Dilatometry under high pressure

In order to measure anisotropic compressibilities and thermal expansion of cubic, tetragonal or orthorhombic single crystals under pressure we have mi niaturized a high resolution capacitive dilatometer and integrated this dev ice in a high pressure cell within a cryostat which allows a temperature va riation from 10K to 320K. To minimize the number of electrical lead-through s from ambient pressure to the high pressure volume we did not use the thre e terminal method but used the dilatometer type of Meingast et al. [1]. The electrical lead-through of the triaxial cable was realized by using a doub le Bridgman cone-type lead-through. One of the two capacitance plates is fi xed. The other plate is connected to a piston which is mounted with a paral lel spring suspension to enable a parallel and frictionless motion of the p iston and the capacitor plate. Length changes of a sample are transferred t o the piston which enables a high resolution measurement of length changes by monitoring the capacitance changes. Length changes of about DeltaL/L = 1 0(-8) can be resolved for a typical sample length of 1 mm.