Role of La3þ ion substitution sites on the photoluminescence properties of the SrTiO3:Eu3þ phosphors

• Main Authors: Jyothi, G., Gopchandran, K.G.
• Format: Article
• Language: English
• Published: H. : ĐHQGHN 2020
• Subjects: Perovskites; Red phosphor; Substitution; Raman spectroscopy
• Online Access: http://repository.vnu.edu.vn/handle/VNU_123/89318; https://doi.org/10.1016/j.jsamd.2020.04.006
• Institution: Vietnam National University, Hanoi

The consequence of the site selective substitution of La3þ ions in modifying the local crystal structure in red emitting titanate perovskites and the resulting enhancement of the luminescence properties were investigated in two distinct series of red phosphors of Sr1-x-yLaxTiO3:yEu3þ and Sr1-x/2-yLaxTi1-x/2O3:yEu3þ. Herein, the red emission line was found sharply magnified for the substitutions at the Sr2þ sites whereas broad peaks resembling the emission from the La2O3:Eu3þ red phosphor were detected for the substitution at both Sr2þ and Ti4þ sites, in the experiment of altering substitution sites of the La3þ ions in Sr1- xTiO3:xEu3þ. The local asymmetry induced by the substitution of smaller aliovalent ions was found to enhance the luminescence properties in the phosphors with doping at the Sr2þ sites. The occupation of Eu3þ ions in an environment having La3þ ions as nearest neighbours relaxes the shielding of the 4f electrons of Eu3þ to produce a broad emission in the phosphors with double site doping. The substitution of rare earth ions at the Sr2þ sites in Sr1-x-yLaxTiO3:yEu3þ was verified by the enhancement in the intensity of the Raman modes at 184 cm 1 (TO2) and 476 cm 1 (LO2). In the case of the Sr1-x/2-yLaxTi1-x/ 2O3:yEu3þ phosphors, the presence of the substituent ions at the Ti4þ sites was confirmed by the increased intensity observed for the Raman mode at 114 cm 1 (TO1).