SPIE Journal Paper | 10 September 2018
KEYWORDS: Ytterbium, Europium, Ions, Perovskite, Crystals, Barium, Strontium, Calcium, Energy transfer, Absorption
This paper reports photoluminescent studies of ATiO3 : Eu2 + , Yb2 + (A = Ca, Ba, Sr) perovskites synthesized by facile molten salt synthesis (MSS) technique. This synthesis technique uses fused salt NaCl to create an active reaction medium. The perovskites were synthesized at a sintering temperature of 950°C with the doping concentration of Eu2 + and Yb2 + ions varying from 0 to 2 mol. %. The study of crystallographic analysis set forth the orthorhombic, tetragonal, and cubic crystal structures of CaTiO3 : Eu2 + , Yb2 + ; BaTiO3 : Eu2 + , Yb2 + ; and SrTiO3 : Eu2 + , Yb2 + perovskites, respectively, with appreciable phase purity and homogeneity. The field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) micrographs show agglomerated globules with the average diameter varying from 180 to 360 nm. The UV–visible absorption spectra of synthesized phosphors show a number of peaks centered between 450 and 550 nm with increased absorbance count confirming the efficient energy transfer between Eu2 + and Yb2 + ions. The Fourier transform infrared (FTIR) spectral analysis shows peaks around 500 to 750 cm − 1 corresponding to bridging stretching modes of Ti–O–Ti. The sharp peaks in the range of 990 to 1260 cm − 1 were characteristics of asymmetrical stretching of Eu2 + and Yb2 + impurity ions. The active vibrational modes of A–O were obtained in range of 1460 to 1680 cm − 1. The photoluminescence emission spectra of ATiO3 : Eu2 + , Yb2 + (A = Ca, Ba, Sr) perovskites (1:1 mol. %) phosphor exhibits emissions at 460, 480, 500, 530, 550, 560, 585, 600, and 645 nm, which are resultants of efficient energy transfer and crystal field splitting influenced hypersensitive transitions of Eu2 + ions and Yb2 + ions. The sensitization-based efficient energy transfer between Eu2 + and Yb2 + ions results in increased lumen output of the codoped perovskite phosphors. The analysis of chromaticity parameters confirms the color tunability of the synthesized perovskite phosphors.
