Visible light emitting Ln3+ ion (Ln=Sm, Eu and Dy) as a structural probe: A case study with SrZrO3

Undoped and various rare earth ion doped SrZrO3 (SZO) perovskite based phosphors have been synthesized using the gel-combustion technique employing citric acid as a fuel. The phase purity of the sample is confirmed by the X-ray diffraction (XRD) technique. It was observed that average particle size of perovskite particle was around 100 nm. In order to probe the local structure and symmetry around lanthanide ions in SrZrO3, detailed experimental investigation has been carried out. X-ray absorption near edge fine (XANES) measurements along with their respective emission spectroscopy confirm that on doping lanthanide ion; in cases they were found to get stabilized as trivalent species. Extensive time resolved emission spectroscopy (TRES) on doped samples shows that on doping Sm3+ in SZO; an efficient energy transfer takes place and Sm3+ ions are localized both in Sr and Zr positions of SZO. PL decay time shows the presence of two life time values in case of nanocrystalline SrZrO3:Sm3+: (i) Sm3+ at Zr4+ site (τ=500 µs) and (ii) Sm3+ at Sr2+ site (τ=1.2 ms) in the ratio of 3:1. Based on TRES for europium doped sample, it was inferred that, two different types of Eu3+ ions were present in the SZO matrix. The first type was a long lived species present at relatively higher symmetric site of 'Sr2+' and the second was a short lived species present at relatively lower symmetric 'Zr4+' site which gets selectively excited at 296 nm. Dysprosium ion specifically occupies Zr4+ site only in SZO. EXAFS studies supported the TRES results.