Structural Characterization and Photoluminescent Properties of (La1–xSmx)2Ti2O7 Solid Solutions Synthesized by a Sol–Gel Route

Abstract

AbstractA series of compounds with the general formula (La1–xSmx)2Ti2O7 (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 La2Ti2O7 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 Sm2Ti2O7 phase. The unusual phosphor (La1–xSmx)2Ti2O7 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 (La1.9Sm0.1)2Ti2O7 powders emit bright red­–orange lightunder UV excitation. The emission properties show thatLa2Ti2O7 is a suitable host where the La3+ 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 (La1.9Sm0.1)2Ti2O7 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.