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2004年国际稀土研究应用研讨会

作者： YANG Jiangrong, WANG Xiaolin, XIAO Hong, ZHOU Wei, JIANG Chunli,LU Lei (China Academy of Engineering Physics, P.O.Box 919-71,Mianyang, P.R.China, 621900)

lanthanum and cerium are the first two , and the most reactive , members of the lanthanide series. In particular ,cerium exhibits a variety of interesting phenomena under various conditions. Besides being an antiferromagnet, a superconductor, and a mixed valence system, it is the one pure element to exhibit Kondo scattering and a solid-solid critical point. The phenomena occur because the energy of the inner 4f lever is nearly the same as those of the outer 5d and 6s levers, and only small amounts of energy are required to change the relative occupancy of the electronic levels giving rise to a variable electronic structure. Due to the 4f levels are very close to that of 5d and 6s, cerium is quite sensitive to external influence such as temperature, pressure and chemical environment. In this present paper, Auger Electron Spectroscopy has been used to characterize the initial oxidation of ce-5wt.%la alloy in an oxygen atmosphere at low pressure(0-6Pa) and room temperature after cleaning the surface by Ar+ -ion bombardment. It is conclude from this work that oxidation proceeds as follows: (a)dissociative chemisorption for oxygen exposure lower that 5L(langmuir), and the kinetics of oxidation follows a linear law;(b) formation of oxide layer between 5 and 25L, and its growth follows a parabolic relationship;(c) thickening of the oxide film grown in the previous stage, and the uptake of oxygen reachs saturation at oxygen exposure of 25L,and the oxide film mainly consists of ce2O3, no ceO2 evidence was observed lower than 60L.

关键词： Auger Electron Spectroscopy Oxidation ce-la alloy

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Thermodynamic modelling and applications of ce-la-O phase diagram

引用

Transactions of Nonferrous Metals Society of China 2011年第12期21卷 2671-2676页

作者：龚伟平张瑞陈忠胜中南大学粉末冶金国家重点实验室长沙410083 惠州学院电子科学系惠州516001

The ce-la-O system was investigated via experiments and thermodynamic modeling. A series of ceO2-laO1.5 mixtures were prepared by co-precipitation technique and examined by X-ray diffraction. Mutual solubilities between laO1.5 and ceO2 at 1273 K were determined. Using the new experimental data together with literature information, a set of self-consistent thermodynamic parameters for the ceO2-laO1.5 system were optimized. Combined with thermodynamic descriptions of ce-O and la-O systems from literature, several property diagrams of ce-la-O system were calculated and used to explain oxidation process of the ce-la alloys. The fluorite phase is the unique oxidation products for most of the ce-la alloys.

关键词： ce-la alloy phase diagram thermodynamics oxidation

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