Abstract
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.
Highlights
We report a method for polyethylene glycol (PEG)-assisted hydrothermal synthesis of Yb3+ doped lithium lutetium fluoride (Yb:LLF) microcrystals and discuss the influence of various factors on the growth of the Yb:LLF microcrystals and their ability to undergo laser refrigeration
X-ray diffraction analysis confirms that crystals from both syntheses adopt a tetragScanning electron microscopy (SEM) of two different Yb:LLF crystals are shown in onal scheelite structure (ICDD number 04-002-3255) with space group I41 /a (Figure 2c)
We show that size and morphology can be finely controlled by changing reaction conditions such as temperature, time, fluoride source, and precursor amount
Summary
Rare earth lithium fluorides (RELiF4 ) with a scheelite structure are widely used in various fields such as theranostics [1], long-term in vivo bioimaging [2,3], photothermal therapy [4,5,6], ratiometric temperature sensing [7], transparent volumetric displays [8,9], multi-level anti-counterfeiting applications [10], photocatalysis [11], photovoltaics [12], scintillating materials [13], and refrigeration through laser radiation [14,15,16,17,18,19,20]. The substitution of Li+ in Na(1–x) Lix ReF4 causes a phase transition and induces variation in the morphology, size, and luminescent properties of the final microcrystals [28]
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