PELCO® Sapphire Substrate Discs


  • The PELCO® Sapphire Discs or Wafers are made from high purity clear sapphire (Al2O3), ground and optically clear polished on both sides. Sapphire has a wide transmission range; from 150 to 6000nm with low absorbance in the 300 to 4500nm range. The discs are ideal as substrates for thin film research and are suitable for optical research. Excellent resistance against a wide range of chemicals. Surface polish to one microinch or better on each face. Tolerances are ±0.001" (0.025mm) in diameter and thickness; flatness to 0.0003" (0.0008mm) or better. Available in 0.5" (12.7mm), 0.75" (19mm) and 1" (25.4mm) diameter with a choice of thickness between 0.010" or 0.125" (0.25 or 3.2mm).

    16005-0520 - Sapphire Substrate Disc, Ø12.7mm x 0.5mm (Ø0.5" x 0.020"), polished

    16005-0540 - Sapphire Substrate Disc, Ø12.7mm x 1mm (Ø0.5" x 0.040"), polished

    16005-0720 - Sapphire Substrate Disc, Ø19.0mm x 0.5mm (Ø0.75" x 0.020"), polished

    16005-0740 - Sapphire Substrate Disc, Ø19.0mm x 1.0mm (Ø0.75" x 0.040"), polished

    16005-1010 - Sapphire Substrate Disc, Ø25.4mm x 0.3mm (Ø1" x 0.010"), polished

    16005-1020 - Sapphire Substrate Disc, Ø25.4mm x 0.5mm (Ø1" x 0.020"), polished

    16005-1040 - Sapphire Substrate Disc, Ø25.4mm x 1.0mm (Ø1" x 0.040"), polished

    16005-10125 - Sapphire Substrate Disc, Ø25.4mm x 3.2mm (Ø1" x 0.125"), polished

    PELCO® Sapphire Substrate Discs, Technical Information

    Crystal Structure:
    Sapphire is an anistrophic crystal, hexagonal system, composed of unicrystalline alpha aluminum oxide, essentially 100% pure. Various properties are a function of crystallographic direction (related to the optic axis of the crystal). Sapphire discs are made from sapphire rods, the c-axis of the hexagonal unit cell is in the longitudinal direction. In the tables below, if no orientation is shown, this indicates that the property listed does not vary appreciably in relation to orientation or the variation is less than the experimental error of measurement.

    Hexagonal Unit Cell of Sapphire

    Transmission of synthetic sapphire is shown in the following curve. Data in UV region is approximate, as transmission depends on surface finish, internal quality and purity of individual specimen. The following curve shows transmission of sapphire uncorrected for Fresnel losses.

    Crystaline Structure:  Rhombohedral Single Crystal Young's Modulus:  50 to 55,000,000 PSI
    Hexagonal System:  A=4.763Å   C=13.003Å

    Melting Point:  2040°C

    Density:  3.97 g/cm³
    Bending Modulus (Minimum):
    20° C 60,000 PSI
    500° C 40,000 PSI
    1000° C 60,000 PSI
    Refractive Index:  20° C
    300nm 1.814
    400nm 1.785
    700nm 1.763
    1000nm 1.757
    2000nm 1.740
    3000nm 1.713
    4000nm 1.677
    5000nm 1.623
    Thermal Conductivity:
    12K (-261° C) = 8.0 cal/cm2/sec/C/cm
    300K (23° C) = 0.9 cal/cm2/sec/C/cm
    50° C = .07 cal/cm2/sec/C/cm

    Coefficient of Expansion
    (Mean between 20° C and T) per° C
      Perpendicular to C-axis Parallel to C-axis
    50° C .0000050 .0000067
    500° C .0000077 .0000083
    1000° C .0000083 .0000090
    Electrical Resitivity:
    20° C 1014 ohm-cm
    500° C 1011 ohm-cm
    1000° C 109 ohm-cm
    Loss Tangent:  < 1 x 10-4  at 1MHz

    Hardness:  Moh 9, Knoop 1525 to 2000
    Dielectric Constant: 11.5 at 1MHz (parallel to c-axis)
    9.3 at 1MHz (perpendicular to c-axis)
    Chemical Resistance:
    Inert to virtually all reagents at room temperatures and many at high temperatures. Essentially inert to all acids including HF, and resistant to alkalis but becoming soluble at higher temperatures.

    Sealing Characteristics:
    Sapphire can be wetted by glass, titanium, zirconium or moly-manganese mixtures. It can be matched to titanium, molybdenium, the high nickel-iron allows such as Carpenter 49, Kovar and the Corning glass 7520. With the good technique, bonds can be made directly to Corning 7052.

    As can be seen from the list of properties, sapphire is unique when compared to optical materials useful within its transmission range in that it is by far the strongest, toughest, thermal shock and chemically resistant material available, and it can be used at far higher temperatures than most optical materials. Also, its thermal conductivity is relatively high despite its extreme electrical non-conductivity. Moderate refractive index, transparency in visible region, good transmission and relatively low emission at high temperatures plus unusual stability combine to make it valuable as a component on military optics.