IRG 24 CHG (Chalcogenide As₄₀Se₆₀ glass)
Grade · default condition
also Schott IRG 24
Pick for 3–5 µm and 8–12 µm thermal imaging optics that must be diamond-turned or precision-moulded at low temperature.
Values for the CHG condition
Other IRG 24 tempers and conditions
IRG 24 is listed in 2 conditions; see the grade overview at IRG 24.
- CHG
- GEO
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
CHGDefaultThis page Chalcogenide As₄₀Se₆₀ glass | Pick for 3–5 µm and 8–12 µm thermal imaging optics that must be diamond-turned or precision-moulded at low temperature. | — | 16 | 0 | 110 HV | 0.2 W/m·K |
Germanate (GeO₂-based) IR transmitting glass | Pick when visible-to-~5 µm transmission plus hard, polishable, high-temperature-capable oxide glass is needed (windows, domes, MWIR lenses). | — | 45 | 0 | 460 HV | 0.9 W/m·K |
What is IRG 24 CHG?
IRG 24 CHG is IRG 24 in the CHG grade — pick for 3–5 µm and 8–12 µm thermal imaging optics that must be diamond-turned or precision-moulded at low temperature. IRG 24 CHG has a tensile strength of 16 MPa (2.32 ksi), weaker than 91% of glass grades. Elongation at break is 0% and the elastic modulus is 18.3 GPa (2.65 Msi). IRG 24 CHG has a density of 4.64 g/cm³ (0.168 lb/in³), heavier than 81% of glass grades.
Advantages
- Easy to machine — 85/100, better than 100% of glass grades
Limitations
- Poor heat conductor — 0.2 W/m·K (0.116 BTU/hr·ft·°F), worse than 100% of glass grades
- Low stiffness — 18.3 GPa (2.65 Msi), worse than 95% of glass grades
- Low fracture toughness — 0.17 MPa·√m (0.155 ksi·√in), worse than 93% of glass grades
- Limited service temperature — 120°C (248 °F), worse than 93% of glass grades
- Heavy — 4.64 g/cm³ (0.168 lb/in³), worse than 81% of glass grades
IRG 24 CHG properties
Typical room-temperature values for IRG 24 CHG; 17 are specific to this condition. Other listed values are IRG 24 reference data and may not represent this condition. Bars are the position among glass grades.
Physical4
IRG 24 CHG has a density of 4.64 g/cm³ (0.168 lb/in³), heavier than 81% of glass grades.
Mechanical12
IRG 24 CHG has a tensile strength of 16 MPa (2.32 ksi), weaker than 91% of glass grades. Elongation at break is 0% and the elastic modulus is 18.3 GPa (2.65 Msi).
Thermal5
IRG 24 CHG is rated for continuous service to 120°C (248 °F). It conducts heat at 0.2 W/m·K (0.116 BTU/hr·ft·°F), worse than 100% of glass grades. Thermal expansion is 20.7 µm/m·K (11.5 µin/in·°F).
Electrical3
IRG 24 CHG has an electrical resistivity of 1×10¹¹ Ω·m.
Chemical & Environmental2
Corrosion resistance is good (55/100), worse than 74% of glass grades.
Manufacturability2
IRG 24 CHG's machinability is excellent (85/100, better than 100% of glass grades).
Common Calculations4
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with IRG 24 CHG
Is IRG 24 easy to machine?
Excellent single-point diamond turning (low Tg, no crystalline structure); grind/polish with light pressure and non-alkaline slurries to avoid surface staining.
Can IRG 24 be welded?
Not weldable; parts are joined by optical contacting, epoxy bonding or metal-mount cementing, and glass is fused only during melt/casting under vacuum.
Can IRG 24 be formed, bent or molded?
Precision glass moulding near Tg ≈ 185 °C in inert atmosphere gives aspheres and diffractive surfaces without post-polishing; anneal slowly to avoid stress birefringence.
What surface finishes work on IRG 24?
Always AR-coat (DLC or ZnS/YF₃ stacks) — the bare surface is soft, scratch-prone and slowly tarnishes in humid air.
IRG 24 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 |
|---|---|---|
| Se≈60 at% Se (As₄₀Se₆₀ base glass) | 58 – 63 | 61.3 |
| As≈40 at% As; melted in sealed silica ampoule from 5N-6N elements | ≥ 37 (balance) | — |
IRG 24 CHG — frequently asked
What is IRG 24 CHG used for?
IRG 24 CHG is typically used for thermal imaging lenses, IR sensor windows, night-vision optics and laser rangefinder optics. In short: diamond-turnable IR glass; mouldable near 185 °C; near/mid-IR transmission.
What is the tensile strength of IRG 24 CHG?
IRG 24 CHG has a typical tensile strength of 16 MPa (2.32 ksi) — weaker than 91% of glass grades. Strength varies by condition: see the 2 listed tempers.
Is IRG 24 CHG easy to machine?
Yes — machinability is rated excellent (85/100, better than 100% of glass grades). Excellent single-point diamond turning (low Tg, no crystalline structure); grind/polish with light pressure and non-alkaline slurries to avoid surface staining.
Can IRG 24 CHG be welded?
Not weldable; parts are joined by optical contacting, epoxy bonding or metal-mount cementing, and glass is fused only during melt/casting under vacuum.
What surface finishes work on IRG 24 CHG?
Always AR-coat (DLC or ZnS/YF₃ stacks) — the bare surface is soft, scratch-prone and slowly tarnishes in humid air.
Can IRG 24 CHG be formed, bent or molded?
Precision glass moulding near Tg ≈ 185 °C in inert atmosphere gives aspheres and diffractive surfaces without post-polishing; anneal slowly to avoid stress birefringence.
What is the maximum service temperature of IRG 24 CHG?
IRG 24 CHG is rated for continuous use to about 120°C (248 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Infrared Chalcogenide Glasses IRG 22–IRG 27 — SCHOTT AG (2023)
- Infrared Transmitting Glasses IRG 2 / IRG 11 (germanate and calcium-aluminate types) — SCHOTT AG (2022)
- AMTIR-2 (As₄₀Se₆₀) optical and mechanical data — Amorphous Materials Inc. (2021)
- Handbook of Optics, Vol. IV — Properties of Infrared Optical Materials — OSA/McGraw-Hill (2010)
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.