Structural and luminescent characteristics of two-step processed BaAl2−xSixO4−xNx:Eu2+ phosphors

Abstract

Green emitting BaAl2−xSixO4−xNx:Eu2+ phosphors were synthesized using high temperature solid state reaction via two step process for white LED applications. The effect of (SiN)+ incorporation on structural and luminescent properties of BaAl2O4:Eu was studied. XRD analysis shows that solid solution is obtained upto x=0.50 beyond which phase segregates. The lattice parameters are found to decrease and cell volume shrinks with (SiN)+ incorporation due to the reduction in bond length of Si–N compared to Al–O in host lattice. The peak wavelength of PL emission from the samples, when excited using 450nm light, was found to red shift with SiN incorporation upto x=0.50 beyond which no shift was observed. The PL emission intensity was found to be maximum for x=0.80 (SiN)+ incorporation in to the host lattice. The chemical shift of 27Al solid state MAS NMR spectra shows the presence of AlO4−xNx tetrahedra at higher SiN concentrations. From the XPS and FTIR analysis of the samples, the presence of SiO, SiN, SiON, AlO, AlN and AlON bondings were detected and even though phase segregates at x=0.50, nitrogen is incorporated in the host lattice which resulted in the enhanced absorption at 450nm.