Abstract
The synthesis and photoluminescent properties of BaLa4(WO4)7 doped with various rare earth ions such as Eu3+、Sm3+、Dy3+、Tb3+、Er3+ ions and introduced Sr2+ ions to substitute the Ba2+ ions or Mo6+ ions to substitute the W6+ ion had been investigated. For BaLa4-xEux(WO4)7 phosphors, the emission intensity of 5D0 →7F2 transition was stronger than 5D0→7F1 transition. The emission intensity increased with Eu3+ concentration until x = 0.24, and then decreased. As the Eu3+ concentration was further raised to x = 0.28, the second phase BaWO4 and La2(WO4)3 appeared. In order to further enhance the optical properties, we introduced Sr2+ to substitute Ba2+ or Mo6+ to substitute W6+ in the BaLa4-xEux(WO4)7 compound. The results showed that increasing the Sr2+ or Mo6+ content could increase the solubility of Eu3+ in BaLa4-xEux(WO4)7, and therefore enhanced the emission intensity. Ba0.7Sr0.3La3.2Eu0.8(WO4)7 and BaLa3.4Eu0.6(W0.8Mo0.2O4)7 had optimal doping concentration and maximum intensity, and the CIE chromaticity coordinate located at（0.657,0.342）、（0.655, 0.341） very close to the NTSC system standard red chromaticity（0.67, 0.33）. The chromaticity coordinate of BaLa4(WO4)7 : Tb3+ phosphors varied with the Tb3+-doped concentrations from blue to green, showed that BaLa4(WO4)7 : Tb3+ phosphors were color-tunable. BaLa4(WO4)7 doped with various activators（Sm3+、Dy3+、Er3+ ions）could emit different colors. such as orange （Sm3+）、yellowish white （Dy3+）、green（Er3+）. One of the interesting results of this that the excitation wavelength of the phosphors and the emission wavelengths of the LED (350~480 nm) have closely overlapped, which provides the potential as the LED converted phosphors in solid state lighting technology.
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