Ge PC-OPT
Grade
PC-OPT = polycrystalline optical germanium
Lower-cost, large-diameter windows and non-diamond-turned optics where grain boundaries in the surface are acceptable.
Values for the PC-OPT condition
Other Ge tempers and conditions
Ge is listed in 5 conditions; see the grade overview at Ge.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SC-OPTDefault Optical-grade single crystal | Standard choice for thermal-imaging lenses, windows and domes needing best 8–12 µm transmission and diamond-turnable surfaces. | — | 70 | 0 | 800 HV | 59 W/m·K |
High-resistivity / near-intrinsic single crystal | Pick when minimum free-carrier absorption is critical — long path lengths, THz components, CO2-laser and high-power IR optics. | — | 70 | 0 | 800 HV | 60 W/m·K |
Semiconductor/substrate-grade single crystal | Ga- or Sb-doped <100>/<111> wafers for III–V epitaxy and multi-junction solar cells, not for IR imaging optics. | — | 70 | 0 | 800 HV | 55 W/m·K |
Single crystal with AR / diamond-like-carbon coating | Use for any real system: multilayer AR (and DLC on the outer face) removes the 36 %/surface reflection and adds rain/sand erosion resistance. | — | 70 | 0 | 1,800 HV | 59 W/m·K |
PC-OPTThis page Polycrystalline optical germanium | Lower-cost, large-diameter windows and non-diamond-turned optics where grain boundaries in the surface are acceptable. | — | 75 | 0 | 790 HV | 57 W/m·K |
What is Ge PC-OPT?
Ge PC-OPT is Ge in the PC-OPT grade — lower-cost, large-diameter windows and non-diamond-turned optics where grain boundaries in the surface are acceptable. Ge PC-OPT has a tensile strength of 75 MPa (10.9 ksi), stronger than 79% of glass grades. Elongation at break is 0% and the elastic modulus is 103 GPa (14.9 Msi). Ge PC-OPT has a density of 5.32 g/cm³ (0.192 lb/in³), heavier than 93% of glass grades. It melts at 938°C (1,720 °F). SC-OPT is the default condition FabDigit quotes; PC-OPT is available on request or by drawing note.
Advantages
- Conducts heat well — 57 W/m·K (32.9 BTU/hr·ft·°F), better than 95% of glass grades
- Stiff — 103 GPa (14.9 Msi), better than 81% of glass grades
- Easy to machine — 40/100, better than 80% of glass grades
Limitations
- Limited service temperature — 100°C (212 °F), worse than 98% of glass grades
- High embodied carbon — 130 kg CO₂/kg, worse than 97% of glass grades
- Heavy — 5.32 g/cm³ (0.192 lb/in³), worse than 93% of glass grades
Ge PC-OPT properties
Typical room-temperature values for Ge PC-OPT; 16 are specific to this condition. Other listed values are Ge reference data and may not represent this condition. Bars are the position among glass grades.
Physical4
Ge PC-OPT has a density of 5.32 g/cm³ (0.192 lb/in³), heavier than 93% of glass grades. It melts at 938°C (1,720 °F).
Mechanical13
Ge PC-OPT has a tensile strength of 75 MPa (10.9 ksi), stronger than 79% of glass grades. Elongation at break is 0% and the elastic modulus is 103 GPa (14.9 Msi).
Thermal5
Ge PC-OPT is rated for continuous service to 100°C (212 °F). It conducts heat at 57 W/m·K (32.9 BTU/hr·ft·°F), better than 95% of glass grades. Thermal expansion is 5.9 µm/m·K (3.28 µin/in·°F).
Electrical3
Ge PC-OPT has an electrical resistivity of 0.3 Ω·m.
Chemical & Environmental2
Corrosion resistance is good (55/100), worse than 74% of glass grades.
Sustainability3
Producing a kilogram of Ge PC-OPT takes about 2,000 MJ of energy and emits 130 kg of CO₂ — more than 97% of glass grades. Typical recycled content is 30%.
Manufacturability2
Ge PC-OPT's machinability is fair (40/100, better than 80% of glass grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Ge PC-OPT
Is Ge easy to machine?
Grind and lap with diamond abrasives, then single-point diamond turn with light depths of cut and copious coolant; it is brittle with {111} cleavage, so edges must be chamfered and clamping loads kept low.
Can Ge be welded?
Not weldable — mount by elastomeric bonding, low-stress epoxy or spring/retainer rings that accommodate its 5.9 µm/m·K CTE.
Can Ge be formed, bent or molded?
Shaped only by crystal growth (Czochralski/casting) plus subtractive optical finishing; no plastic forming at room temperature.
What surface finishes work on Ge?
Polishes to sub-nanometre roughness; virtually always finished with multilayer 8–12 µm AR coatings and a DLC or hard-carbon layer on exposed outer surfaces.
Ge 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.
| Element | Spec limit (wt %) |
|---|---|
| Sbppb-level n-type dopant deliberately added in some crystals to set resistivity | ≈ 0 |
| Gezone-refined 5N–6N feedstock; optical grade specified by resistivity (5–40 Ω·cm) and dislocation/etch-pit density rather than by trace chemistry | ≥ 100 (balance) |
Ge PC-OPT — frequently asked
What is Ge PC-OPT used for?
Ge PC-OPT is typically used for thermal imaging lenses, IR windows, AR-coated Ge optics and laser optics. In short: standard 8–12 µm lens material; high index, high density; limited to ~100 °C service.
What is the tensile strength of Ge PC-OPT?
Ge PC-OPT has a typical tensile strength of 75 MPa (10.9 ksi) — stronger than 79% of glass grades. Strength varies by condition: see the 5 listed tempers.
Is Ge PC-OPT easy to machine?
Not especially — machinability is rated fair (40/100, better than 80% of glass grades). Grind and lap with diamond abrasives, then single-point diamond turn with light depths of cut and copious coolant; it is brittle with {111} cleavage, so edges must be chamfered and clamping loads kept low.
Can Ge PC-OPT be welded?
Not weldable — mount by elastomeric bonding, low-stress epoxy or spring/retainer rings that accommodate its 5.9 µm/m·K CTE.
What surface finishes work on Ge PC-OPT?
Polishes to sub-nanometre roughness; virtually always finished with multilayer 8–12 µm AR coatings and a DLC or hard-carbon layer on exposed outer surfaces.
Can Ge PC-OPT be formed, bent or molded?
Shaped only by crystal growth (Czochralski/casting) plus subtractive optical finishing; no plastic forming at room temperature.
What is the maximum service temperature of Ge PC-OPT?
Ge PC-OPT 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
- ASM Handbook Vol. 2 — Properties of Nonferrous Alloys and Special-Purpose Materials (germanium) — ASM International (1990)
- Handbook of Optical Constants of Solids — Academic Press (1998)
- CRC Handbook of Chemistry and Physics, 97th ed. — CRC Press (2016)
- Germanium (Ge) IR optical material datasheet — II-VI / Coherent, Umicore, Crystran (2023)
- Landolt-Börnstein: Semiconductors — Group IV Elements, elastic constants of Ge — Springer (2001)
- Mineral Commodity Summaries — Germanium (recycling and price) — USGS (2025)
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.