Structural and luminescence characterization of red-emitting Li6SrLa2Nb2O12:Eu3+ phosphors with excellent thermal stability

Abstract

Eu3+ doped Li6SrLa2Nb2O12 phosphors were synthesized and XRD patterns for the representative samples revealed its single phase structure. The Rietveld refinements indicate Li6SrLa2Nb2O12:Eu3+ samples crystallized in the cubic structure with Ia-3d space group. The optical band gaps of Li6SrLa2Nb2O12 calculated by the diffuse reflectance spectra (3.75 eV) were in very good agreement with the density functional theory (3.59 eV). Monitored at 609 nm, the phosphor showed serials of sharp peaks originated from f-f transitions of Eu3+ ions from 350 nm to 500 nm. Under 394 nm excitation, the Li6SrLa2Nb2O12:Eu3+phosphor showed red photoluminescence band centered at about 609 nm because of 5D0→7F2 transition of Eu3+ ions. The Li6SrLa2Nb2O12:0.4Eu3+sample exhibits the internal quantum yield as high as 51.3% and the color coordinates of this sample were calculated to be (0.6443, 0.3554) with high color purity of 98.9%. Particularly, the phosphor has excellent luminescence thermal stability, maintaining 82.25% of the room temperature emission intensity at 423 K. All the results confirmed that Li6SrLa2Nb2O12:Eu3+ samples have strong potential for NUV w-LEDs.