Quartz Glass Technical Specifications
Quick Answer: FGQuartz high-purity fused silica (SiO₂ ≥ 99.99%) supports continuous service to 1200°C (short-term 1300°C), has near-zero thermal expansion (5.5 × 10⁻⁷ /°C), transmits 185–2500 nm optically, and resists all common acids except hydrofluoric acid and hot concentrated phosphoric acid. Full mechanical, thermal, electrical, optical, chemical, and acoustic data tables are below.
Key Takeaways
- Thermal: 1200°C continuous / 1300°C short-term service, softening point ≈1680°C, near-zero thermal expansion.
- Mechanical: Mohs hardness 5.5–6.5, compressive strength 1100 MPa — strong but brittle, handle accordingly.
- Electrical: Excellent insulator (>10¹⁸ Ω·cm at 20°C), low dielectric loss — suited to high-frequency and isolation applications.
- Optical: 185–2500 nm transmission range (grade-dependent), refractive index 1.4585 at 589 nm.
- Chemical: Excellent resistance to HCl, HNO₃, H₂SO₄, aqua regia, and organic solvents — but attacked by HF and hot concentrated phosphoric acid.
- vs. Alternatives: Outperforms borosilicate glass on temperature range and UV transmission; alumina ceramic tolerates higher temperatures but is opaque and not weldable.
Comprehensive material properties and performance data for our ≥99.99% high-purity quartz glass, engineered for precision and reliability across semiconductor, optical, and high-temperature industrial environments.
Material Properties Overview
The following data applies to our standard high-purity fused silica (SiO₂ ≥ 99.99%), produced from both natural fused quartz and synthetic fused silica depending on grade and application — see our JGS1/JGS2/JGS3 grade guide for how raw material source affects optical performance. Values below are typical baseline figures; final tolerances for a specific component are confirmed during engineering DFM review for your standard product or custom fabrication order.
Physical & Mechanical Properties
Relevant when specifying structural rods, tank walls, or any component under mechanical load. The low density combined with high hardness makes it ideal for precision components requiring minimal weight and maximum durability, though the material remains brittle — see handling guidance on individual product pages.
| Property | Value |
|---|---|
| Mohs Hardness | 5.5 – 6.5 |
| Compressive Strength | 1100 MPa |
| Flexural Strength (20°C) | 67 MPa |
| Tensile Strength | 48 MPa |
| Young’s Modulus (20°C) | 72 GPa |
| Shear Modulus | 31 GPa |
| Bulk Modulus | 37 GPa |
| Poisson’s Ratio | 0.17 |
| Density (20°C) | 2.2 g/cm³ |
Thermal Properties
The property set behind every furnace tube, wafer boat, and crucible on this site. Near-zero thermal expansion allows a red-hot component to be quenched without cracking — the basis of quartz’s thermal shock resistance.
| Property | Value |
|---|---|
| Annealing Point | ≈ 1215 °C |
| Strain Point | ≈ 1120 °C |
| Max. Working Temp (Continuous) | 1200 °C |
| Max. Working Temp (Short Term) | 1300 °C |
| Thermal Expansion (20-300°C) | 5.5 × 10⁻⁷ /°C |
| Thermal Conductivity (20°C) | 1.4 W/(m·K) |
| Specific Heat (20°C) | 670 J/(kg·K) |
| Thermal Diffusivity (20°C) | 9.5 × 10⁻⁷ m²/s |
| Softening Point | ≈ 1680 °C |
Electrical Properties
Excellent electrical insulation properties with high resistivity and ultra-low dielectric loss. Indispensable for high-frequency applications and electrical isolation in semiconductor processing equipment, including custom threaded standoffs and isolation elements.
