Sapphire as a material

Sapphire has a rhombohedral type structure and is a highly anisotropic material.

Why choose sapphire for optics?

With a Mohs 9 hardness, sapphire is second only to diamond in its protective ability. Using modern finishing processes, sapphire can be fabricated into various configurations such as:

Sapphire Windows

Sapphire windows can include stepped edges, elliptical edge shaping, holes, slots, and wedges for mounting purposes.

Sapphire Lenses

Manufactured from optical grade grown sapphire for use in IR laser beamsteering, imaging, and focusing.

Sapphire Domes

Domes are well suited for a wide variety of applications including high speed missile domes and viewports.

Sapphire properties and applications white paper

Sapphire is a tough optical material resistant to chemicals, scratching, and high pressure in many diverse environments and has exceptional transparency. Frequently it is the combination of two, or more, of its properties that make sapphire the only material available to solve complex engineering design problems. For a white paper that details some of these properties and potential applications of sapphire:

CLICK TO VIEW/DOWNLOAD

Properties of Sapphire

The properties shown in the table below are average values for different orientations, for more detailed property information please contact us.

Mechanical

Density: 3.97g/cm3

Vickers Hardness ∥ to c-axis: 1940

Vickers Hardness ⊥ to c-axis: 2200

Tensile Strength: 60,000 psi

Compressive Strength: 300,000 psi

Young’s Modulus: 74 x 106 psi

Poisson Ratio: 0.28

Thermal

Melting Point: 2050°C

Thermal Conductivity: 32W/Mk (@258°C)

Specific Heat: 1.99 J/cm3°C)

Electrical

Resistivity: @25°C > 1018 ohm cm

@500°C > 1012 ohm cm

Dielectric Constant: Perpendicular to C axis 9.3 (KHz-I GHz, 25°)

Parallel to C axis 11.5 (KHz-I GHz, 25°)

Dielectric Strength: 480,000 v/cm

Sapphire Crystallographic Planes

A representation of sapphire’s crystal structures and important orientation planes. Click below for a more comprehensive diagram.

sapphire_crystal_diagram

Quality

Optical Grading of Sapphire

Grade 1 Sapphire

Inclusions, lineage, bubbles and twins are not permitted.

Grade 2 Sapphire

Inclusions, lineage and twins are not permitted. Micro bubbles with a diameter of 10 microns or less are permitted. (Bubbles less than 10 microns are generally not visible with the naked eye).

Grade 3 Sapphire

Inclusions, lineage and twins are not permitted. Uniformly distributed bubbles not larger than 50 microns in diameter and not closer in distance between bubbles than 500 microns are permitted.

Read more about the 8 grades of sapphire…

Want answers to a specific question, or to learn more about sapphire optics?

Sapphire Purity

The quality of sapphire is determined by how closely the grown crystal matches the ideal structure with respect to the arrangement of atoms within the lattice, dislocations, defects, and stress. The root causes for these problems often originate from insufficient purity of the starting material and the growth process itself.

Light Through Sapphire

Want to know more about the ratio of the velocity of light in a vacuum to its velocity in sapphire?

Transmittance

A graph showing the typical transmittance of sapphire.

PDF

The Masters of Sapphire Fabrication - Meller Optics, Inc. CUSTOM SAPPHIRE OPTICS FABRICATED FOR AEROSPACE APPLICATIONS

Masters of sapphire

Not only do we maintain a substantial inventory of sapphire optics, we can also manufacture optics to your exact specifications.