Lin Gan,Fang-Fang Xu,Xiong-Hui Zeng,Zuo-Sheng Li,Zhi-Yong Mao,Ping Lu,Ying-Chun Zhu,Xue-Jian Liu,Lin-Lin Zhang
The critical doping structures of rare-earth atoms in the promising β-SiAlON phosphors have long been argued owing to the lack of direct evidence. Here, the exact locations and coordination of the Ce rare-earth atoms in the β-SiAlON structure have been examined using an atom-resolved Cs-corrected scanning transmission electron microscope. Three different occupation sites for the Ce atoms have been directly observed: two of them are in the structural channel coordinated with six and nine N(O) atoms, respectively; the other one is the unexpected substitution site for Si(Al). The chemical valences and stabilities of the doping Ce ions at the different occupation sites have been evaluated using density functional calculations. Correlation of the different doping structures with the luminescence properties has been investigated by the aid of cathodoluminescence (CL) microanalysis, which verifies the different contribution of the interstitial trivalent Ce ions to the light emission while no luminescence is observed for the substitutional doping of quadrivalent Ce.
Wei Xie,Qiangang Fu,Chunyu Cheng,Pei Zhang,Ningning Yan
The medium-entropy oxide (Y 1/3 Yb 1/3 Lu 1/3 ) 2 O 3 with a body-centered cubic structure was successfully synthesized by solid-state reaction process, and then it was introduced into SiC ceramic to study its effect on the oxidation behavior of SiC ceramic at 1700 °C. The (Y 1/3 Yb 1/3 Lu 1/3 ) 2 O 3 -modified SiC ceramic exhibited better oxidation resistance than its individual oxides (Y 2 O 3 , Yb 2 O 3 , and Lu 2 O 3 ) modified SiC ceramic. The experimental and calculated results all indicate that the rare-earth atoms had the tendency to diffuse into the SiO 2 structure and occupy the interstitial positions within SiO 2 structure. The introduction of medium-entropy oxide (Y 1/3 Yb 1/3 Lu 1/3 ) 2 O 3 reduced the initial oxidation rate of the ceramic samples (1−3 h), and enhanced the stability of SiO 2 structure, thus resulting in a better oxidation resistance at 1700 °C.
危险品化学品经营许可证（带存储）