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SPINEL AND OPTICAL CERAMICS - PROPERTIES
Spinel Properties - Higher optical transmission in the MWIR at 4.8µm is driving the development of spinel for future seeker and E/O imaging systems. Spinel dielectric properties also make it an attractive choice for radar and RF communications applications as well as combined laser/RF communications. The high hardness of transparent spinel provides enhanced rain and sand erosion resistance as well as outstanding ballistic protection capabilities.
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% improvement in transmission over sapphire and ALON at 4.8 microns |
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(°C) |
Sapphire |
ALON |
| 25 |
4% |
8% |
| 250 |
5% |
9% |
| 500 |
5% |
13% |
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PROPERTIES |
Spinel |
ALON™ |
Sapphire |
Quartz |
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Density, g/cc |
3.58 |
3.69 |
3.97 |
2.21 |
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Grain size, µm |
50-75 |
250 |
single crystal |
amorphous |
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Color |
transparent |
transparent |
transparent |
transparent |
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Flexural Strength, MPa (ksi) |
120-350 |
380 (55) |
742 (107.7) |
48 (7) |
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Fracture Toughness, MPa-m1/2 |
1.9 |
2 |
2 |
0.8 |
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Knoop Hardness (kg/mm2) |
1645 |
1950 |
2200 |
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Elastic Modulus, GPa (psi x 106) |
275 (39.6) |
334 (48.4) |
344 (49.8) |
70 (10.1) |
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Shear Modulus, GPa (psi x 106) |
110 (15.9) |
135 (19.6) |
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Poisson's Ratio |
0.26 |
0.239 |
0.27 |
0.16 |
Thermal Conductivity, W/m-K
(cal/cm-sec-°C) |
14.6 |
12.6 (0.023) |
24 |
1.6 |
Coefficient of Thermal Exp.
(30-900 °C); 10-6/°C |
8.0 |
7.8 |
8.8 |
0.45 |
Specific Heat, J/Kg-K
(cal/g-°C) |
(0.21) |
0.77 (0.22) |
0.75 (0.21) |
(0.22) |
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Transmission Range, µm |
0.2-6.5 |
0.22-6.0 |
0.2-6.0 |
0.2-4.5 |
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Dielectric Constant |
8.3 @ 9.3 GHz |
9.1 @ 3.044 GHz |
9.3-11.4 @ 1MHz |
3.8 @ 1MHz |
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