Drastic Ce3+ Insertion Enhancement in YAG Garnet Nanocrystals Through a Solvothermal Route

Cantarano, Alexandra; Testemale, Denis; Homeyer, Estelle; Okuno, Hanako; Potdevin, A.; Dujardin, Christophe; Ibanez, Alain; Dantelle, Géraldine

doi:10.3389/fmats.2021.768087

Cited by 9 publications

(5 citation statements)

References 51 publications

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“…This is because cerium cations in the YAG crystal lattice are inherently unstable due to their large ionic radius and highest 4+ valence. Consequently, under conditions of stoichiometry shift and high temperatures during vacuum sintering, the formation of small amounts of CeO 2 and CeAlO 3 phases is possible, but these phases are not detectable by the XRD method 47 . This leads to the loss of luminescence contribution from part of the cerium cations.…”

Section: Discussionmentioning

confidence: 99%

Silver nanoparticles as a new sintering additive for the fabrication of YAG:Ce optical luminescent ceramics

Kravtsov,

Medyanik,

Tarala

et al. 2023

J Am Ceram Soc.

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In this study, silver nanoparticles (NPs) were considered for the first time as a sintering additive in the manufacture of YAG:Ce luminescent ceramics. The influence of the addition of silver NPs on the sintering kinetics of ceramics was investigated. It was found that the addition of Ag NPs in the concentration range of 0.027–0.44 wt% does not result in the formation of secondary phases in YAG:Ce ceramics. It was demonstrated that the light transmission of ceramics is dependent on the concentration of Ag NPs. The use of NPs additive has made it possible to increase the light transmission of ceramics compared with the reference sample without sintering additives. The combination of two sintering additives, TEOS and silver NPs, enables the achievement of enhanced optical transparency in ceramics compared to the individual application of sintering additives. At an optimal silver concentration of 0.11 wt%, in combination with 0.5 wt% TEOS, a ceramic light transmission value of 77% was attained. The study has identified a correlation between the luminescence intensity of YAG:Ce ceramics and the concentration of silver NPs. It was observed that the utilization of low concentrations of the Ag additive had negligible impact on the luminescence properties, whereas the introduction of high concentrations of Ag NPs led to a deterioration in the luminescence and optical transparency of the ceramic.

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Section: Discussionmentioning

confidence: 99%

Silver nanoparticles as a new sintering additive for the fabrication of YAG:Ce optical luminescent ceramics

Kravtsov,

Medyanik,

Tarala

et al. 2023

J Am Ceram Soc.

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“…Interestingly, the maximum of the Ce 3+ emission band in CL spectra is notably shifted in the red range with an increase in the crystallization rate and distance from the seed of eutectic ( Table 1 ). This effect can be connected with a deviation of the Ce content in the respective eutectic samples and changing the crystal field strength in the dodecahedral positions of the garnet host [ 30 ] due to the incorporation of relatively large Ce 3+ ions (ionic radius of 1.143 Ǻ in CN = 8) instead of Y 3+ cations (1.019 Ǻ; CN = 8). Finally, that resulted in the observed long-wavelength shift of the Ce 3+ emission spectra.…”

Section: Luminescent Propertiesmentioning

confidence: 99%

Ce3+ Doped Al2O3-YAG Eutectic as an Efficient Light Converter for White LEDs

et al. 2023

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Ce3+ doped Al2O3-YAG eutectics were successfully grown by the horizontal directional crystallization method. The crystallization rate of eutectic growth was changed in the 1–7.5 mm/h range at a growth temperature of 1835 ℃. The microstructure of eutectic samples was investigated using scanning electron microscopy and X-ray microtomography. The intrinsic morphology of eutectic represents the stripe-like channel structure with a random distribution of the garnet Y3Al5O12 (YAG) and Al2O3 (sapphire) phases. The content of these phases in the stripes changes in the 52.9–55.3% and 46.1–47.1% ratios, respectively, depending on the growth rate of the crystallization of the eutectic samples. The luminescent properties of the eutectic demonstrated the dominant Ce3+ luminescence in the garnet phase. The luminescence of the Ce3+ ions in Al2O3 has also been observed and the effective energy transfer processes between Ce3+ ions in the Al2O3 and YAG garnet phases were revealed under high-energy excitation and excitation in the UV Ce3+ absorption bands of sapphire. The phosphor conversion properties and the color characteristics (Al2O3-YAG):Ce eutectic with different thicknesses were investigated under excitation by a blue LED. We have also tested the prototypes of white LEDs, prepared using a blue 450 nm LED chip and (Al2O3-YAG):Ce eutectic photoconverters with 0.15 to 1 mm thicknesses. The results of the tests are promising and can be used for the creation of photoconverters for high-power white LEDs.

