Structural, optical and magnetic properties of Y_3−0.02−xEr_0.02Yb _x Al₅O₁₂ (0 < x < 0.20) nanocrystals: effect of Yb content

Abstract

The paramagnetic Y3−0.02−x Er0.02Yb x Al5O12 (x = 0.02, 0.06, 0.10, 0.12, 0.18, 0.20) nanocrystals (NCs) were synthesized by the microwave-induced solution combustion method. The XRD, TEM and SEM techniques were applied to determine the NCs’ structures and sizes. The XRD patterns confirmed that the NCs have for the most part a regular structure of the Y3Al5O12 (YAG) phase. The changes of the distance between donor Yb3+ (sensitizer) and acceptor Er3+ (activator) were realized by changing the donor’s concentration with a constant amount of acceptor. Under 980 nm excitation, at room temperature, the NCs exhibited strong red emission near 660 and 675 nm, and green upconversion emission at 550 nm, corresponding to the intra 4f transitions of Er3+ (4F9/2, 2H11/2, 4S3/2) → Er3+ (4I15/2). The strongest emission was observed in a sample containing 18% Yb3+ ions. The red and green emission intensities are respectively about 5 and 12 times higher as compared to NCs doped with 2% of Yb3+. In order to prove that the main factor responsible for the increase of the upconversion luminescence efficiency is reduction of the distance between Yb3+ and Er3+, we examined, for the first time the influence of hydrostatic pressure on luminescence and luminescence decay time of the radiative transitions inside donor ion. The decrease of both luminescence intensity and luminescence decay times, with increasing hydrostatic pressure was observed. After applying hydrostatic pressure to samples with e.g. 2% and 6% Yb3+, the distance between the donor and acceptor decreases. However, for higher concentrations of the donor, this distance is smaller, and this leads to the effective energy transfer to Er3+ ions. With increasing pressure, the maximum intensity of near infrared emission is observed at 1029, 1038 and 1047 nm, what corresponds to 2F5/2 → 2F7/2 transition of Yb3+.

Microwave-Assisted Preparation of Luminescent Inorganic Materials: A Fast Route to Light Conversion and Storage Phosphors

“…Combustion relies on rapid oxidation that generates heat or as a sequence of exothermic chemical reactions between a fuel and an oxidant that is accompanied by the production of heat and the conversion of chemical species [85][86][87][88]. In the volume reaction model, also referred to as thermal explosion, the entire sample is uniformly heated to the ignition temperature, and the combustion reaction coincides in all parts of the sample.…”

“…The microwave-assisted combustion makes the synthesis even faster, in the order of tenths of seconds (Figure 8). [85,90] with permission from The Royal Society of Chemistry.…”

“…Such extensive modification in DMOs needs thorough consideration of the involved hazards, mainly microwave leakage. Reproduced from ref [85,90]. with permission from The Royal Society of Chemistry.…”

Up-Converting Lanthanide-Doped YAG Nanospheres

“…3 Al 5 O 12 (with Ln 3+ = Ho 3+ , Tb 3+ or Tm 3+ ) for the host matrix and the lanthanidedoped garnets, respectively. The selection of the composition (Y 3−x−y Ln x Yb y Al 5 O 12 with x = 0.03 and y = 0.3) is based on studies on YAG structures reported in the literature for which efficient upconversion responses were obtained (Liu et al, 2007;Mishra et al, 2014;Kamińska et al, 2020). The samples are respectively referenced as YAG, HoYAG, TbYAG, and TmYAG.…”

“…The interest in upconverting yttrium aluminum nanoparticles is increasing (Diaz-Torres et al, 2005;Li et al, 2005;Liu et al, 2007;Jain et al, 2018;Kamińska et al, 2020) because these materials can find applications in a wide variety of fields such as biomedicine, encoding, sensors, energy, security, and so on (Van der Ende et al, 2009;Chen and Xiaojun Zhao, 2012;Chen et al, 2014;Wang et al, 2015;Zhou et al, 2015;Kłonkowski et al, 2018). In this context, there is plenty of room for new materials based on lanthanide-doped YAG nanogarnets with upconversion properties.…”