CEMHTI - Conditions Extrêmes et Matériaux : Haute Température et Irradiation

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A.J.Fernández-Carrión, K.Al-Saghir, E.Veron, A.I.Becerro, F.Porcher, W.Wisniewski, G.Matzen, F.Fayon, M.Allix
Local Disorder and Tuneable Luminescence in New Sr1-x/2Al2- xSixO4 (x = 0.2, 0.4 and 0.5) Transparent Ceramics
Inorg. Chem. 56 14446-14458 (2017) [view,doi]

Eu-doped Sr1-x/2Al2-xSixO4 (x = 0.2, 0.4 and 0.5) transparent ceramics have been synthesized by full and congruent crystallization from glasses prepared by aerodynamic levitation and laser-heating method. Structural refinements from synchrotron and neutron powder diffraction data show that the ceramics adopt a 1x1x2 superstructure compared to the SrAl2O4 hexagonal polymorph. While the observed superstructure reflections indicate a long-range ordering of the Sr vacancies in the structure, 29Si and 27Al solid-state NMR measurements associated to DFT computations reveal a significant degree of disorder in the fullypolymerized tetrahedral network. This is evidenced through the presence of Si-O-Si bonds, as well as Si(OAl)4 units at remote distances of the Sr vacancies and Al(OAl)4 units in the close vicinity of Sr vacancies departing from local charge compensation in the network. Moreover, luminescence measurements reveal the co-existence of Eu2+ and Eu3+ in the samples, thereby allowing tuning of the emission color depending on the excitation wavelength. The new single-phase emitting transparent ceramics presented in this paper appear as promising materials for solid state lighting applications.