ZERODUR®
Thermal expansion
CTE tolerances of ZERODUR®
By default, the mean coefficient of thermal expansion (CTE) of ZERODUR® is measured within the temperature range of 0°C to 50°C. Five expansion classes are differentiated as follows:
CTE Grades | CTE (0°C; 50°C)* |
---|---|
ZERODUR® Expansion Class 2 | 0 ± 0.100 ・ 10-6/K |
ZERODUR® Expansion Class 1 | 0 ± 0.050 ・ 10-6/K |
ZERODUR® Expansion Class 0 | 0 ± 0.020 ・ 10-6/K |
ZERODUR® Expansion Class 0 SPECIAL | 0 ± 0.010 ・ 10-6/K |
ZERODUR® Expansion Class 0 EXTREME | 0 ± 0.007 ・ 10-6/K |
ZERODUR® TAILORED |
TAILORED ± 0.020・10-6/K |
Maximum application temperature 600°C.
Upon request, ZERODUR® is available for customized temperature ranges.
We offer expansion class 0 or better optimized for your individual application.
CTE homogeneity
Homogeneity is evaluated by measuring CTE samples homogeneously distributed throughout the blank and calculating the difference in CTE between the highest and the lowest value measured.
The homogeneity of linear expansion can be guaranteed in the following weight classes:
CTE (0°C; 50°C) Homogeneity Tolerances |
|
---|---|
up to 18 tons |
< 0.03 ・ 10-6/K |
up to 6 tons |
< 0.02 ・ 10-6/K |
up to 0.3 tons | < 0.01 ・ 10-6/K |
CTE distribution within a 1.5 m diameter blank with a measured CTE homogeneity of 0.004 · 10-6/K
CTE tolerances of ZERODUR® K20
ZERODUR® K20, a high-temperature version of ZERODUR®, has been optimized to withstand higher application temperatures.
Mean coefficient of linear thermal expansion of ZERODUR®K20 |
|
---|---|
CTE (20°C; 700°C) |
2.4 ・ 10-6/K |
CTE (20°C; 300°C) |
2.2 ・ 10-6/K |
CTE (0°C; 50°C) | 1.6 ・ 10-6/K |
Maximum application temperature 850°C.
Internal quality
If no quality is specified upon receipt of an order, then ZERODUR® will be supplied in standard quality. Individual specifications for internal quality can be fulfilled upon request.
Inclusions
Although the defect level is low, the main inclusions found in ZERODUR® are bubbles. During inspection of ZERODUR® parts, all inclusions with a diameter > 0.3 mm are taken into consideration. If an inclusion has a shape other than spherical, the average diameter is reported as the mean of the length and width. ZERODUR® is available in six different inclusion quality levels, which are defined according to the dimension of your part.
Quality levels for inclusions in ZERODUR®
Average number of inclusions per 100 cm3:
Standard | 5.0 |
---|---|
Class 4 | 5.0 |
Class 3 | 4.0 |
Class 2 | 3.0 |
Class 1 |
2.0 |
Class 0 |
1.0 |
Maximum diameter of individual inclusions in mm for different diameters or diagonals of the ZERODUR® part:
In the critical volume | < 500 mm | < 2000 mm | < 4000 mm |
---|---|---|---|
Standard | 1.4 | 2.0 | 3.0 |
Class 4 | 1.2 | 1.8 | 2.5 |
Class 3 | 1.0 | 1.6 | 2.0 |
Class 2 | 0.8 | 1.5 | 1.8 |
Class 1 | 0.6 | 1.2 | 1.6 |
Class 0 | 0.4 | 1.0 | 1.5 |
In the uncritical volume |
< 500 mm | < 2000 mm | < 4000 mm |
---|---|---|---|
Standard | 3.0 | 6.0 | 10.0 |
Class 4 | 2.0 | 5.0 | 8.0 |
Class 3 | 1.5 | 4.0 | 6.0 |
Class 2 | 1.0 | 3.0 | 6.0 |
Class 1 | 0.8 | 3.0 | 6.0 |
Class 0 | 0.6 | 3.0 | 6.0 |
Individual specifications upon request.
Bulk stress
The bulk stress birefringence of ZERODUR® is recorded in path difference per thickness in inspection direction. For discs it is measured in axial direction at 5 % of the diameter from the edge. For rectangular plates, the measurement is performed in the middle of the longer side perpendicular to the plate‘s surface.
