The role of Nb in intensity increase of Er ion upconversion luminescence in zirconia

Abstract

It is found that Nb co-doping increases the luminescence and upconversion luminescence intensity in rare earth doped zirconia. Er and Yb-doped nanocrystalline samples with or without Nb co-doping were prepared by sol-gel method and thermally annealed to check for the impact of phase transition on luminescence properties. Phase composition and grain sizes were examined by X-ray diffraction; the morphology was checked by scanning-and high-resolution transmission electron microscopes. Both steady-state and time-resolved luminescence were studied. Comparison of samples with different oxygen vacancy concentrations and different Nb concentrations confirmed the known assumption that oxygen vacancies are the main agents for tetragonal or cubic phase stabilization. The oxygen vacancies quench the upconversion luminescence; however, they also prevent agglomeration of rare-earth ions and/or displacement of rare-earth ions to grain surfaces. It is found that co-doping with Nb ions significantly (>20 times) increases upconversion luminescence intensity. Hence, ZrO 2 :Er:Yb:Nb nanocrystals may show promise for upconversion applications. V

Upconversion luminescence in erbium doped transparent oxyfluoride glass ceramics containing hexagonal NaYF4 nanocrystals

“…In case of the green luminescence, two possible routes, namely, excited state absorption (ESA) and energy transfer upconversion (ETU) can be distinguished. In the ESA process, sequential absorption of two infrared photons ( 4 I 15/2 → 4 I 11/2 → 4 F 7/2 ) promotes Er 3+ into 4 F 7/2 state [50]. Alternatively, in the ETU process mutual interaction between two Er 3+ ions previously excited to 4 I 11/2 leads to deexcitation of one of the ions to the ground state while the other one is promoted to 4 F 7/2 .…”

Niobium enhanced europium ion luminescence in hafnia nanocrystals

“…As it is expected for the structure and the resulting luminescence intensity of hafnia to be dependent on the size of nanocrystal grains, all samples were annealed at three different temperatures: 800°C, 1000°C, 1200°C, similar to the approach used in other research works [11,10,14].…”

“…This effect was proven by experimental studies performed on ZrO 2 matrix [10]. Recent studies [7,11,12] showed that in zirconia a strong overall reduction in + Ln 3 luminescence intensity can be explained by intrinsic defects. However, the implementation of + Nb 5 ions as charge compensators in the matrix can change the defect concentration and distribution thus highly increasing the resulting intensity.…”

An Upconversion Niobium Pentoxide Bulk Glass Codoped with Er3+/Yb3+ Fabricated by Aerodynamic Levitation Method

“…From Raman spectra, the difference of the maximum phonon energy between the NLZ15 and NL glasses is quite slight. The phonon density may affect the upconversion luminescence intensity …”