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2024
ACL
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M.Cholin, C.Genevois, P.Carles, M.Allix, J.Cornette, M.Colas, F.Fayon, V.Sarou-Kanian, G.Delaizir, P.Thomas, S.Chenu, V.Couderc, J.-R.Duclère, 'Crystallization Mechanisms in New Bismuth Borotellurite Glass-Ceramics', Cryst. Growth Des. 24 4582 (2024) doi:10.1021/acs.cgd.4c00253
The molar composition 30TeO2−40B2O3−30Bi2O3 doped
with 0.5Er2O3 is explored. Starting from a homogeneous glass, new
borotellurite glass-ceramics were elaborated after a two-step heat
treatment composed of both nucleation and growth processes. The
crucial parameters, determined by differential scanning calorimetry, were
the nucleation optimal temperature and duration. The structural
modifications occurring while heating and the related microstructure
evolution were followed by ex situ X-ray Diffraction and Scanning
Electron Microscopy. Mechanisms of the partial crystallization were
investigated through Transmission Electron Microscopy observations and
local chemical analyses (Energy Dispersive Spectroscopy and Electron
Energy Loss Spectroscopy). Thus, the employed heat treatments formed
glass-ceramics composed of boron-free Bi2Te2O7 polycrystalline entities
dispersed in the boron-oxide-enriched glassy matrix. The partial crystallization happens, therefore, concomitantly with the observed
chemical demixtion, where boron oxide separates from the bismuth tellurite phase. Additionally, Raman spectroscopy and Nuclear
Magnetic Resonance data reveal that the overall BO4/BO3 ratio of the glass network does not show significant evolution during the
partial crystallization. Optical transmission and photoluminescence properties were also measured. For glass-ceramics, the optical
transmission strongly drops. Both emission and excitation spectra of Er3+ ions, as well as lifetime measurements, highlight the
modified environment around the rare-earth ions occurring with partial crystallization.
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