Characteristics and synthesis mechanism of Gd2O2S:Tb phosphors prepared by vacuum firing method

Abstract

Characteristics and synthesis mechanism of Gd2O2S:Tb phosphors prepared by vacuum firing were investigated by photoluminescence (PL) spectra, X-ray diffraction (XRD), scanning electronic microscopy (SEM) and transmission electron microscopy (TEM). The mixtures of raw materials were tested by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The firing temperature was reduced to about 725 °C by the vacuum firing method. The particle size decreased. Meanwhile the particle size distribution and morphology were improved and the luminescence of Gd2O2S:Tb phosphors was also enhanced as the degree of vacuum decreases. With the decrease of the degree of vacuum, the intensity of the excitation spectrum was strengthened and the band was widened being the particle size of the host lattice decreased to nano scales. The peak with high intensity around 272 nm in the excitation spectra (λEm = 545 nm) of Gd2O2S:Tb nanophosphor may be attributed to the 4d–5f transitions of Gd atoms, which may play a significant role in the energy transfer between Tb3+ and Gd3+ ions.5D4–7FJ transitions of Tb3+ ion were mainly concentrated in the narrow green emission spectrum (535–555 nm) with its sharp peak at 545 nm. The synthesis mechanism of Gd2O2S:Tb phosphors prepared by vacuum firing was also studied.