Microwave synthesis of Y₂O₃:Eu³⁺ nanophosphors: A study on the influence of dopant concentration and calcination temperature on structural and photoluminescence properties

Red fluorescent emitting monodispersed spherical Y₂O₃ nanophosphors with different Eu³⁺ doping concentrations (0–13 mol%) are synthesized by a novel microwave assisted urea precipitation, which is recognized as a green, fast and reproducible synthesis method. The effect of Eu³⁺ doping and calcination temperature on the structural characteristics and luminescence properties of particles is investigated in detail. The as prepared powders have (Y,Eu)(OH)(CO₃) structure which converts to Y₂O₃:Eu³⁺ from 500 °C and become crystalline at higher temperatures. The crystallite size of nanophosphors increased from 15 nm to 25 nm as the calcination temperature increased from 700 °C to 1050 °C. The efficient incorporation of Eu³⁺ ions in cubic Y₂O₃ host matrix is confirmed by the calculated X-ray Powder diffraction (XRPD) structural parameters. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs show that the as obtained and calcined particles are spherical, monodispersed and non-agglomerated. The overall size of particles increases from 61±8 nm to 86±9 nm by increasing Eu³⁺ concentration from 0 mol% to 13 mol%. High resolution TEM revealed polycrystalline nature of calcined particles. The particles exhibit a strong red emission under ultraviolet (UV) excitation. The photoluminescence (PL) intensity of the peaks increases proportionally with Eu³⁺ concentration and the calcination temperature with no luminescence quenching phenomenon observed even for Y₂O₃:13%Eu³⁺. The fluorescent emission properties combined with the monodispersity and narrow size distribution characteristics make the Y₂O₃:Eu³⁺ heavy metal free nanophosphors applicable in fluorescence cell imaging and as fluorescence biolabels. - Highlights: • Microwave assisted precipitation method for fabrication of Y₂O₃:Eu³⁺ nanophosphors. • Energy efficient, fast, surfactant and hazardous precursors free synthesis. • Chemically homogeneous, monodispersed spherical red emitting nanophosphors. • High crystallinity at elevated calcination temp. leads to increased PL intensity. • Absence of quenching at high Eu³⁺ concentration – up to 13 mol%.