Influence of crystalline structure on the luminescence properties of terbium orthotantalates

► Terbium orthotantalates were prepared in two different crystalline structures: I2/a and P2/a. ► XRD and Raman scattering showed that the different space groups obtained were exhibited all the 18 Raman-active modes. ► PL decay curves that the Tb3+ ions occupies only one-symmetry site in both crystallographic arrangements. ► Dominated emission of Tb3+ (5D4→7F5) is centered with a maximum intensity at 549 nm (M-type) and 543 nm (M′-type). ► Fluorescence lifetimes for M-TbTaO4 and M′-TbTaO4 were determined as 33.4 μs and 1.25 ms, respectively.