INTERFEROMETRIC MEASUREMENT OF THERMAL EXPANSION OF SILVER AND PALLADIUM AT LOW TEMPERATURES

The linear thermal expansion coefficients of silver and palladium have been measured in the temperature range 20°K to 273°K by an interferometric method. Photomultiplier detection was used and gas pressure changes were employed to effect changes in optical path, permitting the detection of length changes of 10 . The results of the investigation have been used in conjunction with earlier heat capacity and elasticity data to calculate the Grüneisen parameters, for which the available evidence suggests falls with falling temperature. The maximum frequencies of the Debye distributions having the same nth moments as the actual metals have also been calculated for -3 ≤ n ≤ 6, from which it is concluded that the low frequency modes play a more important role in silver than in palladium. © 1968 Iliffe Science and Technology Publications Limited.