Abstract:
The structural states of Gd$_2$O$_3$ and Gd$_2$O$_3$ : 2% Eu$^{3+}$ synthesized by the glycine-nitrate method were studied. As a result of this synthesis, in addition to the known cubic modification of gadolinium oxide, two new previously unknown phases are formed. The first phase is formed during prolonged exposure at room temperature of the initial nanocrystalline cubic structure obtained at a synthesis temperature of 650$^\circ$C. The second phase has orthorhombic syngony and is formed during either long-term synthesis at a temperature of 650$^\circ$C, or short-term syntheses at a higher temperature. Both phases pass into the traditional cubic modification during further high-temperature annealing. In addition, the effect of structural “infection” was found, which consists in the fact that during annealing of the cubic phase of Gd$_2$O$_3$ doped with Eu$^{3+}$ ions in the range of 800–1100$^\circ$C, its partial transition into the monoclinic phase occurs, which disappears with a further increase in the annealing temperature.
Keywords:synthesis of Gd$_2$O$_3$, glycine-nitrate method, nanocrystalline state, X-ray diffraction research methods, phase transitions.
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