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“通过硝酸盐改性的醇盐合成路线制备的La2Zr2O7陶瓷无定形前体中Zr局部环境的XAFS研究"XAFS study of Zr local environment in amorphous precursors of La2Zr2O7 ceramics prepared by a nitrate-modified alkoxide synthesis route |
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| 课程网址: | http://videolectures.net/slonano07_ion_xsz/ |
| 主讲教师: | Elena Ion |
| 开课单位: | 约瑟夫·斯特凡学院 |
| 开课时间: | 2008-02-12 |
| 课程语种: | 英语 |
| 中文简介: |  |
| 课程简介: | We prepared La2Zr2O7 by the nitrate-modified alkoxide-based sol-gel synthesis route. The dehydrated lanthanum nitrate was mixed with zirconium n-butoxide in 2-methoxyethanol and refluxed for 3 h. The obtained liquid was slowly dried. At 150oC, the sample self-ignited. According to XRD, the powder was amorphous upon heating up to 700oC and crystallization took place at 800oC. The powder was composed of friable agglomerates of about 70 nm sized nano-particles. By EXAFS analysis we investigated the Zr and La local environment upon transition from the sol to the amorphous powder in order to learn about the distribution of the constituent metal atoms at the sub-nanometer level. We observed that the Zr EXAFS spectra of the sol and the precursor powder dried at 150 oC and heated at 500 oC were similar, indicating that the local environment of Zr atoms was not affected during the liquid-amorphous solid transition, Zr – O – Zr links were formed already in the sol and preserved even in the powder heated at 500 oC. No La – O – Zr links in the sol or in the amorphous powder were observed. The La EXAFS spectrum of the LZ sol is similar to the spectrum of dehydrated lanthanum nitrate (LN sol), while in the spectra of dried and heated powder, vanishing of the second peak was noticed. No La-La or La-Zr corelation could be established. Since no link, between La and Zr species, was confirmed in the early stages of the synthesis, the reaction between the species proceeded as a solid-state reaction when long range diffusion became available leading to the pure pyrochlore phase. The proposed synthesis route, allowed a very good mixing of the species at the nanometre level. |
| 关 键 词: | 硝酸盐; 路线; 光谱 |
| 课程来源: | 视频讲座网 |
| 最后编审: | 2019-09-28：yuh |
| 阅读次数: | 53 |