Hydrothermal Synthesis and Solid-State Laser Refrigeration of Ytterbium-Doped Potassium-Lutetium-Fluoride (KLF) Microcrystals

Xia, Xiaojing; Pant, Anupum; Zhou, Xuezhe; Dobretsova, Elena; Bard, Alexander B.; Lim, Matthew B.; Roh, Joo Yeon; Gamelin, Daniel R.; Pauzauskie, Peter J.

doi:10.1021/acs.chemmater.1c00420

Cited by 13 publications

(5 citation statements)

References 51 publications

(86 reference statements)

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“…After submerging the recovered NaYF gel in a concentrated (1 M) KF solution, we observed that the remaining sodium-poor regions incorporated KF to form KY 3 F 10 (KYF) (Figure 3A), which was distinguishable in XRD after the gel is allowed to fully condense into single crystals (Figure 3B). While KYF can form in multiple stoichiometries and structures, 45 the cubic KY 3 F 10 phase likely forms in this case because it is isostructural with the cubic NaYF structure, and requires less diffusion of KF into the solid than other KYF phases. We quantified this process by incubating the gel in its native solution for a set period of time (t inc ) before filtering and transferring it to the KF solution for long enough for it to fully crystallize (typically overnight).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Chemically Driven Multistep Crystallization in the Synthesis of Sodium Yttrium Fluoride Via a Porous, Electrochemically Active Intermediate

Bard,

Felsted,

Ganas

et al. 2024

J. Phys. Chem. C

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Two-step crystallization mechanisms based on liquid−liquid phase separations followed by crystallization are commonly observed both in the laboratory and in nature. While this pathway quite often occurs as a result of a chemical reaction, the subsequent nucleation and growth are often considered as separate, discrete events from the reaction itself. We show this mechanism in the aqueous synthesis sodium yttrium fluoride, but by using a combination of experimental techniques and computational modeling, we show an additional step of solid-state chemical diffusion that is essential to the nucleation mechanism. In this system, we observe at least four distinct steps in the crystallization process, including (1) the segregation of aqueous ions into a dense liquid phase, (2) the formation of a metastable amorphous aggregate, (3) the continuous, gradual solid-state diffusion of sodium and fluoride ions into the amorphous aggregate toward a NaYF 4 stoichiometry, and (4) the crystallization of a stable cubic sodium yttrium fluoride phase. Unlike previous descriptions of nucleation and growth, we find that the stoichiometry of the final solid phase evolves throughout the crystallization process rather than being determined at the time of the initial separation from solution. This emphasizes that the chemical reaction cannot be assumed to be a separate event from the phase separation and growth, especially in compounds with variable stoichiometry. We also find that the amorphous aggregate that forms prior to the ion incorporation step adopts a porous, gel-like structure, which we isolated and showed to be electrochemically active, allowing for its potential use as a battery anode in lithium and sodium ion batteries, among other potential applications.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Chemically Driven Multistep Crystallization in the Synthesis of Sodium Yttrium Fluoride Via a Porous, Electrochemically Active Intermediate

Bard,

Felsted,

Ganas

et al. 2024

J. Phys. Chem. C

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“…The orthogonal KLu 2 F 7 belongs to a space group of Pna2 1 with lower symmetry, 27 which facilitates the anisotropic growth of KLu 2 F 7 at the nanoscale, enabling the construction of nanoflakes with a high surface-to-volume ratio. 28 Herein, a novel strategy was demonstrated to construct quasi-2D KLu 2 F 7 :20%Yb 3+ /2%Er 3+ @KLu 2 F 7 core−shell nanoflakes with a large specific surface area to amplify the surface thermal enhancement behavior.…”

Section: ■ Introductionmentioning

confidence: 99%

Huge Thermal Enhancement of Surface-Dominant Quasi-2D Upconversion Nanoflakes

Sun

Shang

Chen

et al. 2023

ACS Sustainable Chem. Eng.

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Long-term thermal quenching of upconversion (UC) limits the usage of UC materials in nanothermometers, lighting phosphors, etc. Although UC thermal enhancement has been achieved through thermal alleviation of surface quenching, the regulation of the balance between internal multiphonon nonradiative relaxation-induced thermal quenching and external surface quencher release-induced thermal enhancement is still a big challenge. Here, we demonstrate a new strategy to achieve huge UC thermal enhancement by constructing surface-dominant quasi-2D KLu2F7:20%Yb3+/2%Er3+@KLu2F7 core–shell nanoflakes with an ultrathin thickness of 1.5 nm. The surface-dominant design enables enhancements of ∼820-fold at the 523 nm band and ∼304-fold in total as the temperature increases from 303 to 463 K. Similar huge UC thermal enhancements are also observed in Ho3+ (∼383-fold)- and Tm3+ (∼324-fold)-doped nanoflakes. Higher relative and absolute sensitivities of the thermally coupled state pairs (Er3+:2H11/2/4S3/2) with respective plateau values of 0.940% K–1 (303 K) and 0.509% K–1 (463 K) are achieved, which obviously outperform the thermal-quenching NaYF4:20%Yb3+/2%Er3+@NaYF4 nanoparticles. Moreover, the highly thermally enhanced nanoflakes enable the development of temperature-dependent anticounterfeiting inks and encryption, favoring the high-temperature usage of luminescence materials.

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“…Recently, it has been demonstrated that low-cost, low-temperature hydrothermal processing can be used to grow YLiF 4 [17], NaYF 4 [22], KLuF 4 [23], and LiLuF 4 [24] crystals that are capable of solid-state laser refrigeration. However, the use of ammonium bifluoride inhibits the production of large amounts of these materials due to the danger of hydrofluoric acid formation in solution, which can then form gaseous hydrogen fluoride during the autoclave portion of the synthesis.…”

Section: Introductionmentioning

confidence: 99%

Safe and Scalable Polyethylene Glycol-Assisted Hydrothermal Synthesis and Laser Cooling of 10%Yb3+:LiLuF4 Crystals

et al. 2022

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Rare earth doped lithium fluorides are a class of materials with a wide variety of optical applications, but the hazardous reagents used in their synthesis often restrict the amount of product that can be created at one time. In this work, 10%Yb3+:LiLuF4 (Yb:LLF) crystals have been synthesized through a safe and scalable polyethylene glycol (PEG)-assisted hydrothermal method. A combination of X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and photoluminescence (PL) measurements were used to characterize the obtained materials. The influence of reaction temperature, time, fluoride source, and precursor amount on the shape and size of the Yb:LLF crystals are also discussed. Calibrated PL spectra of Yb3+ ions show laser cooling to more than 15 K below room temperature in air and 5 K in deionized water under 1020 nm diode laser excitation measured at a laser power of 50 mW.

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Hydrothermal Synthesis and Solid-State Laser Refrigeration of Ytterbium-Doped Potassium-Lutetium-Fluoride (KLF) Microcrystals

Cited by 13 publications

References 51 publications

Chemically Driven Multistep Crystallization in the Synthesis of Sodium Yttrium Fluoride Via a Porous, Electrochemically Active Intermediate

Chemically Driven Multistep Crystallization in the Synthesis of Sodium Yttrium Fluoride Via a Porous, Electrochemically Active Intermediate

Huge Thermal Enhancement of Surface-Dominant Quasi-2D Upconversion Nanoflakes

Safe and Scalable Polyethylene Glycol-Assisted Hydrothermal Synthesis and Laser Cooling of 10%Yb3+:LiLuF4 Crystals

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