| Property | Value |
|---|---|
| Resistivity (at 20°C) | > 10¹⁸ Ω·cm |
| Resistivity (at 350°C) | 7 × 10⁵ Ω·cm |
| Dielectric Constant (1 MHz, 20°C) | 3.75 |
| Dielectric Strength | 25 – 40 kV/mm |
| Dielectric Loss Factor (1 MHz) | < 1 × 10⁻⁴ |
| Dielectric Loss Factor (1 GHz) | < 6 × 10⁻⁴ |
Optical Properties
Unrivaled UV transmission and optical clarity make fused silica a staple for spectroscopy, laser optics, and deep-UV applications. Values below are for standard clear material; grade-specific transmission bands (JGS1/JGS2/JGS3) are detailed on our optical quartz glass page.
| Property | Value |
|---|---|
| Refractive Index (589 nm, 20°C) | 1.4585 |
| Refractive Index (1060 nm) | 1.4496 |
| Transmission Range | 185 – 2500 nm |
| UV Transmission (254 nm, 10mm) | > 90% |
| Abbe Number | 67.8 |
| Stress Optical Coefficient | 3.5 × 10⁻⁶ MPa⁻¹ |
Chemical Composition & Purity
Ultra-high purity with meticulously controlled metallic impurities ensures minimal contamination risk during sensitive wafer fabrication and wet processing. Material composition is verified for every production batch.
| Property | Value |
|---|---|
| SiO₂ Content | ≥ 99.99% |
| OH Content | < 10 ppm |
| Al Impurity | < 10 ppm |
| Fe Impurity | < 5 ppm |
| Na + K Impurities | < 5 ppm |
| Total Metal Impurities | < 20 ppm |
| Acid Resistance | Excellent vs. HCl, HNO₃, H₂SO₄, aqua regia, organic solvents |
| Known Limitations | Attacked by HF and hot concentrated phosphoric acid; caution with strong hot alkalis |
Additional Properties
Material characteristics covering acoustic transmission, radiation resistance, and vacuum surface integrity — relevant to specialized applications such as sensor components and vacuum chamber viewports.
| Property | Value |
|---|---|
| Acoustic Velocity (Longitudinal) | 5968 m/s |
| Acoustic Velocity (Transverse) | 3764 m/s |
| Radiation Resistance | Good |
| Permeability (He at 700°C) | Low |
| Surface Energy | ≈ 300 mJ/m² |
| Outgassing Rate (Vacuum) | Very Low |
Material Performance Comparison
Understanding how high-purity quartz glass compares to other advanced engineering materials is critical for optimal equipment design. While alternatives like borosilicate glass or alumina ceramic have their uses, fused silica remains the only material capable of simultaneously delivering ultra-high purity, deep-UV optical transmission, and extreme thermal shock resistance in one monolithic structure.
| Property | Fused Silica | Borosilicate Glass | Alumina Ceramic |
|---|---|---|---|
| Max. Continuous Temp. | 1200°C | ~500°C | ~1600°C |
| Thermal Expansion | 5.5 × 10⁻⁷ /°C | 3.3 × 10⁻⁶ /°C | 7.2 × 10⁻⁶ /°C |
| Optical Transmission | Deep UV–IR (185–2500nm) | Visible only | Opaque |
| Machinability / Weldability | CNC machinable, flame weldable | Limited | Not weldable |
Frequently Asked Questions
Hydrofluoric acid (HF) and hot concentrated phosphoric acid both attack and etch the SiO2 network. Strong hot alkaline solutions should also be used with caution. All other common acids and organic solvents are handled with excellent resistance.
Most physical, thermal, and electrical properties are consistent across natural and synthetic material. Optical transmission and trace-impurity levels vary more significantly by grade — see the JGS1/JGS2/JGS3 grade guide for optical-specific data.
These are typical baseline values for standard high-purity fused silica. Final tolerances for a specific geometry are confirmed during engineering DFM review, since factors like wall thickness, forming method, and grade selection affect actual performance.
Need Custom Specifications Evaluated?
Every geometry has different critical dimensions. Send your drawing or application details and our engineering team will confirm which of these baseline properties applies to your specific component, and flag anything that needs tighter tolerance or a different grade.