FSAEI HE North-Caucasus Federal University, Stavropol, Russia
S. N. Kichuk, Senior Researcher at the Department of Science, e-mail: skichuk@ncfu.ru
I. S. Chikulina, Senior Researcher at the Department of Science, e-mail: ichikulina@ncfu.ru
D. S. Vakalov, Head of the Sector of Physico-Chemical Research and Analysis Techniques, Candidate of Physical and Mathematical Sciences, e-mail: dvakalov@ncfu.ru

The paper presents a method for the synthesis of spherical gadolinium oxide powders and the results of a study of the obtained samples characteristics. Gadolinium oxide powders were obtained by calcination in air at a temperature of 1000 ^оC of gadolinium hydroxycarbonate previously synthesized by chemical precipitation. The synthesis was carried out at different molar concentrations of the precipitated gadolinium nitrate solution (Gd(NO₃)₃· 6H₂O) 0.02; 0.03; 0.034; 0.041; 0.047 mol/l and constant concentration of the precipitator – carbonic acid diamide (CO(NH₂)₂) (carbamide) 0.5 mol/l. Experimental samples of gadolinium oxide powders were obtained and their properties were studied. The phase composition was determined by X-ray phase analysis, and micrographs of the surface of gadolinium oxide powder were obtained by scanning electron microscopy. The influence of gadolinium hydroxycarbonate synthesis conditions on the morphology of gadolinium oxide powder obtained on its basis, in particular the pH and concentration of the precipitated solution, has been studied. It was determined that the synthesis of gadolinium hydroxycarbonate from dilute solutions (0.02 mol/l) contributes to the production of monodisperse gadolinium oxide powders consisting of microspheres of the order of 200 nm in size formed by nanocrystallites up to 40 nm in diameter. The optimal technological conditions are presented to facilitate the production of gadolinium oxide powder with specified properties and a yield of up to 90% of the calculated values. The pH value during precipitation of gadolinium hydroxycarbonate should be controlled and maintained throughout the synthesis within the values of 7–7.5. The factors influencing the technological losses and the yield of gadolinium oxide powder are determined.
The work was performed using the equipment of the Center for the Collective Use of the North-Caucasus Federal University.

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