Processing and Properties of Eu3+-Doped Transparent YAG (Y(3)Al(5)O(12)) Nanoglass-Ceramics

An Eu3+-doped novel mother glass in the K(2)O-SiO(2)-Y(2)O(3)-Al(2)O(3) (KSYA) system was prepared by the melt-quench technique. The transparent Y(3)Al(5)O(12) (YAG) glass-ceramics were derived from this glass by a controlled crystallization process. The formation of YAG crystal phase, size and morphology with the progression of heat treatment was examined by X-ray diffraction (XRD), transmission electron microscopy, field-emission scanning electron microscopy, and Fourier transformed infrared reflectance spectroscopy. The crystallite sizes obtained from XRD are found to increase with heat-treatment time and vary in the range of 35-45 nm. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of 5D(0)-> 7F(j) (j=0, 1, 2, 3, and 4) and its excitation spectra show a charge transfer band around 280 nm. From these emissions, the site symmetry in the vicinity of Eu3+ ions has been found to be C(s) or lower than C(s) in the nanoglass-ceramics. Absorption and fluorescence spectra reveal that the Eu3+ ions are entering into the YAG nanocrystals of the glass-ceramics. The present study indicates that the incorporation of Eu3+ ions into the YAG crystal lattice enhance the fluorescence performance of the nanoglass-ceramics. We believe that this work would generate new avenues in the exploration of YAG nanoglass-ceramics in particular and other glass-ceramics of very high-temperature melting crystals in general

Effects of TiO(2)-SiO(2) fillers on thermal and dielectric properties of bismuth glass microcomposite dielectrics for plasma display panel

The combined effects of TiO(2) and SiO(2) fillers on thermal and dielectric properties of new lead-free environmental friendly zinc bismuth borate, ZnO-Bi(2)O(3)-B(2)O(3) (ZBIB) glass microcomposite dielectrics have been investigated from the viewpoint of application as rear glass dielectric layer of plasma display panels (PDPs). The interaction of fillers with glass occurred during firing has also been explored by XRD, SEM and FTIR spectroscopic analyses. All the properties are found to be regulated by the covalent character (a fundamental property) of resultant microcomposite dielectrics. In this work, the co-addition of TiO(2)-SiO(2) filler to ZBIB glass is found to be more effective to adjust the required properties to employ with PD200 glass substrate in PDP technology

Synthesis and properties of glasses in the K(2)O-SiO(2)-Bi(2)O(3)-TiO(2) system and bismuth titanate (Bi(4)Ti(3)O(12)) nano glass-ceramics thereof

Glasses were prepared by the melt-quench technique in the K(2)O-SiO(2)-Bi(2)O(3)-TiO(2) (KSBT) system and crystallized bismuth titanate, BiT (Bi(4)Ti(3)O(12)) phase in it by controlled heat-treatment at various temperature and duration. Different physical, thermal, optical, and third-order susceptibility (chi(3)) of the glasses were evaluated and correlated with their composition. Systematic increase in refractive index (n) and chi(3) with increase in BiT content is attributed to the combined effects of high polarization and ionic refraction of bismuth and titanium ions. Microstructural evaluation by FESEM shows the formation of polycrystalline spherical particles of 70-90 nm along with nano-rods of average diameter of 85-90 nm after prolonged heat treatment. A minor increase in dielectric constants (epsilon(r)) has been observed with increase in polarizable components of BiT in the glasses, whereas a sharp increase in epsilon(r) in glass-ceramics is found to be caused by the formation of non-centrosymmetric and ferroelectric BiT nanocrystals in the glass matrix

