Strong luminescence enhancement of Li^sub 2^CaSiO^sub 4^:Eu^sup 2+^ phosphors by codoping with La^sup 3

Issue Title: Special Issue: Failure Analysis in Electronic Devices and Materials La^sup 3+^ ions codoped Li^sub 2^CaSiO^sub 4^:Eu^sup 2+^ phosphors were synthesized through the solid state reaction method. Large increases in the emission could be achieved by adding La^sup 3+^ in the host. The optimum doping concentration expressed by the x value in Li^sub 2^Ca^sub 0.99-x^SiO^sub 4^:0.01Eu^sup 2+^, xLa^sup 3+^ was determined to be of 0.01. X-ray diffraction patterns revealed that the samples maintained Li^sub 2^CaSiO^sub 4^ single phase after codoping Eu^sup 2+^ and La^sup 3+^. 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 Eu^sup 2+^ peaks at about 478 nm (4f^sup 6^5d^sup 1^-4f^sup 7^). 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 La^sup 3+^ codoped could increase the excited state energy and prolong the lifetime of Eu^sup 2+^. The optimization mechanism was studied in detail by the case of La^sup 3+^ codoping. The temperature dependent luminescence measurements show that the thermal quenching remains small in the case of La^sup 3+^ doping, in other word, La^sup 3+^ codoped Li^sub 2^CaSiO^sub 4^:Eu^sup 2+^ phosphor has a good thermal stability. These results provided a useful basis for further improving the luminescence performance of Li^sub 2^CaSiO^sub 4^:Eu^sup 2+^ phosphors.[PUBLICATION ABSTRACT]