Influence of Bi3+ as a sensitizer and SiO2 shell coating as a protecting layer towards the enhancement of red emission in LnVO4: Bi3+, Eu3+ @ SiO2 (Ln=Gd, Y and Gd/Y) powder phosphors for optical display devices

Abstract Enhanced red luminescence in LnVO 4 : Bi 3+ , Eu 3+ @ SiO 2 phosphors has been improved mainly in three stages by investigating the effects of: (i) host composition (Gd, Y and Gd/Y), (ii) co-doping Bi 3+ as a sensitizer and finally (iii) SiO 2 shell coating. XRD data revealed that the produced phosphors possess crystalline, pure phase with tetragonal structure. Silica coating on phosphor particles have been characterized by SEM/EDAX, TEM, PL and with the presence Si–O–Si, Si–O vibrational modes from the FT-IR spectra. Absorption band edges due to VO 4 3− , shifted to higher wavelength with Bi-concentration, owing to the presence of Bi–O bond in addition to V–O. The emission intensities of 5 D 0 → 7 F 2 transition are stronger than 5 D 0 → 7 F 1 ; indicating the lower inversion symmetry near Eu 3+ , ions. Red emission intensity due to the efficient energy transfer from VO 4 3− to Eu 3+ via Bi 3+ ions in Y 0.949 VO 4 : Bi 3+ 0.001 , Eu 3+ 0.05 phosphor was improved significantly, i.e. 1.6 times compared to Y 0.95 VO 4 : Eu 3+ 0.05 . This was further enhanced 2.25 times by SiO 2 shell coating. Thus, Y 0.949 VO 4 : Bi 3+ 0.001 , Eu 3+ 0.05 @ SiO 2 are suggested to be a promising red phosphor for application in display devices or lighting.