, Volume 20, Issue 4, pp 953-959
Date: 30 Mar 2010

Intense White Luminescence from Combustion Synthesized Ca12 Al14 O33 : Yb3+ /Yb2+ Single Phase Phosphor

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The Ca12Al14O33: Yb3+/Yb2+ single phase nano-phosphor has been synthesized through combustion route and its luminescence and lifetime studies have been carried out up to 20 K using 976 and 266 nm excitations. The samples heated in open atmosphere have shown the presence of Yb in Yb3+ and Yb2+ states. The 976 nm excitation results a cooperative upconversion emission at 486 nm due to the Yb3+ state and a broad band in the blue region and has been assigned to arise from the defect centers. The 266 nm excitation on the other hand results a broad emission band even from as-synthesized phosphor without doping of Yb, the width of which increases in presence of Yb due to the emission from Yb2+ ions formed in heated samples. The white emission covers almost whole visible region with bandwidth 190 nm. The ions in Yb2+ state has been found to increase with the increase in heating temperature up to 1,273 K. A back conversion of Yb2+ to Yb3+ has been observed for higher temperatures. Effect of boric and phosphoric acids as flux on the emission properties of Yb3+ and Yb2+ states have been examined and discussed. Quantum yield of emission has also been determined for different samples.