NUV/blue LED excitable intense green emitting terbium doped lanthanum molybdate nanophosphors for white LED applications

摘要

Terbium doped lanthanum molybdate (La_(2-x)Tb_x(MoO_4)_3) nanocrystals were successfully synthesized by facile co-precipitation method. The powder X-ray diffractogram confirmed that the nanocrystals were crystallized in tetragonal phase with space group 14_l/a. The FTIR spectra identified the characteristic vibrational modes. The TEM analysis revealed elongated nanorod like structures of length 90-350 nm formed by oriented attachment of nano-particles of average diameter 50 nm without the aid of any shape regulating catalysts. The intense broad charge transfer band in NUV region along with sharp excitation peaks of Tb~(3+) ions in the blue region of photoluminescence excitation spectra ascertains that the prepared nanophosphors are suitable materials for NUV and blue LED based lighting applications. The possibility of energy transfer from host lattice to Tb~(3+) ions is indicated by the enhancement of charge transfer band with Tb~(3+) doping concentration in the excitation spectrum. The efficient green emission at 545 nm, on exciting in the charge transfer band (287 nm) clearly evidenced the excellent energy transfer from host to Tb~(3+) ions. The intense green emission with desirable chromaticity co-ordinates and high colour purity makes Terbium doped lanthanum molybdate nanocrystals as an efficient green phosphor for NUV/ blue LED excited WLED.