Chemical Composition

Physical Properties

SiO2 = 80.6%

Coefficient of expansion  (20°C–300°C) 3.3 x 10-6 K-1

B2O3 = 13.0%

Density 2.23g/cm3

Na2O = 4.0%

Refractive index (Sodium D line)1.474

Al2O3 = 2.3%

Dielectric constant (1MHz, 20°C) 4.6

Optical Information

Specific heat (20°C) 750J/kg°C

Refractive index (Sodium D line) =1.474

Thermal conductivity (20°C) 1.14W/m°C

Visible light transmission, 2mm thick glass = 92%

Poisson’s Ratio (25°C – 400°C) 0.2

Visible light transmission, 5mm thick glass= 91%

Young’s Modulus (25°C) 6400 kg/mm2