Many optical applications require a substrate material with a near-zero coefficient of thermal expansion and/or excellent thermal shock resistance. Astrosital, equivalent to Zerodur™ (registered trademark of Schott Glass Technologies) is a glass-ceramic material with ultra low thermal expansion.
Astronomical and x-ray telescope mirrors are prime examples of application. Another well known application is production of mirror substrates for microlithography.
Maximum available size: 2,000 mm Dia (or 1,000 mm Square) x 300 mm thick.
Main Properties
Astrosital | Zerodur | |
Coefficient of linear thermal expansion, 1/K from 213K to 333K from 293K to 573K |
|
0.5 (+/-1) x 10-7 |
Density, g/cm3 at 293 K |
2.46 |
2.53 |
Young's Modulus, GPa |
90.2 |
91 |
Poisson's Ratio |
0.28 |
0.24 |
Bending Strength, GPa |
166 |
|
Relative to BK-7 abrasion hardness |
1.78 |
|
Specific Heat, kJ/(kg K) |
0.92 |
|
Thermal Conductivity, W/(m K) |
1.71 |
|
Heat Resistance, K | 823 | |
Refractive Index, nd | 1.536 +/- 0.004 | |
Mean Dispersion, nf - nc | 0.0102 +/- 0.0003 |
THERMAL PROPERTIES | ||
mean linear coefficient of thermal expansion (CTE) within temperature range -60 to 60 oС |
10-7 oC-1 | 0±1.5 |
CTE homogeneity | 10-7 oC-1 | <= 0.2 |
specific heat capacity | kilocalorie kg-1 oC-1 | 0.22 |
heat conductivity | kilocalorie h-1 m-1 oC-1 | 1.71 |
thermal resistance | oC | 550 |
MECHANICAL PROPERTIES | ||
density | g cm-3 | 2.46 |
micro hardness | 10-7Pa | 860 |
lapping relative hardness (with reference to glass, K-8 type) | - | 1.78 |
modulus of elasticity (Young’s) | GPa | 92 |
bending strength | 10-7Pa | 16.6 |
Poisson’s coefficient | - | 0.28 |
OPTICAL PROPERTIES | ||
refractive index ne | - | 1.538 |
refractive index nd | - | 1.536 |
average variance nF - nC | - | 0.0102 |
quality | - | as per requirements |
bubbles and striae | - | as per requirements |
stress birefringence | nm/cm | up to 15 |