The Irradiation Induced Valence Changes and the Luminescence Properties of Samarium Ions in Ba[sub 2]SiO[sub 4]

Abstract

A Sm3+ -doped normalBa2SinormalO4 phosphor was prepared by high-temperature solid-state reaction. The reduction of Sm3+ to Sm2+ was achieved by X-ray irradiation on the as-prepared normalBa2SinormalO4:normalSm3+ . With the increasing exposure time, the Sm2+ -luminescence tends to be stronger up to 10h and then saturated. The Sm2+ ions with different site symmetries formed in normalBa2SinormalO4 were observed in the emission spectra due to the normalD05→normalF07 transition and the decay curves of the D05 level at various temperatures (10–300K) . The Sm2+ at the different sites in normalBa2SinormalO4 showed different quenching temperatures. Three crystallographic sites were identified in normalBa2SinormalO4 below 150K . However, only one site was left at temperature higher than 190K . The mechanism involved in the conversion of Sm3+ to Sm2+ under X-ray irradiation was discussed on the base of the crystal structure, crystallographic site-distributions, charge compensations, the crystal field strength acting on Sm2+ , and the defects created by X-ray irradiation. The photostability of the Sm2+ was evaluated with the photobleaching by monitoring the luminescence due to the normalD05→normalF07 transitions under the excitation of 488nm Ar+ laser. The results in this report give some necessary information for its possible applications for optical storage devices.

Effects of Postannealing on the Photoluminescence Properties of Coprecipitated Nanocrystalline BaFCl:Sm3+

“…It appears that the photoluminescence spectrum for samples annealed at 100 °C presents mainly four broad emission lines, at 559, 594, 639, and 701 nm, that can be assigned to the 4 G J − 6 H J transitions of Sm 3+ ions. 18 These lines are identical to those observed for the as-prepared nanocrystalline BaFCl:Sm 3+ without annealing at elevated temperatures. 5 After annealing at 200 °C, narrow peaks at 687 and 727 nm due to the 5 D 0 − 7 F 0 and 5 D 0 − 7 F 2 transitions of Sm 2+ ions, 19 respectively, can be observed.…”

“…Figure displays the room temperature photoluminescence spectra of nanocrystalline BaFCl:Sm 3+ annealed at temperatures between 100 and 900 °C in air. It appears that the photoluminescence spectrum for samples annealed at 100 °C presents mainly four broad emission lines, at 559, 594, 639, and 701 nm, that can be assigned to the 4 G J – 6 H J transitions of Sm 3+ ions . These lines are identical to those observed for the as-prepared nanocrystalline BaFCl:Sm 3+ without annealing at elevated temperatures .…”

Photoluminescence and Cathodoluminescence Properties of Nanocrystalline BaFCl:Sm3+ X-ray Storage Phosphor

“…As follows from Figure a, four broad emission lines at 559, 595, 639, and 701 nm are observed in the spectrum of the nanocrystalline sample at 293 K before X-irradiation. These lines, or groups of lines, can be assigned to the f – f transitions 4 G 5/2 – 6 H 5/2 , 4 G 5/2 – 6 H 7/2 , 4 G 5/2 – 6 H 9/2 , and 5 G 5/2 – 6 H 11/2 that are typical of Sm 3+ ions . In comparison with the nanocrystalline sample, the 4 G J – 6 H J emission lines of Sm 3+ ions are red-shifted by ∼3 nm in the microcrystalline sample at 293 K, implying different local structures of Sm 3+ ions in the two samples.…”

“…Because the Sm 3+ and Sm 2+ ions display very different emission spectra, luminescence spectroscopy can be utilized for the characterization of the oxidation state, the crystallographic sites, and the local coordination environment of samarium ions in the host lattice . Huang et al have demonstrated X-irradiation-induced valence changes of samarium ions in LiBaB 9 O 15 , Ba 3 BP 3 O 12 , and Ba 2 SiO 4 and identified different crystallographic sites of Sm 2+ ions in the host lattice based on the temperature-dependent and nondegenerate 5 D 0 – 7 F 0 transition of Sm 2+ ions. Nogami and Suzuki reported the increase of Sm 2+ fluorescence intensity as well as the decrease of Sm 3+ intensity by increasing the X-irradiation period in an Al 2 O 3 –SiO 2 glass.…”

A New Lamellar Gold Thiolate Coordination Polymer, [Au(m-SPhCO2H)]n, for the Formation of Luminescent Polymer Composites

“…The lifetime shortening could be attributed to thermal quenching. This results from thermal activation of the nonradiative decay pathways [32,33].…”