thermoelectrics of n-type conductivity have been prepared by the microwave-solvothermal method and spark plasma sintering. These compounds behave as degenerate semiconductors from room temperature up to temperature T d % 470 K. Within this temperature range the temperature behavior of the specific electrical resistivity is due to the temperature changes of electron mobility determined by acoustic and optical phonon scattering. Above T d , an onset of intrinsic conductivity takes place when electrons and holes are present. At the Lu and Tm doping, the Seebeck coefficient increases, while the specific electrical resistivity and total thermal conductivity decrease within the temperature 290-630 K range. The increase of the electrical resistivity is related to the increase of electron concentration since the Tm and Lu atoms are donor centres in the Bi 2 Te 3 lattice. The increase of the density-of-state effective mass for conduction band can be responsible for the increase of the Seebeck coefficient. The decrease of the total thermal conductivity in doped Bi 2 Te 3 is attributed to point defects like the antisite defects and Lu or Tm atoms substituting for the Bi sites. In addition, reducing the electron thermal conductivity due to forming a narrow impurity (Lu or Tm) band having high and sharp density-ofstates near the Fermi level can effectively decrease the total thermal conductivity. The thermoelectric figure-of-merit is enhanced from $ 0.4 for undoped Bi 2 Te 3 up to $ 0.7 for Bi 1.
The temperature dependence of the specific electrical resistivity, ρ, of the Bi1.9Lu0.1Te3 alloy has been studied within the temperature 2 ÷ 230 K interval. Minimum in the resistivity was found at temperature Tm 11 K. This minimum is originated from a change of conductivity mechanism. Above Tm, the resistivity ρ increases as temperature increases. This behavior is due to the electron mobility decrease via an acoustic phonon scattering at heating. Below Tm, the variable-range hopping conductivity based on electron tunneling takes place. In this case, ρ increases as temperature decreases. Two electric field regimes of the hopping conductivity were observed in the resistivity versus electric field strength dependences.
Нанопорошки Bi2Te3 и R0.1Bi1.9Te3 (где R=Er, Tm, Yb, Lu) были получены методом сольвотермально-микроволного синтеза. Порошкообразные материалы компактировали методом холодного изостатического прессования с последующим отжигом в инертной среде аргона. Изучено влияние легирующей добавки редкоземельных элементов на структуру и свойства получаемых материалов. Показано, что введение в решетку теллурида висмута атома редкоземельного элемента (2 ат%) приводит к снижению удельного электрического сопротивления и к росту значений коэффициента Зеебека. Установлено, что в исследованном ряду редкоземельных элементов наилучшие свойства проявляет образец теллурида висмута, легированный тулием. DOI: 10.21883/FTP.2017.06.44548.07
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