Broadband near ultra violet sensitization of 1 μm luminescence in Yb3+-doped CeO2 crystal

Abstract

Broadband spectral modification of near ultra violet (UV) light to infra-red (IR) light is investigated in Yb3þ-doped CeO2 polycrystalline ceramics sintered in different atmospheres (air, oxygen, and 95%N2-5%H2). The intense Yb3þ photoluminescence (PL) peaked at 970 nm was observed by the UV excitation at around 390 nm in the samples except those sintered under N2-H2. A broad photoluminescence excitation (PLE) band of Yb3þ luminescence peaked at 390 nm corresponds to the absorption band and the photocurrent excitation band in the non-doped CeO2 crystal, which are also in accordance with the PLE band of Eu3þ luminescence in the Eu3þ-doped CeO2. Judging from these results, the PLE band is attributed to the charge transfer (CT) band from O2 to Ce4þ, but not to the CT from O2 to Yb3þ. From the sintering atmosphere dependence of the PL and PLE, we found that the oxygen vacancies and Ce3þ impurities are not responsible for the 390 nm-absorption band but they work as a quenching center for the Yb3þ luminescence.