The phase relationships of the ternary system Eu 2 O 3 - La 2 O 3 - ZrO 2 and binary Eu 2 O 3 - La 2 O 3 subsystem were experimentally and thermodynamically studied. Six three-phase fields and nine two-phase ones in the Eu 2 O 3 - La 2 O 3 - ZrO 2 system were investigated by X-ray diffraction, scanning electron microscopy and electron probe microanalysis with wavelength dispersive spectrometer at 1873 K and 1673 K. Nevertheless, there only existed a two-phase region in the Eu 2 O 3 - La 2 O 3 system in the temperature range from 1873 K to 1673 K. After that, the ternary mixing parameters for the system Eu 2 O 3 - La 2 O 3 - ZrO 2 including the binary interaction parameters in the Eu 2 O 3 - La 2 O 3 subsystem are optimized with the CALPHAD (CALculation of PHAse Diagrams) method, based on obtained experimental results. The high-temperature phase relationships and the special type of continuous solid solutions (La 2-x Eu x Zr 2 O 7 ) investigated in present work will contribute to exploring new materials with specific properties such as optical transparency.
Xin Zhao,Yishuai Jing,Zhonghua Dai,Yuanbo Chu,Zhenyu Liu,Yu Cong,Jiaming Song
As a wide-bandgap rare-earth oxide, Eu2O3 was often utilized as an auxiliary material of other photocatalysts because its photocatalytic performance was limited by the luminescence characteristics of Eu3+ and low light utilization. In this study, we improved the photocatalytic degradation performance of the Eu2O3 nanoparticles by doping with Fe cations. The Eu2O3 nanoparticles with different Fe-doping concentrations (1, 3, and 5%, noted as EF1.0, EF3.0, and EF5.0, respectively) were synthesized via chemical precipitation and calcination methods. It was found that doping could reduce Eu2O3’s bandgap, which probably originated from the introduction of oxygen vacancies with lower energy levels than the conduction band of Eu2O3. Compared with the undoped Eu2O3 nanoparticles with a removal efficiency of 22% for degrading rhodamine B dye within 60 min, the photocatalytic degradation efficiencies of EF1.0, EF3.0, and EF5.0 were demonstrated to be improved to 42, 48, and 33%, respectively, and EF3.0’s performance was the best. The enhanced photocatalytic performance of the doped samples was related to the oxygen vacancies acting as capture centers for electrons, such that the photogenerated electron–hole pairs were efficiently separated and the redox reactions on the surface of the nanoparticles were enhanced accordingly. Additionally, the enhanced light absorption and broadened spectral band further improved EF3.0’s degradation efficiency.
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