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Linear thermal expansion coefficients (LTECs) of two kinds of ceramic gauge block (seven in all) and steel gauge blocks (four in all) were measured in the range-10 C to 60 C with an optical heterodyne interferometric dilatometer. The dilatometer has an uncertainty and reproducibility of the order of 1 10-9 K-1 in LTEC measurements. LTECs of (9.229 ± 0.011) 10-6 K-1 were obtained for four 2 % Al 2 O 3 partially stabilized zirconia (PSZ) gauge blocks; (9.381 ± 0.003) 10-6 K-1 for three 99.9 % PSZ gauge blocks; and (10.702 ± 0.064) 10-6 K-1 for four steel gauge blocks. These results are discussed in relation to the compositions and production batches of the gauge blocks.

A new technique to measure thermal diffusivities of solid materials, including their anisotropic behaviours, has been developed. The technique is based on periodic heating: an intensity-modulated laser beam is focused to make a small heat spot on the front side of a thin-plate specimen and the excited temperature waves are detected by a thin thermocouple attached onto its rear side. The phase lag of temperature waves is monitored as a function of the distance between the heated spot and the sensing point. The accuracy and the applicability of the present technique were well verified by using two kinds of isotropic reference samples, an austenitic stainless steel and pure copper. The typical uncertainty is estimated to be 5% at room temperature. This technique was applied to evaluate the highly anisotropic thermal diffusivity of highly oriented pyrolytic graphite (HOPG). Its anisotropy, Dab/Dc (the ratio of the in-plane thermal diffusivity to the out-of-plane one), was observed to be about 220.