"XAFS study of Zr local environment in amorphous precursors of La2Zr2O7 ceramics prepared by a nitrate-modified alkoxide synthesis route
published: Feb. 12, 2008, recorded: October 2007, views: 6257
Report a problem or upload filesIf you have found a problem with this lecture or would like to send us extra material, articles, exercises, etc., please use our ticket system to describe your request and upload the data.
Enter your e-mail into the 'Cc' field, and we will keep you updated with your request's status.
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.
Download slides: slonano07_ion_xsz.ppt (3.3 MB)
Link this pageWould you like to put a link to this lecture on your homepage?
Go ahead! Copy the HTML snippet !
Reviews and comments:
Hello Ms Elena Ion
I am portuguese and i would like to congratulate your presentation about the work on "XAFS study of Zr local environment in amorphous precursors of La2Zr2O7 ceramics prepared by a nitrate-modified alkoxide synthesis route".
I am doing my master thesis about "Ceramic powders preparation of Lanthanum zirconate" and I wonder if you can provide some information about this theme.
Write your own review or comment: