Ceramic tubes protect, isolate and carry. They serve as thermocouple sheaths, furnace muffles, insulating bushes and fluid paths where metal would corrode, creep or conduct.
Zirconia tubes are used as oxygen sensor electrolytes and as insulating sleeves in high-temperature assemblies. Their low conductivity of 2-3 W/m·K also makes them useful thermal breaks, and at temperature the stabilised structure carries the ionic conduction a sensor depends on.
Yttria-stabilised zirconia is the toughest of the engineering oxides, with 8-10 MPa·m½ fracture toughness and flexural strength to 1200 MPa. It absorbs the impact and side loads that would crack alumina, and it carries the lowest thermal conductivity of the structural ceramics here.
Two limits apply. Continuous service above roughly 800-1000°C destabilises the metastable tetragonal phase, and moisture between 200 and 300°C can trigger low-temperature degradation, so stabiliser grade is matched to the duty.
Specifications
| Outer diameter | 3-150 mm |
| Inner diameter | 1-120 mm |
| Length | up to 600 mm |
| Minimum wall thickness | 0.5 mm |
| Concentricity | 0.02 mm |
| Bore finish | Ra 0.4 µm, honed Ra 0.2 µm |
| Ends | square cut, chamfered, flanged or closed one end |
Zirconia Properties
| Composition | Yttria-stabilised zirconia (Y-TZP) |
| Density | 6.00-6.05 g/cm³ |
| Vickers hardness | 1200-1350 HV |
| Flexural strength | 900-1200 MPa |
| Fracture toughness | 8-10 MPa·m½ |
| Max. service temperature | 800-1000°C |
| Thermal conductivity | 2-3 W/m·K |
| Thermal expansion (20-1000°C) | 10.0 ×10⁻⁶/K |
Machining and Tolerances
Tubes are extruded, isostatically pressed or slip cast depending on size and quantity, then ground on the outside and honed internally. Long thin-wall tubes are the most distortion-prone parts we make, so we rough grind, allow the part to relax, then finish grind.
Where It Is Used
- Thermocouple protection sheaths and furnace muffles
- Insulating bushes through heated panels and vacuum chambers
- Fluid and slurry transport in corrosive or abrasive service
- Lamp, laser and UV equipment bodies
- High-voltage insulators and standoffs
Frequently Asked Questions
What is the thinnest wall you can produce?
0.5 mm is the practical floor for most materials and lengths. Below that, yield drops sharply during firing and grinding, so we review the drawing and usually suggest thickening the wall or shortening the tube.
Can you supply closed-end tubes?
Yes. Closed one end, hemispherical closed ends and reduced-tip ends for thermocouple sheaths are all produced, either formed during shaping or ground after firing.
