Hydrothermal synthesis and photoluminescence properties of Gd2O2SO4:Eu3 + spherical phosphor

• A hydrothermal routine for synthesizing Gd2O2SO4:Eu3 + phosphor
• No releasing toxic sulfur trioxide in the synthesis process
• Pure spherical Gd2O2SO4:Eu3 + particle with narrow size distribution
• High packing densities and high luminescence intensity

Gd2O2SO4:Eu3 + spherical phosphor was successfully synthesized through a simple hydrothermal synthesis routine from commercially available Gd2(SO4)3·8H2O, Eu2(SO4)3·8H2O and urea as the starting materials. The as-synthesized products were characterized by XRD, SEM, FT-IR, DTA–TG–DTG and photoluminescence (PL) spectra. It is found that the phase and morphologies of the precursors are strongly dependent on m value, namely, the molar ratio of urea to Gd2(SO4)3. The optimal m value is 2. DTA–TG–DTG, FT-IR and XRD analyses show that the optimal precursor is composed of amorphous Gd2(OH)2CO3SO4·H2O phase and can be converted into pure Gd2O2SO4 phase at a temperature higher than 800 °C for 2 h in air. SEM observation shows that the pure Gd2O2SO4 phosphor particles are spherical in shape and well dispersed, with a particle size range of about 1–3 μm. PL spectra reveal that the strongest emission peak for Gd2O2SO4:Eu3 + spherical phosphor is located at 620 nm under 270 nm light excitation, which corresponds to the 5D0 → 7F2 transition of Eu3 + ions. The quenching concentration of Eu3 + ions is 15 mol% and the concentration quenching mechanism is the exchange interaction for the 5D0 → 7F2 transition of Eu3 + ions.

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