Effective Mass of Holes in Ag 0.82 Sb 1.18 Te 2.18 and AgSbTe 2
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EFFECTIVE MASS OF HOLES IN Ag0.82Sb1.18Te2.18 AND AgSbTe2 S. S. Ragimov,1,2 A. E. Babaeva,2 A. I. Alieva,2 and R. I. Selim-Zade2
UDC 538.93
Temperature dependences of the Hall and Seebeck coefficients in Ag0.82Sb1.18Te2.18 and AgSbTe2 are studied in the temperature range 4.2–320 K. It is found that the Hall coefficient in Ag0.82Sb1.18Te2.18 does not depend on the magnetic field, while for AgSbTe2, a weak dependence on the magnetic field is observed. The effective mass of holes (m* = 0.61m0) in Ag0.82Sb1.18Te2.18 is determined. Keywords: thermoelectric material, Hall coefficient, Seebeck coefficients, effective mass.
INTRODUCTION AgSbTe2 is a p-type thermoelectric material and has been studied by many authors [1–10]. Research is mainly aimed at improving the thermoelectric efficiency of this material, which is determined by the dimensionless quantity ZT = S2σT/k, where S, σ, T, and k are the Seebeck coefficient, electrical conductivity, absolute temperature, and thermal conductivity, respectively. As one can see, the high-quality thermoelectric material should have high values of electrical conductivity and thermo-emf, as well as low thermal conductivity. Studies of galvanomagnetic and thermoelectric properties make it possible to identify the conditions for optimizing and improving the characteristics of thermoelements, as well as to obtain information on the mechanisms of conductivity, features of the band structure, and parameters of charge carriers, such as the concentration, effective mass, and mobility. Note that electrical conductivity and Seebeck coefficient are determined only by the electronic properties of the material. Performing simple calculations, it can be shown that the efficiency is determined by three parameters such as the effective mass of carriers m*, their mobility µ, and thermal conductivity of the material: Zmax ~ m3/2·µ/k. Thus, to achieve the maximum values of Z, it is desirable to have high values of the mobility and effective mass of charge carriers. The effective mass of charge carriers in AgSbTe2 was estimated in several works [5, 6, 9, and 10]. Unfortunately, the values of m* of charge carriers obtained in these works vary significantly, are often overestimated, and there is no analysis of the data obtained. This work is devoted to the study and analysis of the effective mass of charge carriers in a monophase Ag0.82Sb1.18Te2.18.
EXPERIMENTAL RESULTS AND DISCUSSION The samples under study were obtained by fusing the initial components in sealed quartz ampoules and holding at 100 K above the melting temperature for 10 h with further slow cooling to room temperature at a rate of 1 K/min.
1
Institute of Physical Problems of Baku State University, Baku, Azerbaijan Republic, e-mail: [email protected]; 2Institute of Physics of Azerbaijan National Academy of Sciences, Baku, Azerbaijan Republic, e-mail: [email protected]; [email protected]; [email protected]. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 150–153, May, 2020. Origina
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