Spinel
Spinel (MgAl2O4) is a cubic magnesium aluminate ceramic supplied as dense sintered, transparent HIP'd, single-crystal and refractory grades, combining alumina-like hardness with good chemical and thermal shock resistance.
Reference datasheet — Spinel is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the SINT-DENSE condition
Spinel tempers and conditions
Spinel is supplied in 4 conditions, soft to hard. SINT-DENSE is the default FabDigit quotes; the values on this page are for it.
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 |
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?
Spinel (MgAl2O4) is a cubic magnesium aluminate ceramic supplied as dense sintered, transparent HIP'd, single-crystal and refractory grades, combining alumina-like hardness with good chemical and thermal shock resistance. It is chosen for optical windows and domes and for refractory linings, in plate, dome, tube and block form, with a density of 3.55 g/cm³, elastic modulus of 265 GPa, thermal conductivity of 15 W/m·K and service to 1600 °C. Its cubic structure makes transparent grades optically isotropic, unlike sapphire. Fired parts can only be diamond-ground, and transparent grades require vacuum sintering plus HIP, which drives cost and lead time. Spinel has a density of 3.55 g/cm³ (0.128 lb/in³), lighter than 66% of ceramic grades. It melts at 2,135°C (3,875 °F). Spinel has a tensile strength of 120 MPa (17.4 ksi), stronger than 51% of ceramic grades. The elastic modulus is 265 GPa (38.4 Msi).
What is Spinel used for?
- transparent armor/windows
- refractory linings
- IR domes
- molten metal handling refractories
Advantages
- Good corrosion resistance — 92/100, better than 88% of ceramic grades
- High service temperature — 1,600°C (2,912 °F), better than 86% of ceramic grades
Spinel properties
Typical room-temperature values for Spinel-SINT-DENSE; bars are the position among ceramic grades.
Physical5
Spinel has a density of 3.55 g/cm³ (0.128 lb/in³), lighter than 66% of ceramic grades. It melts at 2,135°C (3,875 °F).
Mechanical11
Spinel has a tensile strength of 120 MPa (17.4 ksi), stronger than 51% of ceramic grades. The elastic modulus is 265 GPa (38.4 Msi).
Thermal5
Spinel is rated for continuous service to 1,600°C (2,912 °F). It conducts heat at 15 W/m·K (8.67 BTU/hr·ft·°F), worse than 57% of ceramic grades. Thermal expansion is 6 µm/m·K (3.33 µin/in·°F).
Electrical5
Spinel 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 (92/100), better than 88% of ceramic grades.
Sustainability4
Producing a kilogram of Spinel 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's machinability is not recommended (5/100, worse than 59% of ceramic grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the ceramic family
Yield strength against density for every ceramic grade FabDigit runs. Spinel is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Spinel
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.
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) | — |
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.
Equivalent designations
Standards and trade names that resolve to Spinel in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- MgAl2O4
How much does Spinel cost?
Spinel is a high-cost ceramic ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Spinel — frequently asked
What is Spinel used for?
Spinel is typically used for transparent armor/windows, refractory linings, IR domes and molten metal handling refractories. In short: transparent structural ceramic; optically isotropic cubic oxide; good thermal shock resistance.
What is the tensile strength of Spinel?
Spinel has a typical tensile strength of 120 MPa (17.4 ksi) — stronger than 51% of ceramic grades. Strength varies by condition: see the 4 listed tempers.
Is Spinel easy to machine?
Not especially — machinability is rated not recommended (5/100, worse than 59% of ceramic grades). Green machining before firing is the economical route; fired parts require diamond grinding, lapping and ultrasonic/laser drilling with light passes to avoid subsurface damage.
Can Spinel be welded?
Not weldable — join by active-metal brazing (Ti/Ag-Cu), glass frit sealing or metallised Mo-Mn plus Ni plating for vacuum-tight assemblies.
What surface finishes work on Spinel?
Diamond lapping then colloidal-silica or CeO2 polishing gives optical λ/10 flatness and <1 nm Ra; AR coatings are applied for IR window use, and no anodising/plating is applicable.
Can Spinel be formed, bent or molded?
Uniaxial/isostatic pressing, slip or tape casting and injection moulding of fine MgAl2O4 powder; transparent grades need vacuum sintering or hot pressing followed by HIP at 1750–1900 °C / 150–200 MPa; allow ~15–18 % firing shrinkage.
What is the maximum service temperature of Spinel?
Spinel is rated for continuous use to about 1,600°C (2,912 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Spinel cost?
Spinel is a high-cost ceramic ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.