Quality levels for bulk stress in ZERODUR®
Bulk stress birefringence [nm/cm] for parts with diameters or diagonals:
< 500 mm | < 2000 mm | < 4000 mm | |
---|---|---|---|
Standard | 6 | 12 | 15 |
Class 4 | 4 | 10 | 12 |
Striae
Additionally to the bulk stress birefringence, the stress birefringence induced by local striae is classified as a function of part diameter.
Stress birefringence caused by striae [nm/striae] for parts with diameters or diagonals:
< 500 mm | < 2000 mm | < 4000 mm | |
---|---|---|---|
Standard | 60 | 60 | 60 |
Class 4 | 45 | 45 | 45 |
Class 3 | 30 | 30 | 30 |
Class 2 | 5 | 30 | 30 |
Class 1 | - | 5 | 30 |
Processing
ZERODUR® is processed into complex geometries based on technical drawings and specifications from our customers. Our application and process engineers support you during the design phase of your product to get the most out of the ZERODUR® properties for your individual application. We also provide finite-element modelling and special quality requirements upon request.
5-axis CNC grinding machines allow for precise fabrication of ZERODUR® parts up to 4.25 m in diameter. The highlight of ZERODUR® processing is its light-weighting by grinding challenging aspect ratios of pocket heights to rib thickness used for parts with strict weight requirements.
By single-side and double-side polishing, we offer different surface-quality grades for dimensions up to 500 mm. Depending on the size of your part, a roughness down to the sub-nanometer range can be achieved.
As ZERODUR® acts as a very good substrate for coating, several coatings from standard aluminum to complex customized coatings are available for parts smaller than 300 mm. Our coating experts are ready to support you in choosing the coating that matches your specifications best.
Proposed CNC grinding tolerances for dimensions and shapes
Dimension < 2000 mm | Tolerances [mm] | Thighter tolerances [mm]* |
---|---|---|
Length, width, height |
± 0.3 | ± 0.1 |
Diameter | ± 0.3 | ± 0.1 |
Angle | ± 5’ | ± 1’ |
Flatness ** | 0.1 - 0.2 | 0.1 |
Cylindricity ** | 0.1 | 0.1 |
Profile ** | 0.2 | 0.1 |
Parallelism ** | 0.1 - 0.2 | 0.1 |
Position ** | 0.1 | 0.1 |
Concentricity ** | 0.1 | 0.1 |
Run-out ** | 0.1 | 0.1 |
** according ISO 1101
Dimension ≤ 4000 mm |
Tolerances [mm] |
Thighter tolerances [mm]* |
---|---|---|
Length, width, height | ± 0.4 |
± 0.2 |
Diameter | ± 0.4 | ± 0.2 |
Angle | ± 5’ | ± 1’ |
Flatness ** | 0.2 | 0.1 |
Cylindricity ** | 0.2 | 0.1 |
Profile ** | 0.4 | 0.2 |
Parallelism ** | 0.2 | 0.1 |
Position ** | 0.2 | 0.1 |
Concentricity ** | 0.2 | 0.1 |
Run-out ** | 0.2 | 0.1 |
** according ISO 1101
Physical properties
Bending stress and lifetime calculation
ZERODUR® is the material of choice when it comes to excellent thermal properties and precision in high-tech applications. Often these applications also require to withstand certain mechanical loads, such as continuously as in telescope mirror holders or short-term during rocket launch.
The key factor to be evaluated to quantify the breakage stress of ZERODUR® is the surface quality, especially the occurrence of microcracks. In general, applying loads below 10 MPa tensile stress does not demand any special breakage analysis of ZERODUR®.
SCHOTT’s exhaustive data on the breakage events of ground ZERODUR® samples has shown that it can withstand long-term (tens of years) mechanical loads of 30 to 100 MPa. This is much higher than previously predicted. Using a three-parameter Weibull distribution, we are happy to discuss the ZERODUR® lifetime under your individual long-term mechanical loads.
