Effect of Ho3+ ion concentration on structure and spectroscopic properties of LiPbB5O9:Ho3+ phosphor

Abstract

• LiPbB 5 O 9 :Ho 3+ phosphor is prepared by solid state reaction method. • Energy transfer in LiPbB 5 O 9 :Ho 3+ is attributed to “nearest neighboring ions”. • Color coordinates of LiPbB 5 O 9 :Ho 3+ phosphors represent greenish-yellow region. • LiPbB 5 O 9 :0.08 Ho 3+ phosphor may find application in W-LEDs. Lithium lead borate (LiPbB 5 O 9 :Ho 3+ ) phosphors doped with distinct concentrations of Ho 3+ ions were prepared by solid state reaction technique. Structural characteristics were studied from X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and FT-Raman characterizations. Spectroscopic properties were studied from UV–Vis–NIR and photoluminescence (PL) spectra. From XRD investigations, crystallite sizes were calculated from Debye-Scherrer (D-S) and William-Hall (W-H) methods. Optical energy band gaps were calculated by using Tauc's relation for direct and indirect allowed transitions. The emission spectra of LiPbB 5 O 9 :Ho 3+ phosphors were recorded by monitoring the excitation wavelength at λ exc = 397 nm. Lifetime decay curves of 5 S 2 energy level of Ho 3+ ion were studied for distinct concentrations of Ho 3+ ions. Energy transfer mechanism was investigated for LiPbB 5 O 9 :Ho 3+ phosphor. Concentration quenching was observed at 0.08 mol% of Ho 3+ concentration among various concentrations. CIE color coordinates were computed and they showed the greenish-yellow region for various Ho 3+ concentrations. The present, LiPbB 5 O 9 :0.08Ho 3+ phosphor may be useful for the greenish-yellow emitting phosphor applications.