KSrVO4:Tb3+-A potential green-emitting nanophosphor candidate for white LEDs

The present work reports the preparation of KSr(1 - 3x/2)VO4:xTb(3+) powders (x = 0 to 5.0 mol%) via low-cost combustion route. The XRD study affirms the phase purity of the phosphors and established the nano-size of the powdered grains which is also supported by Transmission Electron Microscopy (TEM) studies. The UV-Vis spectroscopy reveals that the title phosphor has appreciable absorption efficiency in the UV excitation range from 190 to 400 nm. The optical band gap and Urbach energy, respectively, were estimated to be 3.62 eV and 100.6 meV. The photoluminescence (PL) spectra shows that under 311 nm UV excitation corresponding to 4f(8)-4f(7)5d transition of Tb3+, this phosphor exhibited the characteristic green emission with enhanced intensity which was ascribed to electric dipole transition D-5(4) -> F-7(5) of Tb3+ ion. The CIE chromaticity coordinates were used to find dominant wavelength, excitation purity and color correlated temperature (CCT) of the phosphor. The nanophosphor has potential to be explored as the green-emitting candidate for white light LEDs for reflected light illumination applications.