Spinel REFR
Grade
REFR = refractory-grade spinel
Low-cost porous form for cement-kiln transition zones, steel-ladle linings and slag-resistant castables.
Values for the REFR condition
Other Spinel tempers and conditions
Spinel is listed in 4 conditions; see the grade overview at Spinel.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SINT-DENSEDefault pressureless-sintered dense polycrystalline spinel (opaque, >99 % TD) | Default technical-ceramic form: dense opaque spinel parts for semiconductor chamber components, kiln furniture and corrosion-exposed structural ceramics. | — | — | — | 1,350 HV | 15 W/m·K |
transparent spinel, hot-pressed + HIP optical grade | Pick for visible-to-MWIR windows, missile domes and transparent armour where sapphire is too costly or too anisotropic. | — | — | — | 1,400 HV | 15 W/m·K |
Single-crystal spinel | Choose for epitaxial substrates (GaN, SOS-type), UV–IR laser windows and where zero grain-boundary scattering is required. | — | — | — | 1,450 HV | 24 W/m·K |
REFRThis page Refractory-grade spinel | Low-cost porous form for cement-kiln transition zones, steel-ladle linings and slag-resistant castables. | — | — | — | — | 6 W/m·K |
What is Spinel REFR?
Spinel REFR is Spinel in the REFR grade — low-cost porous form for cement-kiln transition zones, steel-ladle linings and slag-resistant castables. Spinel REFR has a tensile strength of 120 MPa (17.4 ksi), stronger than 51% of ceramic grades. The elastic modulus is 100 GPa (14.5 Msi). Spinel REFR has a density of 3 g/cm³ (0.108 lb/in³), lighter than 75% of ceramic grades. It melts at 2,135°C (3,875 °F). SINT-DENSE is the default condition FabDigit quotes; REFR is available on request or by drawing note.
Advantages
- High service temperature — 1,800°C (3,272 °F), better than 92% of ceramic grades
- Easy to machine — 15/100, better than 81% of ceramic grades
- Lightweight — 3 g/cm³ (0.108 lb/in³), better than 75% of ceramic grades
Limitations
- Hard to polish — 20/100, worse than 99% of ceramic grades
Spinel REFR properties
Typical room-temperature values for Spinel REFR; 12 are specific to this condition. Other listed values are Spinel reference data and may not represent this condition. Bars are the position among ceramic grades.
Physical5
Spinel REFR has a density of 3 g/cm³ (0.108 lb/in³), lighter than 75% of ceramic grades. It melts at 2,135°C (3,875 °F).
Mechanical11
Spinel REFR has a tensile strength of 120 MPa (17.4 ksi), stronger than 51% of ceramic grades. The elastic modulus is 100 GPa (14.5 Msi).
Thermal5
Spinel REFR is rated for continuous service to 1,800°C (3,272 °F). It conducts heat at 6 W/m·K (3.47 BTU/hr·ft·°F), worse than 61% of ceramic grades. Thermal expansion is 6 µm/m·K (3.33 µin/in·°F).
Electrical5
Spinel REFR is an electrical insulator with a dielectric strength of 16 kV/mm (406.4 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental2
Corrosion resistance is excellent (85/100), better than 69% of ceramic grades.
Sustainability4
Producing a kilogram of Spinel REFR takes about 75 MJ of energy and emits 6.5 kg of CO₂ — less than 69% of ceramic grades. Typical recycled content is 0%.
Manufacturability3
Spinel REFR's machinability is poor (15/100, better than 81% of ceramic grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Spinel REFR
Is Spinel easy to machine?
Green machining before firing is the economical route; fired parts require diamond grinding, lapping and ultrasonic/laser drilling with light passes to avoid subsurface damage.
Can Spinel be welded?
Not weldable — join by active-metal brazing (Ti/Ag-Cu), glass frit sealing or metallised Mo-Mn plus Ni plating for vacuum-tight assemblies.
Can Spinel be formed, bent or molded?
Uniaxial/isostatic pressing, slip or tape casting and injection moulding of fine MgAl2O4 powder; transparent grades need vacuum sintering or hot pressing followed by HIP at 1750–1900 °C / 150–200 MPa; allow ~15–18 % firing shrinkage.
What surface finishes work on Spinel?
Diamond lapping then colloidal-silica or CeO2 polishing gives optical λ/10 flatness and <1 nm Ra; AR coatings are applied for IR window use, and no anodising/plating is applicable.
Spinel chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| MgOstoichiometric MgO·Al2O3; Al-rich (MgO·1.5–2Al2O3) grades are used for transparent and refractory products | 27 – 29.5 | 28.3 |
| LiFsintering aid used in hot-pressed transparent grades; removed/volatilised during HIP | 0 – 1 | 0.5 |
| SiO2+CaO+Fe2O3 (impurities)≤200 ppm total for optical grades | 0 – 0.5 | 0.1 |
| Al2O3 | ≥ 70.5 (balance) | — |
Spinel REFR — frequently asked
What is Spinel REFR used for?
Spinel REFR is typically used for transparent armor/windows, refractory linings, IR domes and molten metal handling refractories. In short: transparent structural ceramic; optically isotropic cubic oxide; good thermal shock resistance.
What is the tensile strength of Spinel REFR?
Spinel REFR has a typical tensile strength of 120 MPa (17.4 ksi) — stronger than 51% of ceramic grades. Strength varies by condition: see the 4 listed tempers.
Is Spinel REFR easy to machine?
Not especially — machinability is rated poor (15/100, better than 81% of ceramic grades). Green machining before firing is the economical route; fired parts require diamond grinding, lapping and ultrasonic/laser drilling with light passes to avoid subsurface damage.
Can Spinel REFR be welded?
Not weldable — join by active-metal brazing (Ti/Ag-Cu), glass frit sealing or metallised Mo-Mn plus Ni plating for vacuum-tight assemblies.
What surface finishes work on Spinel REFR?
Diamond lapping then colloidal-silica or CeO2 polishing gives optical λ/10 flatness and <1 nm Ra; AR coatings are applied for IR window use, and no anodising/plating is applicable.
Can Spinel REFR be formed, bent or molded?
Uniaxial/isostatic pressing, slip or tape casting and injection moulding of fine MgAl2O4 powder; transparent grades need vacuum sintering or hot pressing followed by HIP at 1750–1900 °C / 150–200 MPa; allow ~15–18 % firing shrinkage.
What is the maximum service temperature of Spinel REFR?
Spinel REFR is rated for continuous use to about 1,800°C (3,272 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASM Engineered Materials Handbook Vol.4: Ceramics and Glasses — ASM International (1991)
- Transparent Spinel Ceramic Window Material Data — Surmet / II-VI optical ceramics datasheets (2022)
- Technical Ceramics Material Properties — Spinel and Oxide Ceramics — CoorsTek / Kyocera (2023)
- ACerS-NIST Phase Equilibria Diagrams — MgO–Al2O3 system — American Ceramic Society / NIST (2018)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.