Silicates luminescence propertie

Prehnite is sheet silicate with orthorhombic structure (mm2). Luminescence properties of prehnite have not been studied. The natural prehnite in our study consisted of two samples. The laser-induced time-resolved technique enables us to detect emission center Pb (Fig. 4.23). 

LUMINESCENCE PROPERTIES OF CuInSe Te i x) NANOPARTICLES IN SILICATE GLASSES... 

Deposition-precipitation with urea has been also used to prepare Eu doped-YjOj/silica materials (39), which find application not in catalysis, but in the field of phosphor emitting in fluorescent lamps and cathode ray tubes. The method has been applied for depositing yttria (9.7 wt %) doped with Eu (0.30 wt %) from a mixture of nitrates heated at 80°C in the presence of urea and silica for 90 min. After thermal treatment at 900°C, YjOj particles are 12 nm large, coated by a silicate, and after thermal treatment at 1000°C, the a-YjSijO, phase forms. It exhibits interesting luminescent properties, and the authors conclude that this method of preparation is more promising than the sol-gel method. 

Zhang X, Wang J, Huang L, Pan E, Chen Y, Lei B, Wu M (2015) Tiinable luminescent properties and concentration-dependent site preferable distribution of Eu ions in silicate glass for white LEDs applications. ACS Appl Mater Inbafaces... 

In this chapter, we will first summarize the binary oxyhalide phosphors represented by Sr40Cl6 Eu phosphor then the main topic is focused on the ternary oxyhalide-based phosphors such as halo-silicate phosphors, halo-phosphate phosphors, halo-borate phosphors, halo-aluminate phosphors, and other oxyhalide-based phosphors systems. Finally, we sum up the representative work on crystal-structure and luminescence-property studies for the oxyhalide-based phosphors in oiu group. 

Except for the previously mentioned halo-silicate, halo-phosphate, halo-borate, and halo-aluminate phosphors, there are also other interesting halo-containing phosphors such as the following halo-sulphate [105-107] and halo-nitride [108, 109] compounds. Study of the crystal chemistry, synthesis technique, and luminescence properties will be very important. 

According to different host materials, long-persistent phosphors are divided into sulfide, oxysulfide, aluminates, and silicate phosphors, etc. In the next paragraphs, we introduce the luminescent properties of these long-persistent phosphors. 

The luminescence properties of trivalent lanthanide ions in rare earth silicate matrices are quite well known. Most materials studied include oxyortho-, di-, halo-and alkali double silicates of yttrium, lanthanum, gadolinium and lutetium. 

Red colour is produced in rare earth phosphors by Eu activators. In rare earth silicates the emission intensity of bivalent europium seems to be weak (McAllister, 1969). Shiokawa and Adachi (1979) have activated the rare earth siUcates with divalent europium and found the typical emission colour of Eu " -activated phosphors blue or blue-green. Blasse and Bril (1967a) have studied the luminescence properties of Eu +-activated MRSiQ4 (M = Li, Na) (fig. 54). In all compounds the orange transition Dq Fj had the highest intensity. The fluorescence spectra have been used as a structural probe and the crystallographical position of the activator ion has been predicted from the sharpness and number of the emission peaks. 

Copeland T.S., Lee B.I., Qi J., Elrod A.K. Synthesis and luminescent properties ofMn +-doped zinc silicate phosphors by sol-gel methods. J. Lumin. 2002 97 168-173 De G., Karmakar B., Ganguli D. Hydrolysis-condensation reactions of TEOS in the presence of acetic acid leading to the generation of glass-like silica microspheres in solution at room temperature. J. Mater. Chem. 2000 10 2289-2293... 

Rare earth silicates exhibit potential applications as stable luminescent materials for phosphors, scintillators, and detectors. Silica and silicon substrates are frequently used for thin films fabrication, and their nanostructures including monodisperse sphere, NWs are also reliable templates and substrates. However, the composition, structure, and phase of rare earth silicates are rather complex, for example, there are many phases like silicate R2SiOs, disilicate R2Si207 (A-type, tetragonal), hexagonal Rx(Si04)602 oxyapatite, etc. The controlled synthesis of single-phase rare earth silicate nanomateriais can only be reached with precisely controlled experimental conditions. A number of heat treatment based routes, such as solid state reaction of rare earth oxides with silica/silicon substrate, sol-gel methods, and combustion method, as well as physical routes like pulsed laser ablation, have been applied to prepare various rare earth silicate powders and films. The optical properties of rare earth silicate nanocrystalline films and powders have been studied. 

With silicon there are formed the silicide ZrSi2, the natural silicate ZrSiO, and various complex silicates. Native zircon as well as certain other zirconium ores are quite strongly radioactive, and when heated they display luminescence and suffer a change in density and color. Zircon also shows2 the property of triboluminescence. 

The synthesis, structural characterization and luminescence spectroscopy studies of AV-5 and AV-9 (Aveiro microporous solids no. 5 and 9), the first examples of microporous framework cerium(III) and europium(III) silicates (Na4K2X2Sii6O3gT0H2O, X = Eu, Ce) are reported. Both materials display interesting photoluminescence properties and present potential for applications in optoelectronics. This work illustrates the possibility of combining in a given framework silicate microporosity and optical activity. 

The final section Part IV is concerned with physical properties of polymeric nanocomposites (PNCs). Two types of nanoparticles, leading to two different characters and applicabilities of PNC, are discussed layered silicates (with natural or synthetic clays), used in structural-type PNCs and the others used in functional PNCs. Sender et al. in Chapter 13 describe the performance of PNCs with acicular ferroelectric particles producing PNCs with good electroactive (dc conductivity) and mechanical properties. In Chapter 15, Nicolais and Carotenuto focus on metal clusters in polymeric matrices, which combine optical transparency with magnetism, luminescence. Ultraviolet-visible absorption, thermochromism, and so on. 

The abundance of (oxo)nitrido(alumino)silicates thus makes it possible to develop phosphors with different emission colors. Eu " and Ce " are obviously the two most used dopants in luminescent (oxy)nitrides because their 4/—> 5d emissions are broad, highly efficient, and stmcture-dependent. The optical properties of Eu " - and Ce -doped (oxy)nitrides reported are summarized in Tables 16.3 and 16.4. In this section, we will provide an overview of nitride luminescent materials suitable for white-LED applications. 

The main focus of research on the rare earth silicates has been their preparation and structure. A summary of the structural data available is presented in table 14. In many cases the physical properties are unknown. An important application of the rare earth silicates is the use of yttrium oxyorthosilicate activated with terbium as a luminescent material in fluorescent lamps. Several patents have been published in this field. 

Modes S., Lianos P. Structural study of silicate glasses by luminescence probing The nature of small semiconductor particles formed in glasses. Chem. Phys. Lett. 1988 153 351-356 Momose F., Matsunaga K., Matsui K., Semura S., Kyoto M., Shida A. Photophysical and photochemical properties ofRu(bpy)j in Si-Ti mixed oxides xerogels prepared by the sol-gel process. J. Sol-Gel Sci. Tech. 2002 23 79-83... 

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