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Structural Characterization and Photoluminescent Properties of (La 1– x Sm x ) 2 Ti 2 O 7 Solid Solutions Synthesized by a Sol–Gel Route
Author(s) -
Shao Zhenmian,
Saitzek Sébastien,
Blach JeanFrançois,
Sayede Adlane,
Roussel Pascal,
Desfeux Rachel
Publication year - 2011
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201100309
Subject(s) - samarium , luminescence , photoluminescence , materials science , phosphor , analytical chemistry (journal) , lanthanum , crystallography , raman spectroscopy , band gap , pyrochlore , lanthanide , valence (chemistry) , titanium , ion , phase (matter) , inorganic chemistry , chemistry , physics , optoelectronics , organic chemistry , chromatography , optics , metallurgy
Abstract A series of compounds with the general formula (La 1– x Sm x ) 2 Ti 2 O 7 (0 ≤ x ≤ 1.0) has been synthesized by a sol–gel method and characterized by XRD, Raman spectroscopy, and scanning electron microscopy (SEM). These compounds are structurally isomorphic to perovskite‐type La 2 Ti 2 O 7 until a substitution rate of x = 0.8. Above this substitution rate ( x > 0.8), a biphasic mixture is obtained between the substituted perovskite layered phase and the pyrochlore Sm 2 Ti 2 O 7 phase. The unusual phosphor (La 1– x Sm x ) 2 Ti 2 O 7 has been elaborated and its luminescent properties were investigated for low rates of substitution. The emission and excitation spectra were used to study the luminescent properties. The (La 1.9 Sm 0.1 ) 2 Ti 2 O 7 powders emit bright red–orange lightunder UV excitation. The emission properties show thatLa 2 Ti 2 O 7 is a suitable host where the La 3+ ions can be substituted by other trivalent lanthanide ions that induce luminescence properties in the visible region and lead to phosphor materials. The electronic structure calculations of (La 1.9 Sm 0.1 ) 2 Ti 2 O 7 shows that this compound is an insulator with a band gap of about 2.77 eV. The valence band mainly consists of oxygen states with hybridized titanium and samarium states; whereas, the conduction band mainly consists of titanium states with hybridized lanthanum and samarium states.