| White light emitting diode (WLED) is considered as the next-generation of solid-state lighting resource due to the characteristics of small volume, high energy efficiency, low power consumption, environment- friendly, long lifetime etc. Nowadays, various kinds of approaches have been developed to generate WLED, in which phosphor-convered light emitting diode (pc-LED) develop rapidly because of the mature preparation process, simple circuit design and control, and low cost. At present, the most usual WLED is the combination of blue LED with yellow YAG:Ce phosphor, but the WLED with this pattern has poor coloration index and high color temperature for the deficiency of red color. In addition, although the trichromatic WLED based on ultraviolet (UV) InGaN chip has good coloration index, it also requires red phosphors with high efficiency. Therefore, searching for the red phosphor, which can be effectively excited by blue LED and UV-LED, is an important research topic for WLED lighting.In this paper, a series of Ca2La8Si6O26:Eu red emitting phosphors were synthesized by the conventional solid-state reaction route. The effects of calcining temperature, reaction time, precalcining condition, flux content and Eu3+ concentration were studied on the crystal structure, morphology and luminescent properties of the red phosphors. On the basic of single factor experiments, the optimum synthesis conditions of the red phosphor had been obtained with orthogonal design, then the obtained sample was modified by changing the matrix cationic and doping sensitizer. Furthermore, series of Ca2La8Si6O26:Eu red emitting phosphors were synthesized by the sol-gel route in the study. The influences of calcining temperature and Eu3+ concentration on the luminescent properties of the red phosphors were investigated. Lastly, there was a comparative analysis on the crystal structure, morphology, luminescent properties and photochromic properties of the samples prepared respectively by the solid-state route and the sol-gel route.The results indicated that:the optimum calcining temperature, reaction time, precalcining condition, flux content, and Eu3+concentration of the Ca2La8Si6O26:Eu red phosphor are 1450℃,4h,1000℃/2h,4.5% and 0.3, respectively. The emission and excitation spectra of Ca2(La0.7Eu0.3)8Si6O26 phosphor exhibit that the phosphor can be effectively excited by near UV light (394nm) and blue light (464 nm), and emits a satisfactory red light at 614nm. The excitation spectrum matches well with the output wavelengths of UV or blue LED chips, which indicates that Ca2(La0.7Eu0.3)8Si6O26 may be applicable in the fabrication of WLED.The emission intensity, relative brightness and R/O values of the series samples of M2(La0.7Eu0.3)8Si6O26(M=Ca, Sr, Ba) gradually decrease according with increasing ion radius of M2+, indicating that the same charge cationic with the smaller radius is beneficial to the electric dipole transition (5D0→7F2 transition)of Eu3+. Bi3+ ion has a sensitization effect to the luminescence of Eu3+ ion, and the optimum Bi3+ concentration is 0.05mol, at this point, the relative brightness value of sample reaches the maximum, and emission intensity increases by 17.0%. Furthermore, there is also a stronger asymmetry in Ca2La8Si6O26 lattice with the incorporation of Bi3+, which is in favor of the luminescence of Eu3+ ion in the red region.Calcined at 750℃, the sample with single Ca2La8Si6O26 phase can be obtained by the sol-gel method. Rising the temperature to 850℃, the calcined sample obtains the best luminescence properties. Compared with the solid-state reaction route, synthesis temperature of sample prepared by the sol-gel route is much lower, while excitation intensity, emission intensity and relative brightness are lower. As the raw materials can be mixed uniformly on the molecular or even atomic level in sol-gel process, quenching concentration of Eu3+ can reach up to 0.5, higher than that of the solid-state reaction. Based on emission spectra, it can be calculated that the chromaticity coordinates of the optimized phosphors prepared respectively by the solid-state route and the sol-gel route are (0.647,0.353)and (0.651,0.349), suggesting that both samples possess high color purity and show reddish orange color. And the phosphor, prepared by the sol-gel route, can be more effectively excited by near UV light (394 nm), and beneficial to improve red color emission.
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