CsI TL (CsI:Tl)
Additive grade
Pick the thallium-doped scintillator for gamma spectrometry, security screening and nuclear medicine: about 54000 photons/MeV with 550 nm emission matched to photodiodes and SiPMs.
Values for the TL condition
Other CsI tempers and conditions
CsI is listed in 5 conditions; see the grade overview at CsI.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Columnar vapor-deposited CsI:Tl scintillator film | Pick the vacuum-deposited columnar Tl-doped film, 150–800 µm thick, when light piping in the needle structure must raise spatial resolution in flat-panel X-ray detectors and image intensifiers. | — | 1 | 0.5 | 12 HV | 0.4 W/m·K |
IRDefault Undoped optical-grade single crystal | Choose the undoped optical-grade single crystal for 0.25–55 µm FTIR windows, prisms and far-infrared optics that demand the highest transmission and lowest scatter. | — | 5 | 2 | 20 HV | 1 W/m·K |
TLThis page CsI:Tl | Pick the thallium-doped scintillator for gamma spectrometry, security screening and nuclear medicine: about 54000 photons/MeV with 550 nm emission matched to photodiodes and SiPMs. | — | 5 | 2 | 20 HV | 1 W/m·K |
CsI:Na | Use the sodium-doped crystal as a shock-resistant NaI(Tl) substitute: 420 nm emission matches bialkali photomultipliers at roughly 40000 photons/MeV light output. | — | 5 | 2 | 20 HV | 1 W/m·K |
Hot-forged / hot-pressed polycrystalline CsI | Choose the hot-forged fine-grained polycrystal for large-aperture infrared windows and domes, gaining strength and cleavage resistance over single crystal at some optical cost. | — | 10 | 1.5 | 25 HV | 1 W/m·K |
What is CsI TL?
CsI TL is CsI in the TL grade — pick the thallium-doped scintillator for gamma spectrometry, security screening and nuclear medicine: about 54000 photons/MeV with 550 nm emission matched to photodiodes and SiPMs. CsI TL has a tensile strength of 5 MPa (0.725 ksi), weaker than 96% of glass grades. Elongation at break is 2% and the elastic modulus is 5.3 GPa (0.769 Msi). CsI TL has a density of 4.51 g/cm³ (0.163 lb/in³), heavier than 78% of glass grades. It melts at 621°C (1,150 °F). IR is the default condition FabDigit quotes; TL is available on request or by drawing note.
Advantages
- Easy to machine — 45/100, better than 85% of glass grades
- Ductile — tolerates forming and impact — 2%, better than 84% of glass grades
Limitations
- Low stiffness — 5.3 GPa (0.769 Msi), worse than 100% of glass grades
- Limited service temperature — 100°C (212 °F), worse than 98% of glass grades
- Low fracture toughness — 0.15 MPa·√m (0.137 ksi·√in), worse than 97% of glass grades
- Hard to polish — 40/100, worse than 97% of glass grades
- Needs corrosion protection — 12/100, worse than 92% of glass grades
CsI TL properties
Typical room-temperature values for CsI TL; 18 are specific to this condition. Other listed values are CsI reference data and may not represent this condition. Bars are the position among glass grades.
Physical5
CsI TL has a density of 4.51 g/cm³ (0.163 lb/in³), heavier than 78% of glass grades. It melts at 621°C (1,150 °F).
Mechanical12
CsI TL has a tensile strength of 5 MPa (0.725 ksi), weaker than 96% of glass grades. Elongation at break is 2% and the elastic modulus is 5.3 GPa (0.769 Msi).
Thermal5
CsI TL is rated for continuous service to 100°C (212 °F). It conducts heat at 1.1 W/m·K (0.636 BTU/hr·ft·°F), worse than 68% of glass grades. Thermal expansion is 54 µm/m·K (30 µin/in·°F).
Electrical3
CsI TL has an electrical resistivity of 1×10⁹ Ω·m.
Chemical & Environmental2
Corrosion resistance is not recommended (12/100), worse than 92% of glass grades.
Manufacturability2
CsI TL's machinability is fair (45/100, better than 85% of glass grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with CsI TL
Is CsI easy to machine?
Very soft and highly ductile: cut dry or with anhydrous kerosene or mineral oil, where diamond turning and diamond cutting wheels both work well. Excessive clamping force causes permanent deformation, and water-based coolant is prohibited.
Can CsI be welded?
Not applicable — crystal material is not welded. Seal into metal mounts with low-stress elastic adhesive or indium gaskets.
Can CsI be formed, bent or molded?
Single crystals are grown by the crucible-descent (Bridgman) or Czochralski method, and fine-grained polycrystalline windows can be hot forged at roughly 400–500 °C. Scintillator screens are vacuum-evaporated to build the columnar structure.
What surface finishes work on CsI?
Polish anhydrously with ethylene glycol or anhydrous alcohol plus fine powder, then dry and seal the part immediately. ZnS/DLC or parylene moisture barriers can be applied; adhesion of conventional AR coatings is limited.
CsI 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 |
|---|---|---|
| Csstoichiometric CsI | 50.9 – 51.4 | 51.15 |
| TlCsI:Tl variant only, about 0.03-0.1 mol% | 0.02 – 0.1 | 0.05 |
| NaCsI:Na variant only | 0.01 – 0.1 | 0.03 |
| Inominal 48.85 wt% | balance | — |
CsI TL — frequently asked
What is CsI TL used for?
CsI TL is typically used for far-IR windows/prisms, scintillation detectors and FTIR beamsplitter substrates. In short: widest IR range halide; dual optic and scintillator; softest common IR crystal.
What is the tensile strength of CsI TL?
CsI TL has a typical tensile strength of 5 MPa (0.725 ksi) — weaker than 96% of glass grades. Strength varies by condition: see the 5 listed tempers.
Is CsI TL easy to machine?
Reasonably — machinability is rated fair (45/100, better than 85% of glass grades). Very soft and highly ductile: cut dry or with anhydrous kerosene or mineral oil, where diamond turning and diamond cutting wheels both work well. Excessive clamping force causes permanent deformation, and water-based coolant is prohibited.
Can CsI TL be welded?
Not applicable — crystal material is not welded. Seal into metal mounts with low-stress elastic adhesive or indium gaskets.
What surface finishes work on CsI TL?
Polish anhydrously with ethylene glycol or anhydrous alcohol plus fine powder, then dry and seal the part immediately. ZnS/DLC or parylene moisture barriers can be applied; adhesion of conventional AR coatings is limited.
Can CsI TL be formed, bent or molded?
Single crystals are grown by the crucible-descent (Bridgman) or Czochralski method, and fine-grained polycrystalline windows can be hot forged at roughly 400–500 °C. Scintillator screens are vacuum-evaporated to build the columnar structure.
What is the maximum service temperature of CsI TL?
CsI TL is rated for continuous use to about 100°C (212 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Caesium Iodide (CsI) optical material datasheet — Crystran Ltd (2023)
- CsI(Tl) and CsI(Na) scintillation crystal data sheets — Saint-Gobain Crystals / Luxium (2021)
- CsI single crystal specification — Korth Kristalle GmbH (2022)
- Handbook of Optical Constants of Solids (alkali halides) — Academic Press (Palik ed.) (1998)
- CRC Handbook of Chemistry and Physics, 100th ed. — CRC Press (2019)
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.