Co-precipitation synthesis of neodymium-doped yttrium aluminium oxides nanopowders: quantitative phase investigation as a function of joint isothermal treatment conditions and neodymium content.

Abstract

Neodymium-doped yttrium aluminium nanopowders with nominal Nd:Y:Al ratio equal to X:3-X:5 (where X = 0, 0.006, 0.012, 0.024, 0.048, 0.081, 0.096, 0.171, 0.192, 0.384, 0.540 and 0.720) were prepared by the co-precipitation method and subjected to five cumulative stages of isothermal treatment in the temperature range from 900 to 1050 °C. The phase evolution of the oxides were investigated quantitatively by the X-ray powder diffraction approach using the Rietveld method of analysis. An almost single phase cubic garnet structure was attained at temperatures as low as 900 °C for specimens with neodymium loading less than ca. 6 at.% with respect to total (Nd + Y) atoms. Isothermal treatments of the powders up to 1050 °C remove the hexagonal YAlO3 metastable phase and maximize the amount of the garnet phase. However, for neodymium loading higher than ca. 6 at.%, the garnet structure remains substantially affected by the presence of monoclinic Y4Al2O9 and orthorhombic distorted perovskite-like YAlO3 phases.