On the Changing of Thermoelectric Material Properties at Large Heat Fluxes
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ON THE CHANGING OF THERMOELECTRIC MATERIAL PROPERTIES AT LARGE HEAT FLUXES LUKYAN I.
ANATYCHUK,
LEV P.
BULAT
Institute of Thermoelectricity,
Chernovtsy,
274000,
USSR
One of the main trends of the thermoelectric instrument-making development is the microminiaturization of instruments and devices.
Thermoelectric converter compactness is
achieved by this.
As thermoelement geometric dimentions redce, temperature gradients in materials increase.
From this it
follows the research
problem directed at the investigation of transport phenomena in thermoelectric materials at sufficiently large heat fluxes. Enthusiasm on investigation statement is
warmed by the consideration
about possible improvement of the efficiency at thermoelectric convertion when in
of 10
6
-_i9 V/cm
thermoelectric materials temperature gradients /1/
have been realized.
In the present paper the changing of thermoelectric material properties have been analyzed under the influence of referred considerations. It
is well-known
large heat fluxes
that in the semiconductor materials at the current carrier heating by temperature
gradient has been realized that causes the change of all kinetic properties and influences on energetic characteristics of semiconductor thermoelements
. As for thermoelectric energy con-
vertion the semiconductor materials with not very low concentration of current carrier /8/ lity
in carrier subsystem /9/
that corresponds to control availabiare of interest.
In this case for
calculation of carrier and phonon temperature distribution in semiconductor sample one can use the system of energy balance equation for carriers (for electron definiteness) and phonons in
Mat. Res. Soc. Symp. Proc. Vol. 234. 01991 Materials Research Society
72
view of energetic electron-phonon interaction as well as the continuity equation for curreat
electron heating by temperatu-
re should be also tacen into consideration /3-5/ Let us examine a the~noelectric circuit consisting of homogeneous isotropic semiconductor plate 2a in Rs,
length,
closed on load resistance Rm. The problem is
one-dimentional.
resistance of supposed to be
the origine of coordinate! x is matched with
the middle of the plate. Referred equation system in view of temperature dependences of all 'inetic
coefficients can be cal-
culated by means of determined temperatures Te,ph and all the members of equation system resolution along the parameter r
/6/
z
where T1 ,2 is
the temperature at the ends of themoelement legs
(at x=± a). As a result it
can be obtained the equations for electrons Te(x)
and phonons Tph(x) temperatures with the help of which electron and phonon heat flux
densities can be determined
as well as the cotal heat flux
ýX -ýq,IT)-tý)'#
that in necessary to ;know for efficiency calculation. The latter can be determined by the formula (3)
a____
In
(
ee) h (Teph) are the electron and phonon heat conducti-
vity coefftcients, ol (Te) is the thermoelectric coefficient e a semiconductor, is the current density.
of
Not dwellin
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