3.5 Linear Coefficient of Thermal Expansion ()

The thermal expansion curve is obtained by measuring a well-annealed glass rod of 4 mm diameter by 50 mm long heated at a rate of 2°C/min in the low temperature range and at a rate of 4°C/min in the high temperature range. From the temperature and elongation of the sample glass, the mean linear coefficient of thermal expansion between -30°C to +70°C and +100°C to +300°C is determined with a resolution up to 10^-7 /°C and given on each technical data sheet.

3.6 Thermal Conductivity (k)

At room temperature, the thermal conductivity of most optical glasses is located between 1.126 W/(m·K) which is that of S-BSL7 and 0.546 W/(m·K) which is that of PBH71. The thermal conductivity is measured in accordance with methods prescribed in JIS-R2618. The thermal conductivity of glass at 35°C is listed in the catalogue. Accuracy is ± 5%.