Abstract:

Red phosphors Sr(1-1.5x)Mo0.8Si0.2O3.8∶Eu3+x(x=0.1, 0.2, 0.3, 0.4, 0.5) used for LED were synthesized by high temperature solid state method. XRD, fluorescence excitation and emission spectra were used for analysis the phase composition and luminescent properties of the materials. The XRD result of sample x=0.1 is consistent with JCPDSCard No.08-0482(SrMoO4), the lattice constant of materials are a=0.5390 nm, b=0.5390 nm and c=1.1998 nm which is belongs to I41/a space group. As luminescence center, Eu3+ takes the position of Sr2+. With the increase of Eu3+ concentration, which represents the concentration of Eu3+, the emission intensities of 5D0-7F1 magnetic dipole transition at 593 nm and 5D0-7F2 transition at 614 nm were converted. When x≤0.4, the magnetic dipole transition 5D0-7F1 dominates emitting with an orange light. For x=0.5, the electric dipole transition 5D0-7F2 dominates emitting with red light. The excessive doped Eu3+ ion in the lattice could not enter into SrMoO4 site, but only exist in lattice vacancy formed defect, which made Eu3+ in unsymmetrical lattice site. It is lead to promote the electric dipole 5D0-7F2 transitions and reduce the magnetic dipole 5D0-7F1 transitions. Therefore, phosphors with different emitting color can be obtained by adjusting the content of activator. In Eu3+ doped strontium silicon molybdate system, under excitation at 614 nm, the wide bands at 368 nm and the absorption band at 467 nm corresponded to absorption of the host matrix and the 7F0-5D2 transitions, respectively. The extra activator Eu3+ at lattice gap(x=0.5) promote the absorption bands 3 times more than that for x=0.4. The material can produce tunable orange-red color, and its excitation wavelength can match with UV LED chips very well.

Key words: White light LED, SrMo0.8Si0.2O4:Eu3+x, Luminescence properties