전하량 적정법에 의한 Ni<sub>1-X</sub>O의 Nonstoichiometry 측정

서상혁; 오승모

Journal of the Korean Industrial and Engineering Chemistry, Vol.2, No.4, 385-392, December, 1991

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전하량 적정법에 의한 Ni_1-XO의 Nonstoichiometry 측정

Coulometric Titration for the Determination of Nonstoichiometry in Ni_1-xO

서상혁, 오승모

초록

전하량적정법에 의해 Ni_1-xO 의 비화학양(nonstoichiometry)를 측정하였고 결함모델을 확인하였다. 0.1-0.21atm의 산소분압과 1123-l198K의 온도범위에서 Ni_l-xO 의 비화학양은 Po₂^1/4 에 비례하였다. 이 러한 산소분압의 의존성으로부터 Ni_l-xO의 주 결함은 singly 이온화한 Ni 빈자리임을 확인할 수 있었다. T=l173K와 Po₂=0.21atm인 조건에서 x=1.21×10^-4의 값을 가졌다. 제안된 결함모델로 부터 결함의 표준생성엔탈피를 계산하였는데 0.95 eV의 값을 가졌다. 1248K 이상의 온도에서는 doubly 이온화된 빈자리로의 전이가 나타나기 시작하였다.

Nonstoichiometry and defect model for Ni_l-xO were determined by coulometric titration method. In the temperature range of 1123-l198K and oxygen partial pressure of 0.21-0.1 atm, the nonstoichiometry was found to be proportional to the fourth root of the oxygen partial pressure. This pressure dependence can be explained by the fact that nonstoichiometric Ni_1-xO contains singly ionized metal vacancies as the predominant point defects. At T=l173K and Po₂=0.21 atm, the nonstoichiometry, x was 1.21×10^-4. The standard formation enthalpy of defects in Ni_l-xO was found, on the basis of this defect model, to be 0.95 eV. Also the result indicates that both of singly and doubly ionized metal vacancies are simultaneously present at above 1248K.

[References]

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[5] Tretyakov YD, Rapp RA, Trans. AIME., 245, 1235 (1969)

[6] Uno R, J. Phys. Soc. Jpn., 22, 1502 (1967)

[7] Bransky I, Tallan NM, J. Chem. Phys., 49, 1243 (1968)

[8] Eror NG, Wagner JB, Phys. Status Solid., 35, 641 (1969)

[9] Pizzini S, Morlotti R, J. Electrochem. Soc., 114, 1179 (1967)

[10] Osburn CM, Vest RW, J. Phys. Chem. Solids, 32, 1331 (1971)

[11] Meier GH, Rapp RA, Z. Phys. Chem. Neue Folge, 74, 168 (1971)

[12] Cox JT, Quinn CM, J. Mater. Sci., 4, 33 (1968)

[13] Volpe ML, Reddy J, J. Chem. Phys., 53, 1117 (1970)

[14] Koel GJ, Gellings PJ, Oxid. Metals, 5, 185 (1972)

[15] Ikeda Y, Nii K, Beranger G, Lacombe P, Trans. Jpn. Inst. Metals, 15, 441 (1974)

[16] Farhi R, Petot-Ervas G, J. Phys. Chem. Solids, 39, 1169 (1978)

[17] Nowotony J, Sadowski A, J. Am. Ceram. Soc., 62, 24 (1979)

[18] Peterson NL, Wiley CL, J. Phys. Chem. Solids, 46, 43 (1985)

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[20] Koumoto K, Zhang ZT, Yanagida H, Yogyo Kyokai Shi, 92, 37 (1984)