Effect of Sintering Temperature, Sm3+ Concentration and Excitation Wavelength on Luminescence Properties in Eu3+ Doped Strontium Tungstate Phosphors
Keywords:strontium tungstate, phosphors, color-tunable, warm white light emitting diodes
The color-tunable SrWO4:0.20Eu3+, Sm3+ phosphors are successfully prepared by co-precipitation method at a low temperature (800 °C). These phosphors can be efficiently excited by near-ultraviolet and blue light. The phase formation, luminescence properties, energy transfer between Eu3+ and Sm3+, and the critical distance were studied. The Sm3+ ions as the sensitizer could extend the excitation spectrum and enhance emission. The CIE chromaticity coordinate was also presented. The emission hues covered the regions from pink, orange, to reddish-orange, and eventually to red, which can be controlled by adjusting excitation energy, calcination temperature, and doping rare earth ions ratio via the energy transfer. The high efficiency and high color purity red emitting SrWO4:0.20Eu3+, xSm3+ (x = 0.005 ¸ 0.01) phosphors have higher color saturation than the commercially available Y2O2S:Eu3+ red phosphor, which is in coincidence with the National Television Standard Committee system standard for red chromaticity (0.67, 0.33). The obtained phosphors exhibit an excellent light emitting efficiency, color-purity and lower correlated color temperature of the comfortable warm white LEDs.
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