KRS-5
KRS-5 is a mixed thallium bromide/iodide single crystal, also supplied as hot-extruded polycrystalline rod and IR fibre.
Reference datasheet — KRS-5 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 SC-OPT condition
KRS-5 tempers and conditions
KRS-5 is supplied in 2 conditions, soft to hard. SC-OPT is the default FabDigit quotes; the values on this page are for it.
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SC-OPTDefault Bridgman-grown single crystal, optical window grade | Choose the Bridgman-grown single crystal for infrared windows, lenses and spectroscopic windows where the highest transmission and scatter-free optics are required. | 26 | 2 | 40 HV | 0.54 W/m·K | |
hot-extruded polycrystalline (IR fibre / light-guide stock) | Use the hot-extruded fine-grained polycrystal for flexible infrared transmitting fibre and high aspect-ratio light guides; strength beats single crystal but grain-boundary scatter lowers transmission. | 35 | 3 | 45 HV | 0.5 W/m·K |
Supply forms, finishes and certifications
Ways KRS-5 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
ATR | Oriented and polished ATR prism / IRE grade | Surface finish |
What is KRS-5?
KRS-5 is a mixed thallium bromide/iodide single crystal, also supplied as hot-extruded polycrystalline rod and IR fibre. It transmits 0.6–40 µm — the widest span of the common IR materials — and is insoluble in water, so it is used for ATR prisms working against aqueous samples where alkali halides dissolve. It is soft and ductile (machinability score 55), cold-flows under clamping load, and the thallium content is toxic, so all swarf and dust must be contained. Its index near 2.37 costs about 30 % Fresnel reflection, so AR coating is normal; ZnSe is the harder, non-toxic choice when coverage to 22 µm is enough. KRS-5 has a density of 7.37 g/cm³ (0.266 lb/in³), heavier than 100% of glass grades. It melts at 415°C (778 °F). KRS-5 has a tensile strength of 26 MPa (3.77 ksi), weaker than 86% of glass grades. Elongation at break is 2% and the elastic modulus is 15.9 GPa (2.31 Msi).
What is KRS-5 used for?
- ATR spectroscopy prisms
- IR fiber optics
- IR windows
Advantages
- Easy to machine — 55/100, better than 93% of glass grades
- Ductile — tolerates forming and impact — 2%, better than 84% of glass grades
Limitations
- Heavy — 7.37 g/cm³ (0.266 lb/in³), worse than 100% of glass grades
- Hard to polish — 35/100, worse than 100% of glass grades
- Poor heat conductor — 0.54 W/m·K (0.312 BTU/hr·ft·°F), worse than 98% of glass grades
- Low stiffness — 15.9 GPa (2.31 Msi), worse than 97% of glass grades
- Limited service temperature — 150°C (302 °F), worse than 92% of glass grades
KRS-5 properties
Typical room-temperature values for KRS-5-SC-OPT; bars are the position among glass grades.
Physical5
KRS-5 has a density of 7.37 g/cm³ (0.266 lb/in³), heavier than 100% of glass grades. It melts at 415°C (778 °F).
Mechanical13
KRS-5 has a tensile strength of 26 MPa (3.77 ksi), weaker than 86% of glass grades. Elongation at break is 2% and the elastic modulus is 15.9 GPa (2.31 Msi).
Thermal4
KRS-5 is rated for continuous service to 150°C (302 °F). It conducts heat at 0.54 W/m·K (0.312 BTU/hr·ft·°F), worse than 98% of glass grades. Thermal expansion is 58 µm/m·K (32.2 µin/in·°F).
Electrical2
KRS-5 has an electrical resistivity of 1×10⁸ Ω·m.
Chemical & Environmental2
Corrosion resistance is good (55/100), worse than 74% of glass grades.
Manufacturability2
KRS-5's machinability is good (55/100, better than 93% of glass 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 glass family
Yield strength against density for every glass grade FabDigit runs. KRS-5 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with KRS-5
Is KRS-5 easy to machine?
