Influence of barium defects in the host matrix on the structural and optical properties of CaAl2O4:Eu2+, Dy3+, Nd3+ nanoparticles

CaxBa1-xAl2O4: Eu2+, Dy3+, Nd3+ phosphor was synthesized using the combustion method at different concentrations of Ba(NO3)2. This was aimed at understanding the effects of Ba concentration on the material properties of the host matrix- calcium aluminate nanoparticles. The optical and structural properties of the synthesized compound were analyzed using X-ray diffraction (XRD), Fourier transform infra-red spectroscopy, scanning electron microscope (SEM) and ultra-violet visible (UV-Vis) spectroscopy. The XRD patterns exhibited a shift in the diffraction angles of the major peaks to a lower 2θ, with the exception of the 20 % Ba sample. Introduction of alkaline earth metals with different ionic radii into the host matrix of CaxBa1-xAl2O4: Eu2+, Dy3+ led to a change in the CaxBa1-xAl2O4: Eu2+, Dy3+, Nd3+ lattice and hence shift in the major peaks. The Debye-Scherrer formula was applied to estimate the sizes of the crystallites of the samples in their prepared state. It was noted that there was variation in the crystallite sizes with changes in concentrations of Ba(NO3)2. Moreover, the UV-Vis analysis revealed that the absorption intensity increased with an increase in barium concentration, and the absorption edge changed with variation in barium concentration. The band separation was also found to decrease with an increase in barium concentration such that at very high barium concentration the band gap was very small. The SEM micrographs showed that all the powders were agglomerated and shaped erratically with pores and cracks. These findings give an indication that indeed Ba creates defects within the host matrix hence can be used to engineer the material properties of the as-prepared CaxBa1-xAl2O4: Eu2+, Dy3+, Nd3+ phosphor nanoparticles.