Strong luminescence enhancement of Li2CaSiO4:Eu2+ phosphors by codoping with La3+
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La3+ ions codoped Li2CaSiO4:Eu2+ phosphors were synthesized through the solid state reaction method. Large increases in the emission could be achieved by adding La3+ in the host. The optimum doping concentration expressed by the x value in Li2Ca0.99−xSiO4:0.01Eu2+, xLa3+ was determined to be of 0.01. X-ray diffraction patterns revealed that the samples maintained Li2CaSiO4 single phase after codoping Eu2+ and La3+. The excitation spectra of samples showed a broad absorption band ranging from 220 to 450 nm and the emission spectra excited at 375 nm showed the typical broad band of Eu2+ peaks at about 478 nm (4f65d1–4f7). The broad absorption band wavelength was found to be matched appropriately with the emission wavelength of commercially available blue LEDs. Fluorescent lifetime test results showed that the La3+ codoped could increase the excited state energy and prolong the lifetime of Eu2+. The optimization mechanism was studied in detail by the case of La3+ codoping. The temperature dependent luminescence measurements show that the thermal quenching remains small in the case of La3+ doping, in other word, La3+ codoped Li2CaSiO4:Eu2+ phosphor has a good thermal stability. These results provided a useful basis for further improving the luminescence performance of Li2CaSiO4:Eu2+ phosphors.
KeywordsExcitation Spectrum Diffuse Reflection Spectrum Solid State Reaction Method Eu2O3 Thermal Quenching
Financial supported from the Cooperation Project in Industry, Education and Research of Guangdong Province and Ministry of Education of China (No. 2010B090400021).
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