Direct synthesis of Neodymium doped Yttrium Oxide nanopowders by mixed fuel microwave gel combustion process

Microwave assisted direct synthesis of phase pure, single phase cubic Nd:Y2O3 nanopowder by using a mixture of fuels — urea and L-alanine, without additional calcination is being reported for the first time. Solutions of metal nitrates and fuel mixture of urea and L-alanine in ratio of 1:1.25:0.5 respectively were gelled and subsequently combusted in microwave. Effect of sulfate ion on particle morphology was also investigated with addition of 5 mol% ammonium sulfate with respect to metal cation. Microwave combustion resulted in formation of fully crystalline, phase pure Nd:Y2O3 nanopowder for both the reaction mixture as observed by XRD. TGA of microwave combusted powders showed ~ 10–17% total wt loss indicating maximum burning of organics during combustion step itself. Particles in size range ~ 40–150 nm obtained which further reduced to ~ 25 nm on sulfate addition and gave ~ spherical morphology in both the cases as shown by TEM. However with urea and L-alanine individual fuels microwave combusted powders were required to be calcined at 1000 °C for 3 h in oxygen flow to obtain phase pure cubic Nd:Y2O3. Thus mixture of fuels led to highly exothermic combustion reaction leading to formation of phase pure single phase cubic yttria without calcinations. Further microwave radiation led to volumetric heating leading to formation of fine particles of uniform morphology.

Mixed fuel microwave combustion gave phase pure Nd:Y2O3 directly. Close to spherical particles in size range ~ 45–150 nm (A) reduced to ~ 25 nm (b) on sulfate addition as shown by TEM below. Mixed fuel gave exothermic reaction thus preventing the need for calcinations and volumetric heating by microwave led to uniform morphology.Figure optionsDownload as PowerPoint slideHighlights
► Mixed fuel combustion gave direct synthesis of Nd:Y2O3.
► Microwave combustion was, rapid and uniform.
► Achieved close to spherical, ~ 25 nm size on sulfate addition.