화학조성에 따른 PbSnTe계 반도체의 열전 특성조사

오규환; 오승모

Journal of the Korean Industrial and Engineering Chemistry, Vol.1, No.1, 83-90, October, 1990

Export Citation

화학조성에 따른 PbSnTe계 반도체의 열전 특성조사

Chemical Analysis and Thermoelectric Properties of the PbSnTe Semiconductors

오규환, 오승모

초록

PbTe, SnTe, PbSnTe계 반도체는 저온 열전재료로서 이들의 화학조성과 비화학양(nonstoichiometry)은 열전 특성에 중요한 인자가 된다. 본 연구에서는 (Pb₁ _χSn_χ)₁ _yTe_y의 x=0.1, 0.2, 0.3, 0.4, 0.5인 고용체 시편을 제조하여 이들의 조성을 분석하고 화학조성과 전기전도도 및 열기전력과의 상관 관계를 조사하였다. 조성분석을 위하여 Pb의 함량은 EDTA와 Pb(Ⅱ) 표준용액을 이용한 착화합물 역적정법을, Te의 함량은 KMnO₄와 Fe(Ⅱ)표준용액을 이용한 산화환원 역적정법을 사용하였다. 또한 300K-750K의 온도범위에서 직류 4접점법에 의해 전기전도도를, Heat Pulse법에 의해 열기전력을 측정하였다. 모든 시편은 금속성분 (Pb+Sn) 보다는 Te의 양이 많은 비화학양의 조성을 보이며 p- 형의 반도성을 가졌고 주석의 함량이 증가할수록 비화학양도 증가하였다. 열기전력의 측정으로 시편의 주 전하나르개는 정공임을 확인할 수 있었고 비화학양에 따른 열기전력의 변화를 saturation 영역 내에서 온도에 따른 Fermi Level의 변화폭과 관련지어 설명하였다. x=0.1인 시편은 약 670K 에서 p- 형으로부터 n-형으로 전도특성이 전환되었는데 이는 이온도에서 saturation영역에서 intrinsic영역으로 전이되며 전자의 이동도가 정공의 이동도보다 크다는 사실로부터 설명되었다.

The semiconducting (Pb_l _χSn_χ)₁ _yTe_y, one of the low - temperature thermoelectric materials, has been prepared and its chemical composition and nonstoichiometry has been analyzed. The content of Pb in the specimens was determined by the complexometric back- titration method with EDTA and Pb(Ⅱ) standard solutions. Te-content was analyzed with the redox titration method. The electrical conductivity and the thermoelectric power have also been measured by the DC 4-probe and the heat-pulse technique, respectively. All of the specimens showed a nonstoichiometric behavior in their chemical compositions (Te excess), thus gave rise to a p-type semiconducting property, and the nonstoichoimetry became bigger as the Sn-content increased. The thermoelectric power vs. temperature results have been analyzed upon the basis of the Fermi level vs. temperature profiles in the saturation regime. The specimen of x=0.1 evolved a transition from p- to n- type property at about 670K, which has been explained by the fact that the mobility of electrons is bigger than that of holes in the temperature range of the intrinsic regime.

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[2] Harman TC, J. Phys. Chem. Solids, 32, 363 (1971)

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[4] Logothesis EM, Holloway H, J. Appl. Phys., 43, 256 (1972)

[5] Machnis AA, Cadoff IB, Trans. Met. Soc. AIME, 230, 333 (1964)

[6] Brebrick RF, Allgaier RS, J. Chem. Phys., 32, 1826 (1960)

[7] Brebrick RF, Gubner E, J. Chem. Phys., 36, 1283 (1962)

[8] Brebrick RF, J. Phys. Chem. Solids, 24, 27 (1963)

[9] Brebrick RF, J. Phys. Chem. Solids, 32, 551 (1971)

[10] Cheng KL, Anal. Chem., 33, 761 (1961)

[11] Cornwell JC, Cheng KL, Anal. Chim. Acta, 42, 189 (1968)

[12] Kolthoff IM, "Quantitative Chemical Analysis," Macmillan, pp. 833-834 (1971)

[13] Kim DR, "Thermoelectric Characterization in PbTe," Master Thesis, Seoul National University (1989)

[14] Oh KW, "Compositional Analysis and Thermoelectric Properties of Low Temperature Thermoelectric Semiconductor PbSnTe," Master Thesis, Seoul National University (1990)

[15] Sze SM, "Semiconductor Devices: Physics and Technology," John Wiley & Sons, pp. 1-29 (1985)

[16] Wagner C, Prog. Solid State Chem., 7, 137 (1972)

[17] McKelvey JP, "Solid State and Semiconductor Physics," Harper and Row, p. 266 (1966)

[18] Hamnett A, "Transport Measurements," in Solid State Chemistry: Techniques, Eds., A.K. Cheetham and P. Day, Charendon Press, pp. 279-321 (1987)