Niobium enhanced Europium ion luminescence in Hafnia nanocrystals

K. Laganovska*, I. Bite, A. Zolotarjovs, K. Smits

In this work we demonstrate a method where by adding Nb ions, Ln3+ ion lumi
nescence intensity in HfO2 is increased for up to 15 times (in a sample containing
5mol%Eu). The effect is described as niobium acting as a charge compensator and neutralizing the charge resulting from Ln3+ ion insertion in Hf4+ site and
hence reducing the number of defects present. This is the second system where
such an effect was observed, so it is expected that other metal oxides would show the same effect. The optical properties of HfO2:Eu3+ and HfO2:Eu3+, Nb5+,
synthesized using the sol-gel method and annealed at various temperatures are
studied. A conclusion that the structure of hafnia does not affect luminescence
intensity directly and a larger role is played by factors such as defect presence
and the size of the particles is drawn based on XRD and TSL measurements.
Time-resolved luminescence measurements were also carried out and significant
changes depending on dopant concentration and annealing temperatures were
observed. Judd Ofelt theory was used to determine quantum efficiency and the local symmetry of Eu3+ ion sites.
Keywords: Hafnia, Luminescence, Eu3+, Charge compensation, Judd Ofelt

Published in Journal of Luminescence

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