Rare earth sulfides were systematically synthesized via the sulfurization of their commercial oxide powders using CS2 gas to shorten sulfurization time, and their UV-vis absorption spectra were investigated. The appropriate sulfurization conditions were studied. For the rare earth sulfides with the same crystal structure, the sulfurization temperature showed increasing tendency with the decrease of rare earth element atomic radii. The UV-vis absorption spectra of rare earth sulfides did not depend on the crystal structure of rare earth sulfides, but on the 4f electronic structure of rare earth element. The data showed that the optical band gaps of rare earth sulfides were irregular, and the values ranged from 1.65 to 3.75 eV.
The new phosphors Bi2ZnB2O7:Ln3+ (Ln3+=Eu3+,Dy3+) were synthesized by solid-state reaction technique.The obtained phosphors were investigated by means of X-ray powder diffraction (XRD),photoluminescence excitation and emission spectra with the aim of enhancing the fundamental knowledge about the luminescent properties of Eu3+ and Dy3+ ions in the Bi2ZnB2O7 host lattice.XRD analysis shows that all these compounds are of a single phase of Bi2ZnB2O7.The excitation and emission spectra of Bi2ZnB2O7:Ln3+ (Ln3+=Eu3+,Dy3+) at room temperature show the typical 4f-4f transitions of Eu3+ and Dy3+,respectively.The hypersensitive transitions of 5D0→7F2 (Eu3+) and 4F9/2→6H13/2 (Dy3+) are relatively higher than those of the insensitive transitions in Bi2ZnB2O7.It is conceivable that the Bi2ZnB2O7 structure provides asymmetry sites for activators (Eu3+,Dy3+).The optimum concentrations of Eu3+ and Dy3+ ions in Bi2ZnB2O7 phosphors are both x=0.05.
In order to investigate the suitability of ternary rare earth sulfide LanCe2 xS3 in plastic application as a red pigment, we prepared LaxCe2 xS3 via the sulfurization of the oxide powders using CS2 gas. In the sulfurization of LaxCe2_xS3, β-phase and y-phase ter- nary rare earth sulfide LaxCe2_xS3 were synthesized at the sulfufization temperature of 1000 and 1250 ℃ for 3 h, respectively. The UV-vis absorption spectra of synthesized LaxCe2_xS3 showed that the absorption wavelengths of 13-phase and y-phase LaxCe2_xS3 samies were in the region of 617-70 nm and 607-53 nm, respectively. They were in red absorption region. Furthermore, the scanning electron microscopy （SEM） results of the synthesized LaxCe2-S3 samples were investigated. The typical SEM microgmphs indicated that the particle sizes of synthesized LaxCe2 xS3 were in the range of 0.5-5 μm.
