN is metallized (thin-film Ti-W or direct-bonded copper) and brazed or soldered to copper for power modules. Silicon nitride is brazed with active-metal fillers or joined mechanically — shrink fits and clamped joints with compliant layers work best. Boron nitride is clamped or cemented, not brazed.
- Tolerances & design rules
- Load in compression, radius corners at 0.5 mm or more, and keep nitride sections above 1 mm. Store AlN and oxide-bonded boron nitride dry; specify a pure or calcium-borate-free BN grade for vacuum and high-humidity use.
Other ceramic series
Nitride Ceramics — frequently asked
What is nitride ceramic?
Nitride ceramics are covalent compounds of nitrogen with silicon, aluminum or boron, and each is bought for a different property. Silicon nitride combines 700–1,000 MPa flexural strength with a low expansion (about 3 ppm/K) that lets it survive a quench from 800 °C; aluminum nitride conducts heat at 170 W/m·K or better while insulating like alumina; hexagonal boron nitride is soft enough to machine with steel tools, is not wetted by molten metals and stays stable past 2,000 °C in inert gas.
Which grade of nitride ceramic should I use?
Silicon Nitride for anything that is hot, loaded and thermally cycled: bearing balls and rollers, welding locator pins, glow plugs, molten-aluminum handling, cutting inserts for cast iron. Sialon is the same structural family with aluminum and oxygen in the lattice — a little cheaper to sinter, better against molten non-ferrous metals, the usual choice for thermocouple sheaths and riser tubes. Aluminum Nitride (also listed as AlN) when the insulator must pull heat out of a power device — substrates, heater plates, laser-diode mounts. Boron Nitride for crucibles, break rings, nozzles and one-off insulators that must be machined to size, and CBN when the requirement is a grinding abrasive or insert for hardened steel; TiN is a coating rather than a bulk part.
Which grade of nitride ceramic is the strongest?
Silicon Nitride has the highest yield strength in the series at 700 MPa; Aluminum Nitride follows at 320 MPa. Values are for each grade's default condition.
Which grade of nitride ceramic is easiest to machine?
Boron Nitride (machinability excellent, 85/100), then TiN (8/100).
Silicon nitride or Sialon?
They share structure and most properties: both around 700–1,000 MPa flexural strength, toughness 6–7 MPa·√m and service to about 1,200 °C. Sialon dissolves alumina into the silicon nitride lattice, which makes it easier to sinter without pressure (cheaper large shapes) and more resistant to molten aluminum and zinc, so it dominates in foundry sheaths and tubes. Pure silicon nitride keeps the edge in bearing grades and precision components where finer grain and higher thermal-shock resistance matter.
Why choose aluminum nitride over alumina or beryllia?
Thermal conductivity: AlN carries 170–200 W/m·K against about 25 for 96 % alumina, so a power device on AlN runs cooler by tens of degrees. It also matches the expansion of silicon (4.5 ppm/K) better than alumina (7–8 ppm/K), which keeps large die attaches from cracking. Beryllia conducts even better (250 W/m·K) but its dust is toxic and it is restricted in most markets; AlN is the practical substitute.