Reflection dynamics of tulium oxide in complex with ytterbium and bismuth oxides in the visible wavelength range

The paper presents the study of optical reflection spectra of rare-earth element oxide complexes (Tm₂O₃/Bi₂O₃, Tm₂O₃/Yb₂O₃, Tm₂O₃, Bi₂O₃, Yb₂O₃) . It is shown that the presence of ytterbium oxide in the Tm₂O₃/Yb₂O₃ mixture leads to a decrease in the reflection coefficient of tulium oxide in the ultraviolet region of the spectral range. In the presence of bismuth oxide in the Tm₂O₃/ Bi₂O₃ mixture the reflection maximum in the 350 nm range decreases 1.5 times. In the visible region of radiation in complexes with Tm₂O₃ at wavelengths of 462 and 475 and 490 nm there are minima of reflection coefficient equal to 85-90%. These minima correspond to transitions from the vibrational levels of the ground state ³H₆ → ¹G₄. This indicates that the Tm₂O₃/ Bi₂O₃ complex in the presence of Tm₂O₃ allows the reflection coefficients to increase in the visible region. The processes of electron excitation energy transfer have been investigated, as a result of which the effects of photoluminescence can be observed. The study also included the possible ways of energy transfer between the interacting centers, taking into account the upconversion luminescence of ytterbium oxide in the red region of the spectrum. It has been found that ytterbium or bismuth acts as a donor of energy transfer in paired complexes. X-ray structural analysis of bismuth oxide has been investigated, from which it follows that the synthesized phase of bismuth oxide Bi₂O₃ corresponds to monoclinic symmetry. Further studies will be related to the establishment of mechanisms of photoluminescence formation in the presented complexes and determination of the dynamics of the duration of excited states existence on the basis of spectral-kinetic studies. The study of photoluminescence processes is a major practical task.

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