The effect of vanadium substitution on photoluminescent properties of KSrLa(PO4)(x)(VO4)(2-x):Eu3+ phosphors, a new variant of phosphovanadates

Eu3+ doped red emitting phosphors of formulae KSrLa1-y(PO4)(x)(VO4)(2-x):yEu(3+) (where x = 0, 1 and 2 and y = 0, 0.02, 0.05, 0.10 and 0.015) were synthesized by a high temperature solid state reaction route. The compounds were characterized by a powder XRD method, and a complete structure determination for KSrLa(PO4)(VO4) was carried out using the Rietveld refinement method. The compound crystallized in the rhombohedral system with space group (R (3) over barm). The structure of the compound shows that La3+ is occupied at two positions, namely, trigonal antiprism (six coordinated) and truncated hexagonal bipyramidal (10 coordinated) centres, with occupancy of 0.94 and 0.06, respectively. The effect of vanadium substitution on excitation and emission spectra of the compounds was investigated using time resolved photoluminescence spectroscopy (TRPLS). The lifetimes of D-5(0) -> F-7(2) transition were determined for all the compounds, which are in agreement with emission spectroscopic results. Judd-Ofelt analysis of the compounds clearly shows that the more polarized environment around Eu3+ in the case of the vanadate and phosphovanadate in comparison to the phosphate leads to more colour purity of the emission, when excited by UV light.