Cr6+ as the hidden key to low-temperature Pechini synthesis of YAG:Cr4+
Abstract
Cr4+-doped Y3Al5O12 (YAG:Cr4+) is widely employed in photonic devices as a saturable absorber and has recently attracted attention as an infrared gain medium. However, its synthesis typically requires annealing at high temperature (>1573 K) to achieve the oxidation of Cr3+ into Cr4+, thus limiting cost efficiency and scalability. Here, we report the first successful preparation of YAG:Cr4+ nanopowders via the Pechini process at a temperature as low as 1173 K. Structural and morphological analyses (XRD, SEM, TEM) confirm the formation of nanocrystalline YAG with homogeneous chromium incorporation. Optical spectroscopy combined with XANES unambiguously demonstrates the presence of both Cr4+ and Cr6+ ions, the latter arising from the oxidative decomposition of organics during calcination—an unprecedented observation in YAG materials. To maximize Cr4+ concentration, we explored oxidation strategies including well-known Ca2+ co-doping and more original H2O2-assisted synthesis; both of which significantly enhance tetrahedral Cr4+ luminescence. Finally, we investigated the potential of heat treatment in a reducing atmosphere for obtaining Cr4+ ions, with the aim of better understanding the possible pathways for achieving the Cr4+ oxidation state in the YAG matrix at low temperatures, leading to very promising results. The low-temperature route studied here not only reduces synthesis costs but also provides new opportunities to tailor the oxidation state of chromium in garnet-type nanomaterials, paving the way for their integration in energy-efficient optical devices.
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BibTeX
@article{thevenet2026hidden,
title = {{Cr6+ as the hidden key to low-temperature Pechini synthesis of YAG:Cr4+}},
author = {Romain Thévenet and Audrey Potdevin and François Réveret and Denis Testemale and Philippe Boutinaud and Geneviève Chadeyron},
journal = {Optical Materials},
year = {2026},
month = jul,
doi = {10.1016/j.optmat.2026.118332},
url = {https://hal.science/hal-05773048v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Cr6+ as the hidden key to low-temperature Pechini synthesis of YAG:Cr4+
AU - Romain Thévenet
AU - Audrey Potdevin
AU - François Réveret
AU - Denis Testemale
AU - Philippe Boutinaud
AU - Geneviève Chadeyron
PY - 2026
DA - 2026/07/14
JO - Optical Materials
DO - 10.1016/j.optmat.2026.118332
UR - https://hal.science/hal-05773048v1
AB - Cr4+-doped Y3Al5O12 (YAG:Cr4+) is widely employed in photonic devices as a saturable absorber and has recently attracted attention as an infrared gain medium. However, its synthesis typically requires annealing at high temperature (>1573 K) to achieve the oxidation of Cr3+ into Cr4+, thus limiting cost efficiency and scalability. Here, we report the first successful preparation of YAG:Cr4+ nanopowders via the Pechini process at a temperature as low as 1173 K. Structural and morphological analyses (XRD, SEM, TEM) confirm the formation of nanocrystalline YAG with homogeneous chromium incorporation. Optical spectroscopy combined with XANES unambiguously demonstrates the presence of both Cr4+ and Cr6+ ions, the latter arising from the oxidative decomposition of organics during calcination—an unprecedented observation in YAG materials. To maximize Cr4+ concentration, we explored oxidation strategies including well-known Ca2+ co-doping and more original H2O2-assisted synthesis; both of which significantly enhance tetrahedral Cr4+ luminescence. Finally, we investigated the potential of heat treatment in a reducing atmosphere for obtaining Cr4+ ions, with the aim of better understanding the possible pathways for achieving the Cr4+ oxidation state in the YAG matrix at low temperatures, leading to very promising results. The low-temperature route studied here not only reduces synthesis costs but also provides new opportunities to tailor the oxidation state of chromium in garnet-type nanomaterials, paving the way for their integration in energy-efficient optical devices.
SN - 0925-3467
SN - 1873-1252
ER -