Abstract:

The thermal (phonon) conductivity of glass has been measured by contacting the sample with a metal at a different uniform initial temperature. The subsequent temperature response in the metal is measured by a tiny thermocouple just underneath the (contact) surface. The coefficient of heat penetration c_p follows directly from the fitted asymptotic temperature jump or drop for long times. Division by the separately measured heat capacity c_p yields the thermal conductivity . The conductivity measurement reproducibility was = 3%. The standard deviation between validation measurements and round robin test results on Pyrex glass was = 5.8%, somewhat more than the accuracy = 5.2% of the round robin test results. The measurement method is insensible for slight imperfections of the thermal contact and infrared radiation diffusion (photon conductivity) in a hot glass. The method has been used with minor modifications for solid and molten samples at temperatures of 50–850°C and conductivities of 0.1–25 W/(m K). The thermal (phonon) conductivity of the investigated soda-lime silicate glasses increases slightly (27–30%) with temperature from ambient up to around the glass transition.

Language: English

Document Type: Regular paper

Affiliations: 1: Philips Research Laboratories, Prof. Holstlaan 4, 5656 AA Eindhoven, the Netherlands