Preparation And Photoluminescence Of New Type Pyrosilicate By Gel-combustion Method Assisted By Microwave

In recent years, white LEDs was widely used in LCD screen, auto lamp, the landscapelighting and other emerging areas, because of non-toxic, small size, high efficiency,energysaving, long service life and environment friendly characteristics and so on, the improvementof white LEDs also become the focus of researchers.A new series of white LEDs pyrosilicate rare-earth luminescent materials for whiteLEDs were synthesized by gel-combustion method assisted by microwave. This method hasmany advantages, such as uniform composition, low synthesis temperature, simple operation,small particle size, grinding easily, and the time for the formation of gel and dry was greatlyshortened under the microwave inspire. It provides a new idea for saving energy and reducingenergy consumption.1. Eu³⁺activated Sr₂MgSi₂O₇red emitting phosphors were synthesized bygel-combustion method assisted by microwave. The phosphors possess hexagonal crystalstructure for magnesium yellow feldspar structure. The excitation spectrum ofSr₂MgSi₂O₇:Eu³⁺is composed of two major parts: one is the broad band between200and300nm, which belongs to the charge transfer of Eu³⁺-O²-; the other consists of a series of sharplines between300nm and450nm, ascribed to the f-f transition of Eu³⁺, and the strongestsharp peak is at395nm. The emission spectrum consists of two emission peaks at593nm and616nm, which is attributed to⁵D₀�'⁷F₁and⁵D₀�'⁷F₂of Eu³⁺respectively. The concentrationof Eu³⁺（x） has great effect on the emission intensity of Sr2-xMgSi2O7:Eu³⁺x. When x varies inthe range of0.02⁰.14, the intensity of emission peaks at593nm and616nm increases withthe concentration of Eu³⁺gradually. It is interesting that no concentration quenching occurs.2. High-brightness red emitting phosphors Sr₂MgSi₂O₇:Eu³⁺, M were synthesizedsuccessfully by doping different charge compensation agent and sensitizer by gel-combustionmethod assisted by Microwave. With the change of doping concentration of chargecompensators M （M=Li⁺、Na+、K+）, all the intensity of emission peaks of Sr₂MgSi₂O₇:Eu³⁺show the same trend of increasing first and then decreasing. When the doping concentration is8mol%, the intensity of emission peaks is the strongest, and the emission intensity at616nmis about1.97、1.68and1.63times of single-doped Eu³⁺sample respectively for Li⁺、Na+、andK+doping. The doping of sensitizer M (M=Zr⁴⁺, Gd³⁺) can also all improve the luminescent intensity of sample. With the change of doping concentration, the intensity of emission peaksof Sr₂MgSi₂O₇:Eu³⁺also show the trend of increasing first and then decreasing The optimumdoping concentration is4mol%and6mol%, respectively. Gd³⁺ions have the bettersensitization effect.3. A series of green phosphors Sr₂ZnSi₂O₇: Mn²⁺were synthesized by gel-combustionmethod assisted by microwave. The phase structure and luminescence properties ofas-synthesized phosphors were investigated by the X-ray diffraction and Fluorescencespectrophotometer respectively. The results show that Sr₂ZnSi₂O₇: Mn²⁺green phosphorshave the same tetragonal crystal structure as that of Sr₂ZnSi₂O₇. The excitation spectra havetwo strong peaks at262nm and420nm, which are ascribed to the⁶A₁-⁴T₁and⁶A₁-⁴Gtransitions of Mn²⁺respectively. The emission spectrum is also broad band, and the strongestemission peak is at523nm, which is attributed to⁴T₁�'⁶A₁transition of Mn²⁺. Theconcentration of Mn²⁺（x） has great effect on the emission intensity of Sr₂ZnSi₂O₇: Mn²⁺.When x varies in the range of0.001⁰.014, the intensity of emission peaks at523nmincreases with the concentration of Mn²⁺. The luminescence intensity reaches the strongestwhen the mole fraction of doped Mn²⁺is0.010. It is found that the doping of Ho³⁺cansensitize the luminescent intensity of Sr₂ZnSi₂O₇: Mn²⁺, while the doping of Er3+can notimprove it effectively, and the luminescent intensity will decrease obviously when the dopingamount is more than1mol%.