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“…[ 14 ] More concretely, in stoichiometric systems, non‐typical YAG compositions have been demonstrated to form under conditions where phase formation occurs at relatively low temperatures, for example using solvothermal methods to access extremely high Ce 3+ concentrations in YAG:Ce nanopowders. [ 15 ] Similarly, melt‐quenching techniques offer non‐equilibrium routes to a range of metastable aluminates and gallates with similar chemistries to YAG, by crystallization at temperatures below those typically required for solid‐state reactions. [ 16–19 ]…”

Section: Introductionmentioning

confidence: 99%

“…13 More concretely, in stoichiometric systems, non-typical YAG compositions have been demonstrated to form under conditions where phase formation occurs at relatively low temperatures, for example using solvothermal methods to access extremely high Ce 3+ concentrations in YAG:Ce nanopowders. 14 Similarly, melt-quenching techniques offer non-equilibrium routes to a range of metastable aluminates and gallates with similar chemistries to YAG, by crystallisation at temperatures below those typically required for solid-state reactions. [15][16][17][18] Glassy YAG materials can be synthesised by containerless melt-quenching approaches including aerodynamic levitation 19 and spray pyrolysis methods, 20,21 and these crystallise into the cubic garnet structure at approximately 900°C, far below the range 1600-1700°C typically required for ceramic synthesis of YAG.…”

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confidence: 99%

Highly Nonstoichiometric YAG Ceramics with Modified Luminescence Properties

Cao

Becerro

Castaing

et al. 2023

Adv Funct Materials

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Yttrium aluminium garnet Y3Al5O12 (YAG) is a widely used phosphor host. Its optical properties are tuned by chemical substitution at its YO8 or AlO6/AlO4 sublattices, with emission wavelengths defined by a finite number of rare-earth (YO8 sublattice) and transition-metal (AlO6/AlO4 sublattice) dopants which have been explored extensively. Non-stoichiometric compositions Y3+xAl5-xO12 (x ≠ 0) may offer a route to new emission wavelengths by distributing dopants over multiple crystallographic sites, but deviation from Y3Al5O12 stoichiometry is difficult to achieve and limited generally to ≤ 1% excess Y 3+ .Here we report a series of highly non-stoichiometric YAG ceramics Y3+xAl5-xO12 (0 ≤ x ≤ 0.4), with up to 20% of the AlO6 sublattice substituted by Y 3+ , synthesised by advanced melt-quenching techniques. This impacts the up-conversion luminescence of Yb 3+ /Er 3+ -doped systems, whose yellow-green emission differs from the red-orange emission of their stoichiometric counterparts. This contrasts with YAG:Ce 3+ where the dopant ions occupy the YO8 sublattice exclusively, with down-conversion luminescence that is hardly affected by host non-stoichiometry. Beyond YAG, analogous highly nonstoichiometric systems should be obtainable for a range of functional garnets, demonstrated here by the successful synthesis of Gd3.2Al4.8O12 and Gd3.2Ga4.8O12. This opens the way to property tuning by control of garnet host stoichiometry, and the prospect of improved performance or new applications for garnet-type materials.Yttrium aluminium garnet Y3Al5O12 (YAG) is a widely used phosphor host material with notable commercial and technological applications in white LED lighting 1 , scintillation detectors 2 and solid state lasers. 3 Its crystal structure, of general formula A3B5O12, contains three A cations (Y 3+ ) per formula unit exclusively in 8-fold dodecahedral coordination by oxide (YO8), with five B cations (Al 3+ ) distributed between two octahedral (AlO6) and three tetrahedral (AlO4) sites. This provides chemical versatility, as the Y 3+ site can accommodate rare earth (RE 3+ ) dopants with a range of ionic radii spanning most of the lanthanide series, whilst the Al 3+ sites may be substituted by other transitionand post-transition metals, producing a range of characteristic emission bands that underpin its applications. This versatility can lead to relatively complex systems such as Y3Al2Ga3O12, where Ce 3+ and Cr 3+ can be co-substituted with tuning of the Al 3+ /Ga 3+ ratio to generate high performance persistent phosphors. 4,5 Whilst A and B sites can host many different substituents, the structure is far less tolerant of deviations from A3B5O12 stoichiometry, to the extent that YAG is often considered as an archetypal line phase. Nevertheless, off-stoichiometric (as opposed to highly non-stoichiometric) Y-rich single crystals have been reported by melt-growth of aluminate and gallate garnets, [6][7][8] with the presence of ≤ 1 at.% excess Y 3+ at the Al 3+ sublattice inferred spectroscopically, 7,8 consistent with theo...

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Drastic Ce3+ Insertion Enhancement in YAG Garnet Nanocrystals Through a Solvothermal Route

Cited by 9 publications

References 51 publications

Silver nanoparticles as a new sintering additive for the fabrication of YAG:Ce optical luminescent ceramics

Silver nanoparticles as a new sintering additive for the fabrication of YAG:Ce optical luminescent ceramics

Ce3+ Doped Al2O3-YAG Eutectic as an Efficient Light Converter for White LEDs

Highly Nonstoichiometric YAG Ceramics with Modified Luminescence Properties

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