Enhancement of the upconversion photoluminescence intensity in Li+ and Er3+ codoped Y2O3 nanocrystals

Enhancement of upconversion emission in Y3Al5O12:Er3+ induced by Li+ doping at interstitial sites

“…Consequently, when the concentration of Li + ions is below 7 mol%, Li + ions occupy substitutional sites, but with higher concentrations, Li + ions begin to take interstitial sites. Because both types of Li + occupancies would break the local crystal field symmetry around the Er 3+ ions, Li + doping could help to break the forbidden transitions, change the lifetime of energy levels and consequently enhance the UC intensity [7,12]. Fig.…”

“…Hence, the modification of rare-earth ions' local environment can be a promising route to enhance their luminescence intensity. It has recently been reported that substitutional site Li + could result in the enhancement of UC emission in Y 2 O 3 :Er 3+ and Gd 2 O 3 :Eu 3+ [7,8]. It indicates that the improved UC intensity may originate from the break of local crystal field symmetry around rare-earth ion by the Li + doping.…”

“…But, the forbiddance can be partially broken when the rare-earth ion situates at low symmetry sites [7][8][9][10]. Hence, the modification of rare-earth ions' local environment can be a promising route to enhance their luminescence intensity.…”

Blue upconversion luminescence of CaMoO4:Li+/Yb3+/Tm3+ phosphors prepared by complex citrate method

“…The enhancement of upconversion luminescence can result from the break and distortion of local crystal field symmetry around lanthanide ions such as Er 3+ ion by Li + [14,15]. Due to small size, Li + ion can easily enter into the host lattice, occupying not only the substitutional sites but also the interstitial sites [16,17], which can enhance upconversion luminescence by the break or distortions of crystal field around lanthanide ions.…”

Upconverting Nanoparticles

“…Guo et al have synthesised NaYF 4 -based nanocrystals by arrested precipitation at low temperatures and could only observe luminescence after annealing of the particles at 400-600 C [24]. The groups of Song and Zhang et al have used a combination of a sol-gel method and arrested precipitation to prepare nanocrystalline Y 2 O 3 -based upconverters [15,16]. They first prepared a gel from yttrium and lanthanide nitrates and ammonia hydroxide that was "arrested" by citrate ligands.…”