Reduction, Luminescence And Microstructure Of Sm²⁺ Doped NaSr_1-xBa_xPO₄

Rare-earth doped light-emitting material has been paid intense attention because it has been widely used in various fields, such as in display devices, laser and display. Sm²⁺ ion has potential application in high-density optical storage because of its property of persistent spectral hole burning. Eu³⁺ as activating ions has been the most widely used in the field of luminescence and display. Sm²⁺ and Eu³⁺ ions are also two good kinds of probe material. It highly affected on the spectra and decay. Take advantage of this feature, we can study the surrounding environment of Sm²⁺ and Eu³⁺ ions which provides the symmetry of different luminescence centers in the matrix and then gives details of physical structures.This paper chose the orthophosphate as a substrate material, Sm³⁺ and Eu³⁺ as activating ions, Sm³⁺ and Eu³⁺ ions doped strontium barium phosphate sodalite (NaSr_1-xBa_xPO₄). Sm²⁺ ion was reduced by X-ray irradiation in strontium barium phosphate sodalite and KSrPO₄. We studied the luminescence of Sm²⁺ and Eu³⁺ ions and discussed the relationgship between defect and luminescence.In the chapter three, the effect of different mole ratios of Sr/Ba on the crystal structure, the reduction of Sm²⁺ and the luminescence of Sm²⁺ in NaSr_1-xBa_xPO₄ were also discussed; we studied the crystal field environment of RE ions in NaSr_1-xBa_xPO₄ through the analysis of the fluorescence spectra. The results show that with increasing of Ba atoms the crystallography parameters and the volume of cell in NaSr_1-xBa_xPO₄ is increased and the main XRD peaks shift to low degree, the reductive efficiencies of Sm²⁺ ions in NaSr_1-xBa_xPO₄ are enhanced, while the corresponding decay time of 5D0→7F0 transition decreases rapidly. The structure of Sm²⁺ in NaSr_1-xBa_xPO₄ is a heavily disturbed crystalline environment due to the Sr(Ba) disorder and the complicated defects in the lattice created by the X-ray irradiation.In the chapter four, we discussed the fluorescence spectra of Sm²⁺-doped KSrPO₄, crystallographic position of Sm²⁺ ions and the temperature effects on the fluorescence. It was found that there were three crystallographic cationic sites available for Sm²⁺. Fluorescence spectra of Sm²⁺ ions is made up of the emission lines (688-715 nm) and the broad emission bands of 650–800 nm. The emission lines came from the 5D0→7FJ (J=0,1,2) transitions of Sm²⁺ ions. The broad emission bands are referred to the 5d→4f transition of Sm²⁺ ions. The 5D0→7F0 transitions of Sm²⁺ ions are broad which proves the structure of Sm²⁺ doped KSrPO₄ is a heavily disturbed crystalline environment due to the Sr/K disorder and the complicated substitutions among K, Sr and Sm²⁺ ions. These results can be helpful for the luminescence and application of the other RE ions in KSrPO₄. Since the ionic radii and the chemical properties for Sm²⁺ and Eu²⁺ are nearly identical, one may expect the crystallographic position and luminescence of Eu²⁺ in KSrPO₄.In the chapter five, characteristics of Eu³⁺-doped NaSr_1-xBa_xPO₄ were investigated by the use of XRD, SEM, FTIR and FT-IRaman spectra. The effect of different mole ratios of Sr/Ba on the crystal structure was also discussed. The excitation and emission spectra of Eu³⁺-doped NaSr_1-xBa_xPO₄ were discussed. The results show that NaSr_1-xBa_xPO₄ belongs to hexagon system, all the vibrations were from PO₄3? anion unit, the Eu³⁺ ion in crystal was located in non-reversion center in the lattice, the crystallographic site of cation in the crystal is highly disturbed and disordered. The decay exhibit a single exponential curve indecated that there is only one Eu³⁺ luminescence center. With the barium content increasing, luminous intensity ratio of 5D0→7F2 and 5D0→7F1 of Eu³⁺ ion increased significantly which indicated that Eu³⁺ ions in the crystal lattice symmetry decresed significantly. The high ratio is useful to the luminous intensity and color of the doped material.The novelties of this desertation are the following: we successfully achieved the reduction of Sm²⁺ in the NaSr_1-xBa_xPO₄ by X-ray irradiation. The microstructure of the RE ions doped NaSr_1-xBa_xPO₄, X-ray irradiation time and the content of Ba effect on the reduction efficiency of Sm²⁺ were first reported. Besides this, we also discussed the structural features of Sm²⁺-doped KSrPO₄, crystallographic position of Sm²⁺ ions in KSrPO₄ and the temperature effects on the fluorescence. These results are helpful in further research of NaSr_1-xBa_xPO₄ and KSrPO₄. And this also are good references for the reduction of rare-earth ions.