Low-Temperature Luminescence of Lu₂O₃:Eu Ceramics upon Excitation with Synchrotron Radiation in the Vicinity of Band Gap Energy

Abstract

Synchrotron radiation has been used to characterize the low-temperature (10 K) spectroscopic properties of Lu 2 O 3 :Eu phosphors containing varying amount of the dopant. Upon excitation at energies in the vicinity of the band gap, the nominally undoped specimen produced three different emissions. The highest energy luminescence, located at 260 nm, was attributed to direct recombination of electrons and holes. We also found a broad band emission at 380 nm, which we attribute to self-trapped excitons (STEs) on the basis of the excitation spectra of the various emissions. Finally, in doped specimens, we also recorded emission produced by the Eu 3+ activator. We found that the e-h recombination luminescence at 260 nm was severely quenched in the presence of Eu, disappearing completely at a concentration of 0.1 atom %. The 380 nm STE luminescence intensity decreased much more slowly with increasing Eu content, until at 5 atom % it too disappeared, leaving only the Eu 3+ emission. This emission became gradually more and more intense with increasing activator content. We found that while excitons carry more than enough excitation energy, they prefer to annihilate radiatively without passing their energy to Eu 3+ ions. Hence, we concluded that the only efficient channel of energy transfer from the excited host to the activator is through sequential trapping and subsequent recombination of free electrons and holes.

Spectroscopy and structural characteristic of Yb3+ and Nd3+ ions doped nanostructured Lu2O3 and sol–gel derived silica host materials

“…In the 950-1050 nm spectral region we can see a set of transitions related to the 2 F 5/2 → 2 F 7/2 emission of Yb 3+ . In the excitation spectra we can observed two bands, a broader and stronger one centered at 225 nm, assigned to the 2 F 7/2 → CT transition and less intense, sharp band at 212 nm that can be related to the formation of a free exciton [18,19]. All the emission lines can be excited both at 212 and 225 nm.…”

“…For the latter system the Scheme 1. The higher energetic band has an inflection on its lower energetic edge centered at 377 nm that can be recognized as the host lattice emission [18,19]. The energy separation between the two emission bands is 8570 cm −1 , less then energy difference between 2 F 7/2 and 2 F 5/2 states of Yb 3+ .…”

Synthesis of Lu₂O₃:Eu³⁺ Luminescent Ceramic Powder Embedded in SiO₂ Matrix

“…Lu 2 O 3 -ceramic powders with a molar ratio Lu : Si = 8 : 1 represent systems with efficient energy transfer from the ceramic matrix to the Eu 3+ ions resulting from a recombination of excited electrons to the conduction band and holes left in the valence band. 30) Taking these factors into consideration, it can be observed a good consistency between 20) indicating that both systems are quite comparable; also it is observed that increasing the SiO 2 content at a Lu : Si = 8 : 1 molar ratio, the intensity of the luminescence is enhanced effect that can be observed both powders and films.…”

New synthesis procedure for nanoparticulate Lu2O3:Eu and spectroscopy of the product

“…Just below 220 nm we observe a band, whose position and shape change with temperature. In the past it was showed that fundamental absorption of the lutetia host lattice is located just in this range of wavelengths [13]. At least up to 100 K the band contains the very characteristic sharp narrow structure of free exciton (FE) absorption peaking around 213.3-213.5 nm.…”