Very soft and highly plastic: single-point diamond turn or cut with a fine-grit wire saw, keeping cutting forces very low so the material does not cold-flow. Run dry or with kerosene lubrication, and enclose the operation with sealed extraction because the debris contains thallium.
Can KRS-5 be welded?
Not weldable — an ionic crystal. Assemble by mechanical clamping or low-stress optical adhesive, and avoid direct contact with silver, copper or nickel.
Can KRS-5 be formed, bent or molded?
Hot extruded or hot forged at roughly 250–350 °C into polycrystalline rod or IR fibre. Single crystals are grown by the Bridgman–Stockbarger method and must be cooled slowly to avoid residual stress and slip bands.
KRS-5 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 |
|---|---|---|
| Tlas TlBr 42 mol% + TlI 58 mol% solid solution | 64.5 – 66.5 | 65.6 |
| ITlI about 61.7 wt% | 22.5 – 24.5 | 23.6 |
| BrTlBr about 38.3 wt% | 10 – 11.5 | 10.8 |
| (metallic impurities)total metal impurities, optical grade | ≤ 0.01 | 0.01 |
What surface finishes work on KRS-5?
Polish at light pressure with soft felt and fine alumina or diamond in anhydrous (alcohol) media; the surface scratches very easily. AR stacks such as ZnSe/BaF2 are applied to offset the ~30 % reflection loss from n≈2.37, and clamping faces must be supported to prevent plastic deformation.
Equivalent designations
Standards and trade names that resolve to KRS-5 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- TlBr-TlI
How much does KRS-5 cost?
KRS-5 is a high-cost glass ($$$$), 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.
KRS-5 — frequently asked
What is KRS-5 used for?
KRS-5 is typically used for ATR spectroscopy prisms, IR fiber optics and IR windows. In short: widest IR range, to 40 µm; water-insoluble ATR crystal; soft, ductile, thallium-toxic.
What is the tensile strength of KRS-5?
KRS-5 has a typical tensile strength of 26 MPa (3.77 ksi) — weaker than 86% of glass grades. Strength varies by condition: see the 2 listed tempers.
Is KRS-5 easy to machine?
Reasonably — machinability is rated good (55/100, better than 93% of glass grades). Very soft and highly plastic: single-point diamond turn or cut with a fine-grit wire saw, keeping cutting forces very low so the material does not cold-flow. Run dry or with kerosene lubrication, and enclose the operation with sealed extraction because the debris contains thallium.
Can KRS-5 be welded?
Not weldable — an ionic crystal. Assemble by mechanical clamping or low-stress optical adhesive, and avoid direct contact with silver, copper or nickel.
What surface finishes work on KRS-5?
Polish at light pressure with soft felt and fine alumina or diamond in anhydrous (alcohol) media; the surface scratches very easily. AR stacks such as ZnSe/BaF2 are applied to offset the ~30 % reflection loss from n≈2.37, and clamping faces must be supported to prevent plastic deformation.
Can KRS-5 be formed, bent or molded?
Hot extruded or hot forged at roughly 250–350 °C into polycrystalline rod or IR fibre. Single crystals are grown by the Bridgman–Stockbarger method and must be cooled slowly to avoid residual stress and slip bands.
What is the maximum service temperature of KRS-5?
KRS-5 is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does KRS-5 cost?
KRS-5 is a high-cost glass ($$$$), 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
- KRS-5 (Thallium Bromo-Iodide) Optical Material Data — Crystran Ltd. (2023)
- KRS-5 Crystal Properties — Korth Kristalle GmbH (2022)
- Handbook of Optical Constants of Solids — Academic Press (Palik ed.) (1998)
- Handbook of Optical Materials — CRC Press (Weber) (2003)
- KRS-5 ATR Crystals and IR Windows — ISP Optics / Crystaltechno (2022)
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.