Ruby - Properties of Ruby - Supplier Data from Goodfellow

Chemical Formula

The chemical formula of Ruby is Al2O3/Cr2O3/Si2O3

Background

Ruby exhibits identical properties to those of Sapphire. Small amounts of impurities give Ruby a red colouration.

Key Properties

The key properties of Ruby are tabulated below.

Table 1. Key properties

Chemical Resistance
Acids – concentrated Good
Acids – dilute Good
Alkalis Good
Halogens Good
Metals Good
Electrical Properties
Dielectric constant 7.5 - 11.5
Dielectric strength ( kV.mm-1 ) 15 - 50
Volume resistivity @ 25 °C ( Ohm.cm ) 1014
Mechanical Properties
Compressive strength ( MPa ) 2100
Hardness - Knoop ( kgf.mm-2 ) 2000
Hardness - Vickers ( kgf.mm-2 ) 2500 - 3000
Tensile modulus ( GPa ) 350 - 390
Tensile strength ( MPa ) 250 - 400
Physical Properties
Apparent porosity ( % ) 0
Density ( g.cm-3 ) 3.98
Useful optical transmission range 150 - 5500 nm
Water absorption - saturation ( % ) 0
Thermal Properties
Coefficient of thermal expansion, 20-1000 °C ( x10-6 K-1 ) 5.8
Melting point (°C ) 2050
Specific heat @ 25 °C ( J.K-1.kg-1 ) 750
Thermal conductivity @ 20 °C ( W.m-1.K-1 ) 35 - 40
Upper continuous use temperature ( °C ) 1800 - 1950

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