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Sapphire single crystals
Large single crystals of Sapphire (and other crystals such as Ruby, Garnet, etc.) grown by the Horizontal Directed Crystallization Method (dimensions 250 x 150 x 20-30 mm).
Features:
high melting point, extremely hard and resistant to abrasion, low dielectric constant - excellent electroinsulating properties, low friction coefficient, shock resistant, high refractive index, broad optical transparency (from UV to IR), chemically inert and stable
Applications:
optics, optoelectronics, micro-electronics, semiconductors, epitaxial structures, chemical industry, blanks, special windows, substrates, rods, ribbons, components of machinery and equipment, such as scanners, compasses, gyroscopes, water and electrical meters, relays and watches (exposed to severe mechanical stress and /or abrasion) and other special applications.
Basic properties:
| Physical properties: | |
| Chemical formula | - Al2O3 |
| Molecular weight | 101.96 g.mol-1 |
| Symmetry | R3c |
| a = 4.7589Å> | |
| c = 12.99Å | |
| Specific mass | 3 974 kg.m-3 |
| Thermal properties: | |
| Melting point | 2 323 K |
| Heat conductivity | 23 Wm-1K-1 (at 20 °C)> |
| Thermal expansion | 5.0 x 10-6 K-1 |
| Maximum temperature of application | 1 850° - 1 920°C |
| Mechanical properties: | |
| Mohs hardness | 9 - 9.4 |
| Knoop hardness | 2 100 kg.mm-2 (parallel to c-axis) |
| 1 800 kg.mm-2 (perpendicular to c-axis) | |
| Tensile strength | 415 MPa |
| Compression strength | 2 000 MPa |
| Bending strength | 700 MPa |
| Other special applications | |
| Coefficient of friction | |
| - with steel | 0.14 |
| - with graphite | 0.16 |
| - with bearing metal | 0.19 |
| Electrical properties: | |
| Dielectric constant | tag = 0.001 c-axis |
| Specific resistance | 1015 Ohm cm (20 °C) |
| 1011 Ohm cm (500 °C) | |
| 109 Ohm cm (1 000 °C) | |
| 103 Ohm cm (2 000 °C) | |
| Optical properties: | |
| Refractive index at 598 nm | 1.7064 (parallel c-axis) |
| 1.7680 (perpendicular c-axis) | |
| Transmission | 0.17 - 6.5 µm |
| Chemical properties: | |
| Solubility | insoluble in common bases and acids under 1300° K |
| (is attacked only by HF and H3P04 at above 600° K) | |
| Chemical stability | stable in contact with W, Mo, SiC |
| (in O2 absence) up to melting point | |
