Investigation of structural and optical properties of Ba۰.۶Mg۰.۲Ca۰.۲Al۲O۴ceramic

Barium aluminate (BaAl۲O۴) is an insulator with hexagonal crystal structure, and itcrystallized in space group P۶۳ (No. ۱۷۳) symmetries with cell parameters a = b= ۱۰.۴۴۹,c = ۸.۷۹۳ Å. It belongs to the family of stuffed tridymite tetrahedral structures. This structureconsists of twisted AlO۴ tetrahedral linked to each other by their corners [۱]. Metal ion-dopedBaAl۲O۴ ceramics possess wide applications in the fabrication of efficient phosphor materials. Inresearches [۲ and ۳], a broad emission band at about ۴۰۵ nm in the spectrum of undoped, nonreducedBaAl۲O۴ were reprted. Pandey and Chithambo [۲] measured PL with UV-excitation at۲۴۸ nm and thermoluminescence, while the Benourdja et al. [۳] evaluated CL spectra. Bothauthor groups ascribed the broad emission band to native defect state transitions in BaAl۲O۴.Suriyamurthi and Panigrahi [۴] reported the PL at room temperature of undoped BaAl۲O۴ byexcitation with near UV light at ۳۴۶ nm. They measured a main emission band at ۵۰۰ nm and ashoulder at ۴۳۰ nm and relatively assign these emission bands to Vk۳+ defect centres. Thesecontradictory results indicate that apart from the processes mentioned above, viz. annealing andexcitation, there could be non-registered parameters such as synthesis conditions, purity, storagecondition, etc. that affect the nature and concentration of defects in BaAl۲O۴. In this research,Ba۰.۶Mg۰.۲Ca۰.۲Al۲O۴ ceramic was fabricated by sol-gel route and its optical and structuralproperties was evaluated compared to BaAl۲O۴ by techniques such as X-ray diffraction (XRD),field-emission scanning electron microscopy (FE-SEM), energy-disspersive X-rayspectroscopy (EDS), ultraviolet-visible (UV–Vis), and photoluminescence (PL).

Keywords:

ceramic , optical properties , structural properties , sol-gel approuch