Symmetry-Related Transitions in the Photoluminescence and Cathodoluminescence Spectra of Nanosized Cubic Y₂O₃:Tb³⁺

Abstract

Herein the photoluminescence spectra of nanosized cubic Y 2 O 3 :Tb 3+ having Tb 3+ concentrations varying between 0.1 and 10 Mol% are described. Low temperature cathodoluminescence spectra from these materials recorded in a scanning transmission electron microscope are presented and discussed. By studying the photoluminescence-spectra recorded at room temperature and focused on the 5 D 4 → 7 F 5 (C 2 ) and 5 D 4 → 7 F 5 (C 3i ) transitions, at 542.8 and 544.4 nm respectively, it was found that the critical distance for energy transfer from Tb 3+ ions at C 3i lattice sites to Tb 3+ ions at C 2 lattice sites was 1.7 nm; at distances >1.7 nm, which prevail at low Tb 3+ concentration, this energy transfer virtually stops. The gradual change of the excitation spectra upon increasing the Tb 3+ concentration is also explained in terms of energy transfer from Tb 3+ at C 3i sites to Tb 3+ at C 2 sites. Cathodoluminescence spectra recorded at low temperatures with the scanning transmission electron microscope provided additional evidence for this radiationless energy transfer. Recently we published a study on the cathodoluminescence (CL) of nanosized cubic Y 2 O 3 :Tb 3+ particles; 1 reference to this work will be made as Part 1. We identified a few peaks in the CL spectra that are related to Tb 3+ at C 3i sites in cubic Y 2 O 3 (the structure is that of the mineral bixbyite). In Part 1, we have indicated the C 3i sites by S 6 . The vast majority of the spectral lines in the CL spectra of Y 2 O 3 :Tb 3+ arise from C 2 type transitions. We also found evidence that the two strongest emission lines in the 5 D 4 → 7 F 5 transition cluster at 542.8 nm and 544.4 nm are split when recorded at low temperature. These spectral data provided insight into the energy flow from Tb 3+ ions at C 3i lattice sites to Tb 3+ ions at C 2 lattice sites: the critical distance between a Tb 3+ (C 3i ) donor ion and Tb 3+ (C 2 ) acceptor ion was found to be 1.7 nm, which is about 5 times larger than the shortest distance between a cation at a C 3i site and a cation at a C 2 site.1,2 It is the objective of the work described herein to gain more insight into the studies reported in Part 1 by measuring the photoluminescence (PL) spectra at room temperature and the CL spectra in a scanning transmission electron microscope (STEM) at low temperatures.Many authors have reported on the PL spectrum of Y 2 O 3 :Tb 3+ ; here we shall mention only the most relevant publications on the spectroscopic characteristics of Y 2 O 3 :Tb 3+ . An important result in Part 1 was the doublet structure of the 542 nm and 544 nm lines, which became noticeable at a temperature of 103 K. A similar result was reported by Song and Wang, 3 who also found 4 lines between 541 and 545 nm at 83 K. At 274 K these lines coalesced into two peaks, in which the 542 nm peak still showed a shoulder. Najafov et al. 4 showed the doublet structure of the 542 nm and 544 nm lines in the PL spectra of Y 2 O 3 :Tb 3+ with various Tb 3+ concentrations at room temperature. In the spectrum presented...

Red Shift of CT-Band in Cubic Y2O3:Eu3+upon Increasing the Eu3+Concentration

“…The main advantage of this procedure was that the E CT could be determined in a consistent way, instead of deriving it from a curve fitting procedure around the maximum that did not account for the small peak at 289 nm. In our previous work the deconvolution method with Gaussian profiles has been reported; [21][22][23] therefore, we may suffice by showing the results. In Fig.…”

“…The synthesis of Y 2 O 3 :Eu 3+ nanoparticles by the homogeneous hydrothermal decomposition of urea method which has been extensively described in our earlier work. [21][22][23][24][25] The ageing of the turbid suspensions after the onset of precipitation was continued for one hour at a temperature above 85…”

Cathodoluminescence of Y2O3:Ln3+ (Ln = Tb, Er and Tm) and Y2O3:Bi3+ nanocrystalline particles at 200 keV

“…The 551 nm peak originates from cation sites with C 2 symmetry, whereas the transition at 543 nm is a doublet consisting of peaks originating from cation sites with C 2 and cation sites with C 3i symmetry. 22,23 Since the temperature behaviours of the C 2 and C 3i transitions are different due to energy transfer from the C 3i states to the C 2 states, SR551 is a better choice for the present analysis. As mentioned above, radiance (integrated intensity) is the preferred quantity to describe temperature behaviour.…”

“…Until now, this type of energy transfer has been observed only in Y 2 O 3 and Lu 2 O 3 doped with the lanthanide ions such as Eu 3+ and Tb 3+ . 13,22,23,32 In 2006 Kravchenko et al 33 measured the magnetic properties of bismuth(III) oxy compounds and concluded that Bi 2 O 3 is paramagnetic, which indicates that Bi 3+ must have an unpaired electron in oxy compounds. This brings Bi 3+ closer to the lanthanide family and makes its energy transfer from the centrosymmetric site to the non-symmetric site more obvious, but still far from clear.…”

Nanosized (Y1−xGdx)2O2S:Tb3+ particles: synthesis, photoluminescence, cathodoluminescence studies and a model for energy transfer in establishing the roles of Tb3+ and Gd3+

“…For these deconvolutions a least squares t was carried out using Microso's solver tool, as described in our earlier work. 18,19 It can be seen that the CT-band of (Y 1Àx Gd x ) 2 -O 2 S:Tb 3+ , consisting of the proles p1, p2, p4 and p5, exhibits a red shi upon increasing the Gd 3+ content (increasing x).…”