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The study deals with the use of different amounts of MgO or tetraethyl orthosilicate (C 8 H 20 O 4 Si, TEOS), from 0.04 wt %, 0.06 wt %, 0.08 wt %, 0.4 wt %, 0.6 wt % to 0.8 wt %, respectively, as additional sintering aids during the vacuum sintering of transparent Ce3+ doped Y 3 Al 5 O 12 (Ce:YAG) ceramics to investigate their effect on microstructure and luminescence properties. A comparative study was carried out by using X - ray diffraction, scanning electron microscopy/energy dispersive X - ray spectroscopy, optical and photo-luminesce spectra, as well as electroluminescent spectra. The dominant garnet phase was obtained even when adding 0.8 wt % of MgO or TEOS, while adding MgO led to finer average grain size (∼ 5 - 10 μm) and more homogenous distribution compared to TEOS (∼ 20 - 25 μm) in Ce:YAG ceramics. Adding a large amount of MgO was found to result in the segregation of MgO in Ce:YAG ceramics, while an excess of TEOS led to the segregation of Al 2 O 3. A strong absorption peak at 308 nm was observed in Ce:YAG ceramics with MgO sintering aids, which was ascribed to the existence of Ce4+ induced by a charge compensation effect of Mg2+. The optimum transmittance reached 80% @ 800 nm in Ce:YAG ceramics when adding 0.6 wt % TEOS, which also exhibited a maximum luminous efficacy of 106 lm/W. Si4+ was experimentally proved to have a better optimization effect on luminous efficacy compared to Mg2+. • MgO or TEOS (C 8 H 20 O 4 Si) was added as additional sintering aids in a wide amount range. • MgO proves to have distinct inhibit effect on the grain growth. • Better luminous efficacy were observed in ceramics with TEOS additives. [ABSTRACT FROM AUTHOR]

Molybdates have applications in various fields such as phosphors, optical fibers, scintillators, magnets, sensors and catalysts. Thulium ion is an excellent blue activator and plays an important role in the design of persistent luminescent materials. This paper reports the investigation of the structural and luminescent properties of Barium Thulium Molybdate (Ba 1− x Tm x )MoO 4 microcrystals (with x = 0, 0.01 or 0.03). The scheelite-type crystalline structure was identified from XRD and Raman studies. Under ultraviolet (359 nm) excitation, photoluminescence (PL) spectra present the characteristic emission bands at 453 nm and 545 nm which are due to the D 1 2 → F 3 4 and D 1 2 → H 3 4 , 5 transitions, respectively, from Tm 3+ ions. Thermoluminescence (TL) measurements were performed with powdered samples previously irradiated with beta radiation. The depth of traps, associated with trap levels located inside the band-gap, was determined from TL data using different methods of glow curve analysis. The kinetic parameters, determined from thermoluminescent glow curves, provide evidence about a possible persistent luminescence emission from the (Ba 0.97 Tm 0.03 )MoO 4 sample. This is a potential blue-light or ultraviolet long-lasting phosphor, with a trapping level lifetime, at room-temperature (300 K), of about 6 days. [ABSTRACT FROM AUTHOR]

Excellent properties of optical ceramics initially developed as laser materials make them attractive for scintillator applications. The effects of the porosity of ceramics on their luminescence properties is analyzed using a simplified model to account for scattering. The results of the study of optical and luminescence properties of a concentration series of YAG:Yb ceramics fabricated by vacuum sintering and nanocrystalline technology (VSN method) in a wide UV and VUV and X-rays excitation energy range are presented. The results are compared to those obtained for Yb-doped single crystals and undoped YAG ceramics and single crystals. [ABSTRACT FROM AUTHOR]

Technology of producing single crystal scintillators is rather a hard and complex technological task connected with a very low output issue (15-50%) of the material and the restricted area of its application. Recent efforts of scientists are directed toward searching for alternative ways for producing these materials. It was established that high-performance ceramic scintillation materials for producing the scintillators could be prepared by using powder metallurgy techniques. However despite of certain achievements in this area, transparency of ceramic scintillators is still under the question. In our opinion a key to the solution of the problem lies in preparing scintillators in nanocrystalline structural state. A technology developed on the basis of the modified Sol-Gel method shows possibilities of manufacturing number of standard (as well as new hard to obtain as single crystals) scintillation materials. Present work is dedicated to the problems of manufacturing yttrium orthosilicate (Y2SiO5 )—as of one of the perspective scintillation materials. [ABSTRACT FROM AUTHOR]

The temperature dependence (from -20 to +20 degrees C) of gamma-ray irradiated light outputs, energy resolutions, and decay time profiles of three YAG:Ce poly-ceramic scintillators are studied. The Ce concentrations are 0.5, 0.05, and 0.005 mol%. The relative light yield of the YAG:Ce with 0.5 mol% with a 2 μs shaping time was measured as 1 : 1.08 : 1.14 at +20, 0, and -20 degrees C, respectively, including the temperature dependence of the phototube (-0.2 %/degree). The energy resolution stays almost constant at 7.2% for 662 keV gamma-rays. The ceramic with 0.05 mol % shows the almost same properties, while the light yield of that with 0.005 mol% is 2–4 times lower (hence the energy resolution becomes 14–19%). All the scintillators exhibit good linearities within ∼ 1% between the light output and the irradiated gamma-ray energy from 59.5 keV to 662 keV. The decay time constants of the dominant decay components are about 80 ns and 300 ns at +20 degrees C. As the temperature increases from -20 to +20 degrees C, the effective decay of all the ceramics becomes faster, because the decay time constants and fractions of the slower components shorten and decrease, respectively. This result suggests that carriers which are captured in shallow traps before transferring excitation to Ce ions can escape the traps more easily at higher temperatures. Considering the decrease of the total light yield toward higher temperatures, it is thought that thermal quenching starts to dominate the temperature dependence of the ceramic YAG:Ce around the room temperature. The 0.5 mol% scintillator shows a lower quenching energy than the 0.05 mol% one. This can be explained in terms of self absorption of Ce emission. [ABSTRACT FROM AUTHOR]

Describes a scintillator based on a transparent ceramic of Lu[sub2]O[sub3]:Eu. Imaging performance of the pixelated scintillator; Advantages offered by transparent optical ceramics (TOC) for scintillator applications over powder screens; Overview of TOC preparation and properties.