Abstract
Powder samples of undoped and Pr-doped Y 2 O 3 are synthesized by the reverse precipitation method and annealed at 1000 °C for 1 h. X-ray diffraction patterns confirm the presence of the well-known Y 2 O 3 cubic phase. The optical properties of the compounds are characterized by diffuse reflectance and photoluminescence spectroscopies. The presence of a huge absorption band in the Pr-doped samples is attributed to the presence of Pr 4+ , but also emission and excitation luminescent spectra reveal the existence of Pr 3+ . To explain the origin of the broad absorption band, it is made use of an approach formulated decades ago based on the assumption that ligand-to-metal charge transfer states O 2−/- → Pr 4+/3+ are involved. To implement this approach, a deconvolution of the absorption spectrum, following a judicious conjecture based on phenomenological methods in which each deconvolution's component is associated with a transition from the top of the valence band, mainly O-2p in character, to each of the Pr 3+ f-f states, or from the Pr 3+ - 3 H 4 ground state to one of its d states, is performed. Our results match consistently with those energies calculated from a vacuum referred binding energy diagram, allowing to rationalize the presence of a huge absorption band as well as to explain the absence of the emission coming from the most energetic Pr 3+ electronic transitions when Pr 4+ is present in Pr-doped Y 2 O 3 . • A huge absorption band in Pr-doped Y 2 O 3 is attributed to the presence of Pr 4+ . • This band is due to ligand-to-metal charge transfer states O 2−/- .→ Pr 4+/3+ . • The presence of such states is proven by deconvoluting the absorption spectrum. • A VRBE diagram Y 2 O 3 /Pr 3+ allows to guess the deconvolution's components. • The VRBE diagram also lets to rationalize the optical properties in Pr-doped Y 2 O 3 .
Published Version
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