Measurement of Nonstoichiometry (x) of <TEX>$UO_{2+x}$</TEX> and <TEX>$(Er_{0.06}U_{0.94})O_{2+x}$</TEX> by a Coulometric Titration Method

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J. Korean Ceram. Soc. > Volume 34(7); 1997 > Article

Journal of the Korean Ceramic Society 1997;34(7): 722.

전하 적정법에 의한 $UO_{2+x}$ 및 $(Er_{0.06}U_{0.94})O_{2+x}$ 의 Nonstoichiometry (x) 측정

강선호, 이종호, 유한일, 김한수¹, 이영우¹

서울대학교 재료공학부
¹원자력연구소

Measurement of Nonstoichiometry (x) of $UO_{2+x}$ and $(Er_{0.06}U_{0.94})O_{2+x}$ by a Coulometric Titration Method

ABSTRACT

The nonstoichiometry (x) of UO2+x and (Er0.06U0.94)O2+x has been in-situ measure against oxygen activity (Po2) at elevated temperatures by a coulometric titration method. From the dependence of the oxygen excess (x) of UO2+x on Po2 at 1000℃, it has been concluded that (2Vo2Oia2Oib)〃〃and (2Vo2Oia2Oib)' clusters are prevailing at low oxygen partial pressure [log(Po2/atm) -10.6] and at high oxygen partial pressure [log(Po2/atm) -10.6], respectively. The nonstoichiometry is found to be reduced with the addition of Er, which is ascribed to the fact that the fixed-valent Er3+ reduces the oxidation capacities of UO2+x. The enthalpy of oxygen incorporation in (Er0.06li0.94)O2+x has been evaluated from the mean valences of U-ion as -180±70 kJ/mole.

Key words: Nonstoichiometry, $UO_{2+x}$, Er-doped $UO_{2+x}$, Coulometric titration