Typical mechanical and optical properties
ZERODUR® | ZERODUR® K20 | |
---|---|---|
Thermal conductivity λ at 20°C [W/(m・K)] | 1.46 | 1.63 |
Thermal diffusivity index a at 20°C [10-6m2/s] | 0.72 | - |
Heat capacity cp at 20°C [J/(g · K)] | 0.80 | 0.90 |
Young's modulus E at 20°C [GPa]-mean value | 90.3 | 84.7 |
Poisson‘s ratio | 0.24 | 0.25 |
Density ρ [g/cm3] | 2.53 | 2.53 |
Knoop Hardness HK 0,1/20 (ISO9385) | 0.1 - 0.2 | 0.05 |
Refractive index nd | 0.1 | 0.05 |
Abbe number νd | 0.1 | 0.05 |
Internal transmittance Ti at 580 nm / 5 mm thickness | 0.95 | - |
Internal transmittance Ti at 580 nm / 10 mm thickness | 0.9 | - |
Stress optical coefficient K at λ = 589.3 nm [10-6MPa-1] | 3 | - |
Electrical resistivity ρ at 20°C [Ω · cm] | 2.6 · 1013 | - |
Tk100 [°C], Temperature for ρ = 108 [Ω · cm] | 178 | - |
Chemical properties
At room temperature, most acids, alkalis, salts and dye solutions leave no residual traces on ZERODUR® surfaces. It can be etched by hydrofluoric acid as well as concentrated sulfuric acid at elevated temperatures. Furthermore, construction materials such as mica, chamotte, MgO and SiO2 do not react noticeably with ZERODUR® (up to 600°C for 5 h). By contrast, enamel reacts above 560°C by having its surface destroyed.
Based on the good chemical resistance of the material, coatings such as mirrors are removable in a reproducible manner. The polished surface is simply cleaned and recoated by an optimized protocol.
Typical chemical properties
ZERODUR® | ZERODUR® K20 | |
---|---|---|
Hydrolytic resistance class (ISO 719) | HGB 1 | - |
Acid resistance class (ISO 8424) | 1.0 |
- |
Alkali resistance class (ISO 10629) | 1.0 | - |
Climate resistance | Class 1 | - |
Stain resistance | Class 0 | - |
Helium permeability [Atoms/(cm · s · bar)] at 20°C | 1.6 · 106 | - |
Helium permeability [Atoms/(cm · s · bar)] at 100°C | 5.0 · 107 | - |
Helium permeability [Atoms/(cm · s · bar)] at 200°C | 7.2 · 108 | - |
Selected Publications
No. | Year | Title | Authors | Publications |
---|---|---|---|---|
[1-14] | 2018 | Advices for the use of ZERODUR® at higher temperatures | R. Jedamzik, T. Westerhoff | Proc. SPIE Vol. 10706 |
[1-13] | 2017 | Homogeneity of the coefficient of linear thermal expansion of ZERODUR: a review of a decade of evaluations | R. Jedamzik, T. Westerhoff | Proc. SPIE Vol. 10401 |
[1-12] | 2016 | ZERODUR® thermo-mechanical modelling and advanced dilatometry for the ELT generation | R. Jedamzik, C. Kunisch, T. Westerhoff | Proc. SPIE Vol. 9912 |
[1-11] | 2016 | Effects of thermal inhomogeneity on 4m class mirror substrates | R. Jedamzik, C. Kunisch, T. Westerhoff | Proc. SPIE Vol. 9912 |
[1-10] | 2016 | Progress on glass ceramic ZERODUR® enabling nanometer precision | Ralf Jedamzik, Clemens Kunisch, Johannes Nieder, Peter Weber, Thomas Westerhoff | Proc. SPIE Vol. 9780 |
[1-10] | 2016 | ZERODUR® thermo-mechanical modelling and advanced dilatometry for the ELT generation | Ralf Jedamzik, Clemens Kunisch, Thomas Westerhoff | Proc. SPIE Vol. 9912 |
[1-10] | 2016 | Next generation dilatometer for highest accuracy thermal expansion measurement of ZERODUR® | R. Jedamzik, A. Engel, C. Kunisch, G. Westenberger, P. Fischer, T. Westerhoff | Proc. SPIE Vol. 9574 |
