Highly sinter-active nanocrystalline RE₂O₃ (RE = Gd, Eu, Dy) by a combustion process, and role of oxidant-to-fuel ratio in preparing their different crystallographic modifications

Abstract

Highly sinter-active powders of RE2O3 [rare earth (RE) = Gd, Eu, Dy] have been prepared using the corresponding metal nitrates as the oxidants, and glycine and citric acid as the fuels. Two different oxidant-to-fuel ratios, namely stoichiometric ratio and fuel-deficient ratio were used to explore the possibility of preparing different crystallographic modifications. By a careful control of oxidant-to-fuel ratio, nanocrystalline Eu2O3 and Gd2O3 could be prepared in cubic (C-type) as well as monoclinic (B-type) modifications. However, the high-temperature monoclinic modification could not be obtained for Dy2O3 due to a very high C-to-B-type phase transition temperature. The crystallite size, surface area, and sintering behavior were also studied for powders prepared using different oxidant-to-fuel ratios, and the results showed a remarkable correlation between different fuel contents and powder properties. Some of these powders resulted in pellets of nearly theoretical density. The sintered microstructure was studied by scanning electron microscopy.

Glycine–Nitrate Process for the Elaboration of Eu3+‐Doped Gd2O3 Bimodal Nanoparticles for Biomedical Applications

“…The Lorentzian shape of the diffraction peaks and their full width at half-maximum (FWHM) values are consistent with nanometric crystallite sizes. Gd 2 O 3 undergoes a cubic to monoclinic structural transition at 1200°C, [58] and the heat provided by the reaction induces this polymorphic transition.…”

Synthesis and Characterization of Nanocrystalline In2O3 and Its Efficacy as a Catalyst for the One Pot Synthesis of Amidoalkyl Naphthols

“…Gel-combustion synthesis [29][30][31] is a soft chemical route used to synthesize various nanocrystalline oxides. Stoichiometric proportion of indium nitrate (oxidant) and glycine (fuel), calculated on the basis of propellant chemistry [32] is used to synthesize indium oxide.…”

Combustion synthesis of lead oxide nanopowders for the preparation of PMN–PT transparent ceramics

“…The powder characteristics are dependent on the flame temperature generated during the combustion, which in turn is a function of the nature of fuel and of the fuel-to-oxidant ratio. The effects of different fuels and fuel-to-oxidant ratios on the crystallographic phases produced and powder characteristics have been extensively investigated by Chavan and Tyagi [31] and Bedekar et al [32] for many oxides. It was established that a careful control of the fuel-to-oxidant ratio is necessary to get the desired product [33].…”