Probing crystal structure and site‐selective photo‐physical properties of various Eu 3+ ‐doped niobates

Niobates of the formula Ba 2 LaNbO 6 and BaLaM 2+ NbO 6 (M 2+  = Mg, Ca) were synthesized by the conventional solid state route. Size dependence of M‐cation on the bulk crystal structure of BaLaM 2+ NbO 6 was studied and compared with the Ba 2 LaNbO 6 compound. X‐ray diffraction study confirmed that BaLaMgNbO 6 compound has the rhombohedral ( R 3 ¯ ) crystal structure as compared to the monoclinic (I2/m) in BaLaCaNbO 6 and Ba 2 LaNbO 6 . The change in the local structure of La cation among these compounds was investigated by carrying out Photoluminescence study on 2 atom% Eu 3+ ‐doped samples. PL study of BaLaMgNbO 6 :Eu 3+ sample indicates Eu 3+ ions occupying the distorted 12‐coordinated A‐site, while in Ba 2 LaNbO 6 : Eu 3+ , Eu 3+ is present at highly symmetric octahedral B‐site. Upon excitation, the light emission of these compounds changes from reddish‐orange to red to purple in the order Ba 2 LaNbO 6 :Eu → BaLaCaNbO 6 :Eu → BaLaMgNbO 6 :Eu 3+ , due to change in Eu 3+ ‐ions site occupancy. Lifetime study also confirmed the presence of two different Eu 3+ components at two different lattice sites and their respective emission spectra were isolated by time resoled emission spectroscopy. Furthermore, this site selective lattice occupancy of Eu 3+ ions also gave various new insights about its radiative and nonradiative properties at different lattice sites. This works presents a complete structural understanding of BaLaMNbO 6 ‐based matrices and their versatile phosphor characteristics when doped with Eu 3+ ion.