Comparative study of optical and structural properties of micro- and nanocrystalline SrAl2O4: Eu2+, Dy3+ phosphors

Abstract

Micro- (MC) and nanocrystalline (NC) strontium aluminate (SrAl2O4: Eu2+, Dy3+) phosphor powders are synthesized separately by solid state reaction (SSRT) and combustion synthesis technique (CST) respectively. The characterization features of both types of samples (MC and NC) are compared using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) while the optical properties are discussed in terms of photoluminescene (PL), after glow (AG) and thermoluminescence (TL) measurements. The SEM results show agglomeration of particles in both the cases and signify the presence of comparatively smaller particles in NC phase. The results of XRD studies indicate the presence of monoclinic SrAl2O4 exhibiting wider diffraction peaks in NC samples as compared to their MC counterpart. The EDX profiles are used to confirm the presence of different starting materials. The absorption spectra and corresponding Tauc׳s plots confirm the wide band-gap of prepared samples. The emission spectra for MC samples are found to be more intense as compared to NC samples. For the MC samples the spectra exhibit a broad band emission accompanied by a peak at 520nm, which in the case of NC samples it shifts to 515nm. The broad emission band peaking is attributed to the typical 4f65d1–4f7 transitions of Eu2+. For MC samples the different TL peaks fall in a temperature range 139–171°C while for NC samples the curves peak in temperature range 95–111°C, indicating existence of only one trap center.