Strategy to modify intrinsic luminescence via post-annealing treatment and impurity doping in SbNb3(PO4)6

Abstract

Self-activated luminescence of a phosphor has unique advantages such as natural homogeneity, wide wavelength, without rare-earth dopant, easy preparation, etc. However, its luminescence efficiency usually is not satisfied. This work reports several strategies to modify the intrinsic luminescence intensity of SbNb3(PO4)6 synthesized via the sol–gel method. XRD measurements were conducted to verify phase formations and structural characteristics. The transition natures and band energy were determined on the basis of the optical absorption. SbNb3(PO4)6 shows a broad self-activated luminescence (400–750 nm) peaked at 485 nm. Impurity ion V5+ doping improves the intrinsic luminescence of SbNb3(PO4)6. The optimal efficiency of 31.63% was observed in 7.0 mol% V5+-doped SbNb3(PO4)6. Post-annealing of as-prepared SbNb3(PO4)6 in the air can enhance the luminescence, while, annealing in CO atmosphere deteriorates the intensity. The luminescence thermal stabilities and activation energies were evaluated via the temperature-dependent emission intensities and decay lifetimes. The intrinsic defects such as oxygen vacancies (VO••) were confirmed via XPS measurements, which exerted great influences on the emission and thermal stabilities of the emission. The abnormal blue-shift of the emission spectra was presented from 10 to 350 K. The luminescence mechanism was proposed for the self-activated emission based on the dynamic emission spectra, decay time, and multiple color centers.