@article{f732f8d520554220b1fee2d70b045209,
title = "Phase stability of rare earth sesquioxides with grain size controlled in the nanoscale",
abstract = " Rare earth oxides are important materials due to their chemical and physical properties. The rare earth sesquioxides (RESOXs) possess a cubic, monoclinic, or hexagonal structure, depending on pressure, temperature and ionic radius. When RESOXs take the form of single crystalline grains with diameter in the nanoscale range (nanocrystals), it is suspected that the grain size determines the phase stability as well. RESOXs with medium ionic radius such as Gd 2 O 3 , Eu 2 O 3 and Sm 2 O 3 in the low temperature range up to 900°C may take the monoclinic structure or the cubic structure, depending on the synthesis process. The structure determining factor can be, besides temperature, also the grain size. In order to determine the stable structure taking into account grain size as a parameter, we produced Gd 2 O 3 and Sm 2 O 3 nanocrystals embedded in a neutral MgO matrix. This way, we prevented grain growth during annealing. For comparison, we annealed pure Gd 2 O 3 and Sm 2 O 3 nanocrystals in which temperature increase caused grain growth, as in traditional experiments for phase stability determination. We have shown that for coarse grained materials at low temperature monoclinic is the stable structure. For nano-sized crystallites, cubic is the stable structure. This explains the controversial results as far as which phase is the stable one below 900°C and permits to program the needed structure by controlling crystallization kinetics and grain growth.",
keywords = "X-ray methods, nanomaterials, oxides, phase diagrams, rare earths",
author = "Giora Kimmel and Shneck, {Roni Z.} and Witold Lojkowski and Ze'ev Porat and Tadeusz Chudoba and Dmitry Mogilyanski and Stanislaw Gierlotka and Vladimir Ezersky and Jacob Zabicky",
note = "Funding Information: The authors are grateful to Alla Sahartov for drawing Figure 1A,B, to Evgeni Yonash for thermal treatments of Sm and Sm/Mg oxides, and to Einat Nativ‐Roth and Jan Mizeradzki for the HRSEM work. The work was in part supported from statutory funding of the Institute of High Pressure Physics, PAS. Research was carried out using equipment funded by the CePT project, reference: POIG.02.02.00‐14‐024/08, financed by the European Regional Development Fund within the Operational Programme “Innovative Economy” for 2007‐2013. GK is thankful for funding from ICDD (International Centre for Diffraction Data) ‐ Grant‐in‐aid project 96‐08 {"}Synthesis and Characterization of Multicomponent Rare Earts Oxides prepared by Sol‐Gel Technique{"}. Funding Information: The authors are grateful to Alla Sahartov for drawing Figure A,B, to Evgeni Yonash for thermal treatments of Sm and Sm/Mg oxides, and to Einat Nativ-Roth and Jan Mizeradzki for the HRSEM work. The work was in part supported from statutory funding of the Institute of High Pressure Physics, PAS. Research was carried out using equipment funded by the CePT project, reference: POIG.02.02.00-14-024/08, financed by the European Regional Development Fund within the Operational Programme ?Innovative Economy? for 2007-2013. GK is thankful for funding from ICDD (International Centre for Diffraction Data) - Grant-in-aid project 96-08 {"}Synthesis and Characterization of Multicomponent Rare Earts Oxides prepared by Sol-Gel Technique{"}. Publisher Copyright: {\textcopyright} 2019 The American Ceramic Society",
year = "2019",
month = jul,
day = "1",
doi = "10.1111/jace.16396",
language = "English",
volume = "102",
pages = "3829--3835",
journal = "Journal of the American Ceramic Society",
issn = "0002-7820",
publisher = "Wiley-Blackwell",
number = "7",
}