Photoluminescence behavior of MO3-B2O3-CeO2-Bi2O3 (M = Mo or W) glasses and their counterparts nano-glass-ceramics

8MO(3)-30B(2)O(3)-xCeO(2)-(62-x)Bi2O3 glasses (where M = Mo or W and x = 2,5,8; in mol%) were fabricated employing the conventional melt-quench method. Differential thermal analysis was utilized to determine the peaks of crystallization temperatures at which a successful nano-crystallization has been achieved. The obtained nano-glass-ceramics include nano-crystallites of monoclinic bismuth molybdate (Bi2MoO6) and orthorhombic Russellite (Bi2WO6) as major crystalline phases within the Mo- and W-containing glassy matrices, respectively. Morphology of these nano-crystallites was investigated by High resolution transmission electron microscope which revealed average crystallites sizes in the range of 6-26 nm. The influence of CeO2 on photoluminescence (PL) of the as-quenched glasses as well as their counterparts nano-glass-ceramics was studied and discussed. PL spectroscopy indicated that the glasses are pure red phosphors emitting red light at 600 and 610 nm upon UV excitation at 300 nm where no blue emission band was resolved, neither due to Bi3+ ions nor due to Ce3+ ions. This was attributed to the oxidizing power of CeO2 in the glass system producing more Bi2+ ions which emit the red light in conjugation with the deactivation effect of Ce3+ ions which suppress the blue emission of Bi3+ ions. The nano-glass-ceramics exhibited very broad emission spectra, extending in a wide range in the visible region, which consist of prominent blue emissions with a minority of green and red emission bands under UV excitation at 254 and 280 nm.