SYNTHESIS AND PHOTOLUMINESCENCE PROPERTIES OF ELLIPSOIDAL La2O2SO4:Eu3+ PHOSPHORS

This research was focused on the homogeneous precipitation synthesis of a series of Eu3+ ion-activated ellipsoidal La2O2SO4 phosphors based on the La2(SO4)3-CO(NH2)2 reaction system. The structural identification, thermal analysis, morphology and luminescence properties of the as-prepared products were characterized with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG/DSC), field emission scanning electron microscopy (FESEM) and photoluminescence (PL) spectra. Pure La2O2SO4 ellipsoidal particles with a long radius of about 2 µm and a short radius of about 1 µm were successfully prepared by calcining a rhombus-like precursor at 800 °C for 2 h in air. The formation mechanism of the precursor and its corresponding calcination product were also proposed. Photoluminescence results revealed that the strongest red emission peak was centered at 619 nm upon 249-nm ultraviolet (UV) light excitation in La2O2SO4:x%Eu3+ (x = 3, 6, 9, 12 and 15) phosphors. The exchange interaction was responsible for the concentration quenching mechanism of the 5D0→7F2 transition of Eu3+ ions in the La2O2SO4 host lattice. The optimal x value was 15 and the corresponding decay process showed a single exponential decay behavior whose lifetime t and color correlation temperature (CCT) were calculated to be 2.112 ms and 2752 K, respectively.