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In the present work, bismuth-doped CaAl 4 O 7 phosphor powders were obtained via modified Pechini citrate process and their photoluminescence, radioluminescence and thermally stimulated luminescence properties were studied down to 20 K. At room temperature excitation in UV led to broad-band 3P 0,1 → 1S 0 Bi3+ luminescence with three maxima located in blue-green part of spectrum as well as Bi2+ emission around 760 nm assigned to the 2P 3/2 → 2P 1/2 transition. At 150 K an additional Bi3+ emission band peaking at 370 nm appeared and its intensity increased significantly upon further cooling. The presence of a few luminescent centers of Bi3+ in CaAl 4 O 7 was assigned to the presence of defects disturbing the local symmetry of activator ions. The radioluminescence spectra showed only two bands, an intense one at 760 nm clearly related to Bi2+ and a very weak component at 555 nm associated with one of the Bi3+ sites. These two emissions were also observed in the thermoluminescence of the material following its exposure to X-rays. The Bi3+ luminescence is suitably positioned to contribute the cyan color to white-LEDs. Its quantum yield is satisfactory, close to 40%. The Bi2+ 720–850 nm emission is attractive for bioimaging as it appears in the Ist biological window. • A novel bismuth-doped CaAl 4 O 7 phosphor materials have been developed. • The phosphor exhibits a complex emission originating from both Bi3+ and Bi2+ ions. • Multicomponent broad-band emission in UV–Vis arises from a few Bi3+ centers. • Bi2+ luminescence appears in the Ist biological window. • Bi2+ emission is predominant in radioluminescence and TL spectra [ABSTRACT FROM AUTHOR]

This work is dedicated to the preparation and characterization of the radio-, thermo-, and photoluminescent properties of Lu2O3:Eu and Lu2O3:Tb nanopowder (NPs) scintillators, prepared by means of hydrothermal processing, and their film analogues made of these NPs by the spin coating method. The luminescent properties of NPs and films were characterized by cathodoluminescence (CL), photoluminescence (PL), X-ray excited radioluminescence (RL), and thermoluminescence (TL) at low and high temperatures. In Lu2O3:Eu NPs and films, mostly the luminescence of Eu3+ ions occupying the C2 site of the host, with the most intensive peaks at 611.6 nm and a decay time of 1.5 ms, was observed. On the contrary, two types of Tb3+ centers in the C2 and C3i sites with the main emission lines at 542.4 and 544.0 nm and the corresponding 4f→5d excitation bands at 270 and 305 nm and decay times of t1/e = 2.17 and 3.96 ms were observed in the case of Lu2O3:Tb NPs and films. Indications were noted that Tb3+ in the C3i symmetry position was most active in the CL spectra of Lu2O3:Tb NPs and a respective film. Thermoluminescent peaks at 110 °C and 170 °C for Lu2O3:Eu NPs and at 75 °C and 120 °C in Lu2O3:Tb NPs were observed corresponding to the hole and electron traps, respectively. Significantly different onsets of temperature quenching of Eu3+ and Tb3+ luminescence in Lu2O3:Eu and Lu2O3:Tb NPs were found at ~90 °C and ~320 °C, respectively. [ABSTRACT FROM AUTHOR]

Abstract Perfectly transparent ceramics of La 0.4 Gd 1.6 Zr 2 O 7 doped with either Eu3+ or Pr3+ ions were prepared by high-temperature vacuum sintering. Results of the Rietveld structure refinement and spectroscopic properties of the ceramics are presented and discussed in details. Photoluminescence characteristics support the non-uniformity in the crystal structure of ceramics. X-ray excited luminescence of La 0.4 Gd 1.6 Zr 2 O 7 :Eu was rather inefficient and the Pr-doped ceramics showed no Pr-related radioluminescence. Instead they produced Eu3+ emission characteristic for Gd 2 O 3 :Eu phase not detected in X-ray diffraction patterns. Highlights • Structure refinement of La 0.4 Gd 1.6 Zr 2 O 7 transparent ceramics revealed non-uniformity of its crystal structure. • Photoluminescence confirmed the multisite occupancy of the activator in Eu3+/Pr3+-doped La 0.4 Gd 1.6 Zr 2 O 7 transparent ceramics. • The Eu3+ presence as well as gadolinia contamination was analyzed through photo-/radioluminescence. [ABSTRACT FROM AUTHOR]

BaHfO 3 sintered ceramic scintillators doped with various Pr concentrations (0–1 mol%) were synthesized at 1700 °C in N 2 –H 2 atmosphere. XRD, SEM and photo-luminescent techniques at various temperatures (40 K to 550 K) were employed to reveal properties of the BaHfO 3 :Pr ceramics. Results of spectroscopic investigation indicate that the luminescence is connected almost exclusively with decay of the 3 P 0 level, while the emission from 1 D 2 is hardly seen even for higher Pr 3+ concentrations. However, the intrinsic emission of BaHfO 3 matrix, related with defects or impurities, seems to compete with the emission of Pr 3+ ions. The 3 P 0 luminescence decays give time constant of about 25–32 μs in the 40–550 K range of temperatures, while the 1 D 2 decay time depends on the dopant concentration and gets shorter above 300 K for 1% specimen due to a cross relaxation process between Pr 3+ ions. [ABSTRACT FROM AUTHOR]

Review: [discussion of the properties of the broad-band luminescence around 425 nm in the temp. [ABSTRACT FROM AUTHOR]

Undoped and Bi 3+ -doped lutetium oxytungstate (Lu 2 WO 6 ) powder materials were prepared by a solid state reaction method at selected temperatures between 1000 and 1400 °C. The structural, radio- and photoluminescent properties of these materials were investigated. Upon Bi activation, red-shifts of both emission and excitation bands are observed. While a broad emission band characteristic of undoped Lu 2 WO 6 and resulting from a charge transfer transition of the tungstate group WO 6 peaks at 450 nm, the Bi 3+ -activated Lu 2 WO 6 shows a broad band emission peaking at about 510 nm. This emission can be related to the transition between excited and ground states of a deep Bi donor. The ground state of this donor corresponds to an electron-occupied Bi-level at about 0.45 eV above the top of the valence band. Both compositions generate bright radioluminescence upon X-ray excitation at low temperatures. For Lu 2 WO 6 :Bi the radioluminescence efficiency is roughly stable in the range between 10 and 250 K, while undoped Lu 2 WO 6 suffers from moderate thermal quenching above 10 K. The fraction of total radioluminescence due to Bi contribution in Lu 2 WO 6 :Bi increases from 0.19 at 10 K to 0.53 at room temperature. A simple configuration coordinate diagram is introduced in order to illustrate and describe the charge carrier recombination and light generation mechanism in these materials. [ABSTRACT FROM AUTHOR]

The sol–gel derived synthesis of TiO2 films doped with Lu2O3:Tb3+ nanocrystallites and deposited on quartz or silicon substrates has been described. Their morphology have been determined by the SEM techniques. The transmission, photoluminescence and cathodoluminescence spectra have been measured. The emission decays have been measured and lifetimes for starting nanocrystalline powders and embedded nanocrystallites have been determinated. A strong influence of TiO2 matrix on the emission properties of embedded Lu2O3:Tb3+ nanocrystallites was found. [Copyright &y& Elsevier]