In the present work the technique of the high-pressure thermoelectric (TE) investigation has been developed for the phase transition recording at Si and the values of thermopower (S) for the different high pressure and metastable phases of Si have been obtained using the automated high-pressure set-up. The TE properties of various phases and states of Si were established which may be potentially used in Si-based nano-devices [1, 2]. The technique was shown also to be sensitive to the pre-treatments applied to a sample including annealing, doping, and irradiation by high-energy particles. The band structure calculations of the several phases of Si were carried out using linear muffin-tin orbital method (LMTO). The experimental values of thermoelectric power of various phases of Si up to 25 GPa are compared with the theoretical estimations basing on the band structure calculations performed. The theoretical calculations have confirmed the principal role of the contribution of d-band both in the forming of the electron states in the vicinity of Fermi level, as well as in the positive sign and the value of a thermoelectric power.
The recent progress in creation of materials with negative refractive index inaccessible for natural substances show
all-important role of the multi-phase materials in modern technology. In the present work the approach for calculating of
effective properties is considered for multi-component composite materials with variable configurations and
concentration of inclusions . The approach is based on interpolation formulas obtained between the rigorously
calculated limiting borders . The general merit of the model is the ability to obtain algebraic formulas for complicated
properties with the vectors of electrical, thermal, magnetic, etc. fields directed along the different axes . The examples
of application of the above model are given for the analysis of multi-phase states in the vicinity of pressure-induced
phase transition. The model was used for a set of semiconductor compounds like PbX, SmX (X - Te, Se, S), iron ore, etc.
. The program for calculation of different electrical, thermal, mechanical etc. properties of n-phase systems with
variety of configuration and concentration of phase inclusions has been created, which may be applicable for real multiphase
Multi-component systems (heterophases, layered, porous, misfit, composite) present the interest for different spheres of science and engineering. The paper covers both theoretical and experimental investigations of such systems with varying concentration and configuration of inclusions. En equations describing the dependence of electronic properties (thermomagnetic and galvanomagnetic as well as electrical and thermoelectric ones) of such systems on concentration and configuration of inclusions are presented. The equations derived may be used for analysis of electronic properties of advanced heterostructures. The above model describing the dependence of electronic properties of multi-component heterophase systems on concentration and configurations of inclusions allows to point out the ways for improving of electronic properties (thermoelectric effectiveness, thermoelectric and thermomagnetic figure of merit, etc.) and for extending of functional possibilities of such systems. So, the approach offered may be used for optimization of properties and for design of microdevices with improved characteristics.
The work was partly supported by the Russian Foundation for Basic Research (RFBR), Gr. No. 01 - 02 - 17203.