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.