Applicability of platinum and molybdenum coatings for measuring thermal diffusivity of transparent glass specimens by the laser flash method at high temperatures

For transparent materials such as silicate glasses, an absorber layer of a laser beam and an emitter layer of an infrared ray are essentially required for measuring thermal diffusivity by the laser flash method with an infrared ray detector. Platinum (thickness: 1.0 μm) and molybdenum (thickness: 0.7 μm) thin layers were formed by sputtering on both sides of a transparent specimen with a disk shape. Then such metal coating was tested at elevated temperatures. The platinum thin layer was found to work well to measure thermal diffusivity of silica glass at temperature below 1000 K. The molybdenum coating was also successfully applied to the measurement of thermal diffusivity for silicate glass in the temperature range between 750 and 1569 K with considering radiative heat transfer inside the specimen.