Determination of the thermal expansion coefficients of materials with a laser interferometric dilatometer

A description is given of the apparatus for measuring the thermal expansion coefficients of materials using a Fabry–Perot interferometer. The expansion coefficient is deduced from the number of resonance transmission peaks of a Fabry-Perot interferometer (these peaks are the result of coincidence with the frequency of a stabilized laser when the temperature of the sample is varied). A simple method is used in the determination of the sign of the expansion coefficient. Hermetic sealing of an inner cavity drilled through a sample dispenses with the need for evacuation of the Fabry–Perot interferometer and makes it possible to use various heat carriers in the thermal stabilization of the sample. The expansion coefficient over a range of 10°C can be determined to within ±1×10^–7 deg^–1.