The volumetric, electrical etc. properties of samples under
compression as a rule depend on the experimental conditions -
dimensions of sample , kind of pressure-transmitting medium.
P.W.Bridgman pointed out, that the volume V change during the phase
transitions, in contrary to the resistivity r , doesn't depend on the
non-hydrostatic component of stress in pressure medium and the shape
of sample . He recommended to perform the investigation of several
entities of substances at high pressure P . At the phase transition
region the influence of phase inclusions on different properties is
sufficiently distinguished. For example, during the structural
transition of single crystals HgSe from gapless to wide-gap
semiconductor the jump of resistance r is approximately 4-6 orders of
magnitude, while thermoelectric power S , Hall constant R and
temperature and magnetic field dependencies of r  are almost
unchanged. The clear explanation of this discrepancy was proposed
based on ordered inclusions model with the varied configuration of
To improve the accuracy of pressure testing
the combined technique of pressure investigation is proposed
- the simultaneous measurements of several properties: V, T, P, r , S
- parallel testing of various effects: S(P), Magnetoresistance MR, R
and r (T) etc. through the stationary and non-stationary methods
- exploring the different pressure apparatuses: piston-cylinder,
anvils, toroidal chambers with pressure media of various plasticity
The high pressure apparatuses containing the RAM for data keeping with
synthetic diamond and boron nitride superhard anvils [4,5],
piston-cylinder chambers made from nonmagnetic titanium alloys ,
and solid media apparatuses with the steel, tungsten carbide and hard
alloys toroidal plungers [3-5] are using for pressure generation. The
results of testing of known and novel materials by the proposed
combined technique are represented. The main features of the initial
and high pressure phases and heterophase states are determined. The
analysis was done of influence of concentration and configuration of
inclusions on the various properties of high pressure phases.
1. W.Paul, D. Warschauer (editors), Solids under pressure, McGRAW-HILL
Book Company, N.Y.,..-L., 1963.
2. S.Porowski et. al, Phys.Stat.Sol., 5, K71-K72 (1964).
3. V.V.Shchennikov et. al, Fizika Tverdogo Tela (St.-Peterburg), 37,
1015 (1995);.37, 448 (1995).
4. V.V.Shchennikov et al. in: High Pressure Chemical Engineering,
edited by R. v. Ror , Elseiver, Amsterdam, 1996, p. 667.
5. V.V.Shchennikov et al. in: Proceedings of the Fifth International
Symposium on Diamond Materials, edited by J.L. Davidson et al, The
Electrochemical Society, Inc., Pennington, NJ, 97-32, 597 (1997).