Engineers and buyers in fields such as precision optics, semiconductors, and laser systems often require materials with extremely low thermal expansion coefficients for their equipment components. Low-expansion glass can minimize thermal deformation and maintain dimensional stability. Today, I’ll compare the five most commonly used low-expansion materials—Zerodur, ULE, ClearCeram (glass-ceramic), BF33 (Borofloat 33), and Fused Silica—to help you better select the material that best suits your needs.
Material Profiles
Microcrystalline glass-ceramic, available in a variety of customizable thermal expansion grades (click here to view detailed grades). It offers excellent dimensional stability and is suitable for high-precision machining.
Why choose it: Best for large optics and applications requiring sub-micron stability over time and temperature cycles.
Fused silica variant with engineered composition to reach near-zero CTE.
Why choose it: Superior for ultra-stable optical cavities and laser reference structures.
Controlled crystallization reduces CTE while improving toughness.
Why choose it: Balance of low expansion, impact resistance, and machinability; good for medium-precision optical assemblies.
Borosilicate glass with moderate low CTE, excellent chemical resistance, and high transmission through visible wavelengths.
Why choose it: Cost-effective for semiconductor process windows, inspection ports, and lab equipment where ultra-low drift is not mandatory.
High-purity silicon dioxide glass with extremely low thermal expansion and excellent optical transmission from deep UV to NIR.
Why choose it: Ideal when low thermal drift, UV compatibility, and high laser-damage threshold are required. Often preferred for precision photonics, laser systems, and demanding semiconductor windows.
CTE Comparison Table
| 素材 | Typical CTE (α, ×10⁻⁶ /K) |
| Zerodur | ~0 ±0.02 |
| ユーリー | ~0 ±0.03 |
| ClearCeram | ~0 ±0.1 |
| BF33 | ≈3.3 |
| 溶融シリカ | ≈0.5 |
Practical selection guide
Need absolute long-term dimensional stability (nm-scale)? → ULE / Zerodur.
Require low CTE + better mechanical toughness? → ClearCeram / Zerodur
Need optical window with chemical resistance and moderate thermal performance? → BF33.
Need low CTE, UV transmission, or high laser-damage threshold? → 溶融シリカ.
On a strict budget for non-critical thermal environments? → Evaluate BF33 or lower-cost substrates depending on optical requirements.
Low thermal expansion glass machining
Jundro has extensive expertise in machining ultra-hard materials, with rich experience in producing complex geometries, including curved surfaces, intricate shapes, honeycomb, and lightweight structures. Our optical components achieve a flatness accuracy of up to 1/20λ, and we can also provide optical coating services. If you have any material machining needs, please feel free to contact us.
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