Effect of Li⁺ Ions Doping on Microstructure and Upconversion Emission of Y₂Ti₂O₇:Er³⁺/Yb³⁺ Nanophosphors Synthesized Via a Sol–Gel Method

Abstract

O 7 nanophosphors were synthesized via a facile sol-gel process. The samples were characterized by the inductively coupled plasma atomic emission spectrometer (ICP-AES), X-ray diffraction (XRD), transmission electron microscopy (TEM), and infrared-to-visible upconversion (UC) luminescence spectra. XRD analysis showed that the crystallization temperature of pyrochore-type Y 2 Ti 2 O 7 was reduced due to the flux effect of Li + ions, whereas TEM measurements confirmed that the particles size of (Y 0.815 Er 0.01 Yb 0.075 Li 0.10 ) 2 Ti 2 O 7 was about 30-40 nm when calcining at 800°C for 1.0 h. The calcining temperature and Li + ion concentration dependence on UC luminescence spectra were investigated. It was found that, when incorporating 10.0 mol% Li + ion, the UC red and green emission intensity was drastically increased by a factor of 18.6 and 8.3, respectively. The enhancement of UC emission may be mainly attributed to the modification of local symmetry around Er 3+ ions by tridoping Li + ions. And also, the pump power dependence of the emission intensity was investigated to understand the fundamental UC mechanism.A. Srivastava-contributing editor Manuscript No. 31924.

Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method

“…Here, the shape of the emission spectra (Figure 4b) confirms that the Eu 3+ ions occupy sites with D 2d point symmetry (sites without an inversion center), i.e., they replace the Gd 3+ ions. This finding further confirms and complements those from the XRD results3132. Apart from the smaller emission intensities in the NPs compared to the bulk material, no other differences between the emission spectra could be observed (no changes in the band shapes and no band shifts).…”

Concentration and pump power-mediated color tunability, optical heating and temperature sensing via TCLs of red emission in an Er3+/Yb3+/Li+ co-doped ZnGa2O4 phosphor

“…It also creates oxygen vacancies to maintain charge neutrality in the phosphor. 44 These parameters contributed signicantly to the improvement of UC emission intensity of the phosphor. The UC emission intensity of the Er 3+ /Yb 3+ co-doped Y 2 O 3 nanocrystals is also found to increase due to similar reasons by Li + doping.…”

“…Out of these ions, the Li + ion has been widely incorporated in different combinations of Er 3+ /Yb 3+ codoped phosphor materials. [42][43][44][45] It has been noted that the Li + ion can easily enter into the sites of host lattices due to its smaller ionic radius and has been proved as a suitable surface modier. Zhao et al have reported Li + ions as a doping element for improving the crystallinity and UC emission intensity in NaYF 4 :Tm 3+ /Yb 3+ nanoparticles.…”

Enhancement of up-conversion luminescence of Y₂Ti₂O₇:Yb³⁺/Ho³⁺ nanocrystals by incorporating Li⁺ ions

“…Actually, the reduction of crystallization temperature of the samples can be ascribed to the flux effect of the introduction of hetero-atoms such as Li + and Zn 2+ ions, and this similar phenomenon was also observed by Liu et al 21), 22) and our previous experiments. 14) In the current system, no obvious change exists in the crystallinity of products when the doping concentration of Li + ions is greater than 5.0 mol %. For better understanding of the influence of the doping level of Li + ions on the XRD positions, the most intensive XRD peaks (222) are displayed, as shown in Fig.…”