[1-8] | 2014 | ZERODUR® TAILORED for cryogenic application | R. Jedamzik, T. Westerhoff | Proc. SPIE. Vol. 9151 |
[1-7] | 2013 | ZERODUR®: progress in CTE characterization | R. Jedamzik, C. Kunisch, T. Westerhoff | Proc. SPIE Vol. 8860 |
[1-6] | 2013 | Zero expansion glass ceramic ZERODUR® roadmap for advanced lithography | T. Westerhoff, R. Jedamzik, P. Hartmann | Proc. SPIE Vol. 8683 |
[1-5] | 2010 | Modelling of the thermal expansion behavior of ZERODUR® at arbitrary temperature profiles | R. Jedamzik, T. Johansson, T. Westerhoff | Proc. SPIE Vol. 7739 |
[1-4] | 2009 | CTE characterisation of ZERODUR® for the ELT century | R. Jedamzik, T. Döhring, T. Johansson, P. Hartmann, T. Westerhoff | Proc. SPIE Vol. 7425 |
[1-3] | 2006 | Homogeneity of the linear thermal expansion coefficient of ZERODUR® measured with improved accuracy | R. Jedamzik, R. Müller, P. Hartmann | Proc. SPIE Vol. 6273 |
[1-2] | 2006 | Influence of striae on the homogeneity of the linear thermal expansion coefficient of ZERODUR® | R. Jedamzik, P. Hartmann | Proc. SPIE Vol. 6288 |
[1-1] | 2005 | Homogeneity of the coefficient of linear thermal expansion of ZEDRODUR® | R. Jedamzik, T. Doehring, R. Mueller, P. Hartmann | Proc. SPIE Vol. 5868 |
No. | Year | Title | Authors | Publications |
---|---|---|---|---|
[2-13] | 2019 | Minimum lifetime of ZERODUR® structures based on the breakage stress threshold model: a review | Peter Hartmann | Optical Engineering Vol. 58, Issue 2 (open access) |
[2-12] | 2018 | The relation of surface treatment and sub-surface damage on ZERODUR® | R. Jedamzik, P. Hartmann, I. Burger, T. Westerhoff | Proc. SPIE Vol. 10706 |
[2-11] | 2017 | ZERODUR®-bending strength: review of achievements | P. Hartmann | Proc. SPIE Vol. 10371 |
[2-10] | 2016 | ZERODUR® strength modeling with Weibull statistical distributions | P. Hartmann | Proc. SPIE Vol. 9912 (open access) |
[2-9] | 2015 | ZERODUR®: new stress corrosion data improve strength fatigue prediction | P. Hartmann, G. Kleer | Proc. SPIE Vol. 9573 |
[2-8] |
2014 | ZERODUR®: bending strength data for etched surfaces | P. Hartmann, A. Leys, A. Carré, F. Kerz, T. Westerhoff | Proc. SPIE. Vol. 9151 |
[2-7] | 2012 | ZERODUR®, Deterministic approach for strength design | P. Hartmann | Optical Engineering 51(12) |
[2-6] |
2012 | ZERODUR® for stressed mirror polishing II: improved modeling of the material behavior | R. Jedamzik, C. Kunisch, T. Westerhoff, U. Müller, J. Daniel | Proc. SPIE Vol. 8450 |
[2-5] | 2011 | ZERODUR®: new results on bending strength and stress corrosion | P. Hartmann | Proc. SPIE Vol. 8146 |
[2-4] | 2011 | ZERODUR® for stress mirror polishing | R. Jedamzik, C. Kunisch, T. Westerhoff | Proc. SPIE Vol. 8126 |
[2-3] | 2009 | ZERODUR® glass ceramics for high stress applications |
P. Hartmann, K. Nattermann, T. Döhring, R. Jedamzik, M. Kuhr, P. Thomas, G. Kling, S. Lucarelli |
Proc. SPIE Vol. 7425 |
[2-2] | 2007 | Strength aspects for the design of ZERODUR® glass ceramics structures | P. Hartmann, K. Nattermann, T. Doehring, M. Kuhr, P. Thomas, G. Kling, P. Gath, S. Lucarelli | Proc. SPIE Vol. 6666 |
[2-1] | 2008 | ZERODUR® glass ceramics: design of structures with high mechanical stresses | K. Nattermann, P. Hartmann, G. Kling, P. Gath, S. Lucarelli, B. Messerschmidt | Proc. SPIE Vol. 7018 |
