Modulation Dilatometry

Abstract

At present, methods for measuring the dilatation of solids provide sensitivity of the order of 10^-10 m and even better. However, difficulties of high-temperature dilatometry are caused by the plastic deformation of the samples rather than by the lack of sensitivity. This is why one had to accept data on thermal expansivity averaged over wide temperature intervals. Important improvements in this field have been made in the last decades. Along with a significant progress in traditional dilatometry, two new techniques appeared, modulation dilatometry and dynamic technique. Modulation dilatometry allows determinations of the linear thermal expansivity with small temperature oscillations and thus greatly improves the resolution of dilatometric measurements. This technique seems to be very useful because it ignores irregular external disturbances and senses only what is necessary for determining the thermal expansivity. Modulation dilatometry is applicable to conducting and nonconducting materials and in wide temperature ranges, and very sensitive methods exist for measuring extremely small periodic displacements.