Eu 3+ -doped Bi 4 Si 3 O 12 red phosphor for solid state lighting: microwave synthesis, characterization, photoluminescence properties and thermal quenching mechanisms.

Europium-doped bismuth silicate (Bi4 Si3 O12 ) phosphor has been prepared by microwave irradiation method and its crystal structure is determined using Rietveld method. As-prepared phosphor consists of spherical, monodispersed particles with few agglomeration, high crystallinity, and narrow grain size distribution. The phosphor can be efficiently excited in the wavelength range of 260-400 nm, which matched well with the emission wavelengths of NUV LED chips. The photoluminescence spectra exhibit the highest emission peak at 703 nm originating from 5 D0  → 7 F4 transition of Eu3+ under NUV excitation. The luminescence lifetime for Bi4 Si3 O12 : 2 at% Eu3+ phosphor decreases from 2.11 to 1.86 ms with increasing temperature from 10 to 498 K. This behavior of decays is discussed in terms of radiative and nonradiative decays dependence on temperature. The thermal quenching mechanism of 5 D0 emission of Eu3+ in Bi4 Si3 O12 phosphor is a crossover process from the 5 D0 level of Eu3+ to a ligand-to-europium (O2-  → Eu3+ ) charge transfer state. The quantum efficiency of the phosphor under 393 nm excitation is found to be 14.5%, which is higher than that of the commercial red phosphors Y2 O3 : Eu3+ , Y2 O2 S: Eu3+ . The temperature effect on CIE coordinate was discussed in order to further investigate the potential applications.