No. | Year | Title | Author | Publications |
---|---|---|---|---|
[4-18] | 2020 | ZERODUR® manufacturing capacity: ELT and more | T. Westerhoff, T. Hull, R. Jedamzik | Proc. SPIE Vol. 11116 |
[4-17] | 2020 | Establishing a substrate manufacturing center for ZERODUR 4-meter diameter lightweight mirrors | T. Westerhoff, T. Hull, R. Jedamzik | Proc. SPIE Vol. 11117 |
[4-16] | 2020 | Optimizing ZERODUR® mirror substrate fabrication processes for efficient optical fabrication | T, Hull, T. Westerhoff, R. Jedamzik | Proc. SPIE Vol. 11116 |
[4-15] | 2017 | ZERODUR® 4-m blank surviving up to 20 g acceleration | T. Westerhoff, T. Werner, T. Gehindy | Proc. SPIE Vol. 10401 |
[4-14] | 2012 | Performance of industrial scale production of ZERODUR® mirrors with diameter of 1.5 m proves readiness for the ELT M1 segments | T. Westerhoff, P. Hartmann, R. Jedamzik, A. Werz | Proc. SPIE Vol. 8444 |
[4-13] | 2012 | Zero-expansion glass ceramic ZERODUR®: recent developments reveal high potential | P. Hartmann, R. Jedamzik, T. Westerhoff | Proc. SPIE Vol. 8450 |
[4-12] | 2011 | Progress on 4 m class ZERODUR® mirror production | T. Westerhoff, S. Gruen, R. Jedamzik, C. Klein, T. Werner, A. Werz | Proc. SPIE Vol. 8126 |
[4-11] | 2010 | ZERODUR® 8 m mirror for space telescope | P. Hartmann, T. Westerhoff, R. Reiter, R. Jedamzik, V. Wittmer, H. Kohlmann | Proc. SPIE Vol. 7731 |
[4-10] | 2009 | Four decades of ZERODUR® mirror substrates for astronomy | T. Döhring, R. Jedamzik, T. Westerhoff, P. Hartmann | Proc. SPIE Vol. 7281 |
[4-9] | 2007 | Mirrors for solar telescopes made from ZERODUR® glass ceramic | T. Döhring, R. Jedamzik, P. Hartmann | Proc. SPIE Vol. 6689 |
[4-8] | 2006 | Properties of ZERODUR® mirror blanks for extremely large telescopes | T. Döhring, P. Hartmann, R. Jedamzik, A. Thomas, F.-T. Lentes | Proc. SPIE Vol. 6148 |
[4-7] | 2005 | Status of ZERODUR® mirror blank production at SCHOTT | T. Doehring, P. Hartmann, R. Jedamzik, A. Thomas | Proc. SPIE Vol. 5869 |
[4-6] | 2004 | ZERODUR® mirror blanks for ELTs: technology and production capacity at SCHOTT | T. Dohring, P. Hartmann, R. Jedamzik, A. Thomas | Proc. SPIE Vol. 5382 |
[4-5] | 2004 | Production of the 4.1-m ZERODUR® mirror blank for the VISTA Telescope | T. Doehring, R. Jedamzik, V. Wittmer, A. Thomas | Proc. SPIE Vol. 5494 |
[4-4] | 2004 | Forming mandrels for x-ray telescopes made of modified ZERODUR® | T. Doehring, R. Jedamzik, P. Hartmann, H. Esemann, C. Kunisch | Proc. SPIE Vol. 5168 |
[4-3] | 2004 | 100 years of mirror blanks from SCHOTT | P. Hartmann, H. F. Morian | Proc. SPIE Vol. 5382 |
[4-2] | 2003 | ZERODUR® mandrels for the next generation of x-ray telescopes | T. Doehring, R. Jedamzik, A. Thomas, H. F. Morian | Proc. SPIE Vol. 4851 |
[4-1] | 2003 | ZERODUR® for large segmented telescopes | H. F. Morian, P. Hartmann, R. Jedamzik, H. W. Hoeness | Proc. SPIE Vol. 4837 |
No. | Year | Title | Authors | Publications |
---|---|---|---|---|
[5-2] |
2018 | Impact of ionizing radiations on ZERODUR® | A. Carre, T. Westerhoff, T. Hull | Proc. SPIE Vol. 10698 |
[5-1] | 2017 | Review of space radiation interaction with ZERODUR® | A. Carre, T. Westerhoff, T. Hull, D. Doyle | Proc. SPIE Vol. 10401 |
