Garnet luminescence

Fig. 4.56. a-d Laser-induced steady-state luminescence spectra of garnet demonstrating Cr, Mn, and possibly Mn and V centers... 

Narrow lines at 462, 476, 482, 501 and 590 nm in the luminescence spectrum of the Ca-variety of garnet (grossular) with a relatively short decay time are not typical for traditional trivalent REE in minerals. Evidently they may be connected to visible emission of Nd (Fig. 4.57c,d), but this has to be checked. 

Garnet activated by trivalent Cr is a promising system for tunable laser appUcations and those systems have been well studied. Cr + replaces Ap" in octahedral sites with a weak crystal field. The transition involved in laser action is T2- A2, a vibrationally broadened band. At room temperature it has a maximum in the 715-825 nm range with a decay time in the 100-250 ps range depending on AE between the E and T2 levels. When the AE is maximal, narrow fines also appear from the E level. At low temperatures, when thermal activation of the T2 level is difficult, J -lines luminescence becomes dominant with the main fine at 687 nm (Monteil at al. 1988). We studied pyrope artificially activated by Cr and also found the two emission types described above (Fig. 5.26). 

A.A. Kaminskii, G. Boulon, M. Buoncristiani, B.D. Bartolo, A. Kornienko, and V. Mironov, Spectroscopy of a new laser garnet Lu3Se2Ga30i2 Nd . Intensity luminescence characteristics, stimulated emission, and full set of squared redueed-matrix elements < II > for Nd ions, Phys. Slat, sol. (a), 141,471-94(1994). 

Speghini, A., Piccinelli, F., Bettinelli, M. 2011. Synthesis, characterization and luminescence spectroscopy of oxide nanopowders activated with bivalent lanthanide ions The garnet family. Optical Materials 33 247-257. 

Fig. 9.5 Temperature dependences of threshold excitation energy for the A- and B-lasing lines, together with luminescence linewidth for the A inter-Stark transition of fine-grained garnet ceramics Nd lYsAlsO 12. Reproduced with permission from [51]. Copyright 2009, John Wiley...

Guerassimova N, Dujardin C, Gamier N, Pedrini C, Petrosyan AG, Kamenskikh lA et al (2002) Charge-transfer luminescence and spectroscopic properties of Yb " in aluminium and gallium garnets. Nucl Instmm Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip 486 278-282... 

Kamenskikh I, Dujardin C, Gamier N, Guerassimova N, Ledoux G, Mikhailin V, Pediini C, Petrosyan A, Vasil ev A (2005) Temperature dependence of the charge transfer and f-f luminescence of Yb " in garnets and YAP. J Phys Craidtais Matter 17 5587-5594... 

Additional novel particles, including nylon 66, alumina, " gold, garnet, diamond, graphite, polyaniline, and boron nitride nanosheets, and nanoparticles of low molecular weight borate esters, have been introduced to increase ionic conductivities. Boron-doped PDMS has been used as scintillators for thermal neutron detection. Nanowires of ZnO have been inserted into PDMS to give tunable, flexible antireflection layers, and ZnO has also been introduced into such polymers as quantum dots. Similarly, color-tunable luminescent... 

Kaminska A, Duzynska A, Berkowski M, Trushkin S, Suchocki A (2012) Pressure-induced luminescence of cerium-doped gadolinium gallium garnet crystal. Phys Rev B 85 155111... 

Generally, aluminate phosphors with high luminescence efficiency and excellent thermal stabilities have attracted increasing attention. Typically, Ce -doped yttrium aluminum garnet Y3Al50i2 Ce (YAG Ce ) yellow-emitting phosphor has excellent properties and is widely used to generate w-LEDs. 

Many other phosphors have been developed for w-LEDs, but the phosphors with garnet, JS-K2SO4 structures have received much more attention due to their similar stmctures with the efficient YAGiCe " and orthosilicate phosphors. However, the luminescence efficiency of these phosphors reported by now is far less than those of YAG Ce and orthosilicate phosphors. Here, another promising system, molybdate phosphor, which was first developed by Hu et al. [46], is introduced in the following text. 

In luminescence research, attention has recently shifted from the development of solid-state phosphors (in television screens) and lasers (e.g., yttrium aluminum garnet (YAG) lasers) to solution-state methods exemplified by the development of probes for bioinorganic chemistry and the development of time-resolved luminescent labelings and assays. 

Luminescence of artificial garnets activated by different emission centers, such... 

Brenier A, Suchocki A, Pedrini C, Boulon G, Made C (1992) Spectroscopy of Mn -doped calcium-substituted gadolinium gallium garnet. Phys Rev B 46 3219-3227 Brugger J, Bettiol A, Costa S et al (2000) Mapping rare earth element distribution in scheelite using luminescence. Miner Mag 64 891-903... 

Krbetschek M, Gotze J, Irmer G et al (2002) The red luminescence emission of feldspar and its wavelength dependence on K, Na, Ca-composition. Miner Petrol Miner Petrol 76 167-177 Kuck S, Hartung S, Hurling S et al (1998) Emission of octahedrally coordinated Mn in garnets. Spectrochim Acta A 54 1741-1749... 

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