| SM ISO690:2012|
KTYSKOV, Ts. ; LYUBA, T.; OPTASYUK, S.; RACHKOVSKY, O.; TSYKANIUK, B.. Thermoelectric power factor of multicomponent solid solutions based on telluride germanium. In: Materials Science and Condensed Matter Physics. Editia a 7-a, 16-19 septembrie 2014, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2014, p. 111.
|Materials Science and Condensed Matter Physics
Editia a 7-a, 2014
Conferința "Materials Science and Condensed Matter Physics" |
Chișinău, Moldova, 16-19 septembrie 2014
Ge1manium telluride and its alloys are efficient materials for the1moelectrics. Stoichiometric GeTe c1ystallizes with an excess of free p-type caniers. The high concentration of charge caiTiers in Ge Te can be explained by the fact that during crystallization the excess Te atoms act as acceptors, f01ming additional holes in the valence band [I]. Samples of GeTe and Geo,99Bio,01Te, Geo,90Pbo,osBio,02Te, Geo,94Pbo,o3Bio,o3Te were synthesized for investigating their the1moelectric properties. Synthesis of compounds by direct fusion method with mixing of components was canied out in closed systems (quartz ampoules) with using substances of B-4 class. From the samples were fonned compacts by grinding and pressing at pressure 0,6 GPa. Temperature dependence of the1moemf and specific conductivity were dete1mined by standai·d methods [I]. Results, submitted on the graph (fig.I, a), show that the admixture of bismuth in solid solutions based on Ge Te leads to an increase ofthe1moemf throughout the temperature range. From the temperature dependences cr (T) (fig.I, a) shows that the introduction of Pb and Bi impurities and their concentration leads not only to a decrease of conductivity, but also changes the appearance of dependence cr (T). The1moelectric power factor value w = a2<:Y was calculated and its temperature dependence obtained from the experimental data. From the dependence W (T) (fig.I, b) shows that the coefficient of the1moemf has the greatest effect on the1moelectric power factor. The decrease of conductivity and, consequently, the the1moelectric power factor with increasing temperature can be explained by the fact that the introduction of amphoteric impurities of Bi leads to a decrease of the concentration of free charge carriers (holes). The value of cr decreases with increasing content of bismuth in solid solution. Isoelectronic impurity of Pb allows to reducing the thermal conductivity of solid solutions. A significant increase of the coefficient of the1moemf can be explained within the model of resonant states [I]. High density of new quasipaiticles with large effective mass is fo1med near the Fe1mi level with increasing of temperature. Through the introduction of Bi and Pb these atoms begin to form the impurity states which cause the compensation of free holes. Therefore, the significant increase of the coefficient of the1moemf observes in working range.