Preparation and Properties of BaBiBO4-SiO2 Glasses

Glasses in the new system (100-x) BaBiBO4–xSiO2 where x = 10–50 (mol%) were prepared by the melt-quench technique. The density of the glasses increases with an increase in BaBiBO4 content because of its higher molecular mass. Tg, Td,and Ts decrease while coefficient of thermal expansion increases with the increase in BaBiBO4 content. Vis-NIR spectra reveal that with increasing melting temperature transmission of the glasses decreases due to auto thermal reduction of Bi31 to Bi0 as confirmed by transmission electron microscopy and selected area electron diffraction analyses. Fourier transform infrared reflection spectroscopic spectra of the glasses indicate the formation of BiO6, BO3, and BO4 structural units. Ferroelectric BaBiBO4 crystalline phase is obtained from these glasses by controlled heat treatment at 5801C. X-ray diffraction analysis reveals its 45–66nm crystallite size range. Whereas, the field-emission scanning electron microscopy images show the formation of polycrystalline spherical grains of 89–194nm along with single-crystalline microrods of average diameter of 0.5–1.5 mm. Dielectric constant of the glasses increases with increase in BaBiBO4 content, which is attributed to the combined effects of high polarization and ionic refraction of both Bi31 and Ba21 ions. It is shown here that BaBiBO4–SiO2 is a promising glass system for the synthesis of glass–ceramics of novel BaBiBO4 nonlinear optical crystal

Effects of nano-YAG (Y(3)Al(5)O(12)) crystallization on the structure and photoluminescence properties of Nd(3+)-doped K(2)O-SiO(2)-Y(2)O(3)-Al(2)O(3) glasses

Nd(3+)-doped precursor glass in the K(2)O-SiO(2)-Y(2)O(3)-Al(2)O(3) (KSYA) system was prepared by the melt-quench technique. The transparent Y(3)Al(5)O(12) (VAG) glass ceramics were derived from this glass by a controlled crystallization process at 750 degrees C for 5-100 h. The formation of VAG crystal phase, size and morphology with progress of heat-treatment was examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Fourier transformed infrared reflectance spectroscopy (FT-IRRS). The crystallite sizes obtained from XRD are found to increase with heat-treatment time and vary in the range 25-40 nm. The measured photoluminescence spectra have exhibited emission transitions of 4F(3/2) -> 4I(J) (J = 9/2, 11/2 and 13/2) from Nd(3+) ions upon excitation at 829 nm. It is observed that the photoluminescence intensity and excited state lifetime of Nd(3+) ions decrease with increase in heat-treatment time. The present study indicates that the incorporation of Nd(3+) ions into YAG crystal lattice enhance the fluorescence performance of the glass ceramic nanocomposites. (C) 2010 Elsevier Masson SAS. All rights reserved

Environmentally Friendly and New Generation Glasses for Plasma TV

Glass plays an important role in the manufacturing of plasma display panel (PDP), that is, plasma TV. Glass is not only used there as front and back panel substrates, but also in its several components, such as front panel transparent dielectric (TD) layer, back panel opaque or white dielectric (WB) layer, barrier rib (BR) and sealing material in between front and back panels. In all the later cases, presently PbO is used in the tune of 60-80 wt% as a glass constituent. It is, therefore, essential to replace the PbO from glass compositions due to health and environmental issues keeping their existing properties unaltered. In this paper, an overview on the available PDP glasses and some of their key properties are reported. In addition, recent development carried at this institute on environmentally friendly lead-free dielectric glasses for plasma TV is briefly described. A low softening and dielectric constant lead-free ZnO-P2O5 based glass composition was also developed for manufacturing plasma TV in consideration of costeffectiveness. We believe that this work will open up a new horizon in the plasma TV research and reduce its manufacturing cost significantly as well

Effects of SiO(2) and TiO(2) fillers on thermal and dielectric properties of eco-friendly bismuth glass microcomposites of plasma display panels

The effects of SiO(2) (amorphous) and TiO(2) (crystalline, rutile) fillers on softening point (T (s)), glass transition temperature (T (g)), coefficient of thermal expansion (CTE), and dielectric constant (E >) of zinc bismuth borate, ZnO-Bi(2)O(3)-B(2)O(3) (ZBIB) glass microcomposites have been investigated with a view to its use as the white back (rear glass dielectric layer) of plasma display panels (PDPs). The experimentally measured properties have also been compared with those of theoretically predicted values. Both the experimental and theoretical trends of these properties with added filler contents correlate very well. The interaction of fillers with glass which occurred during sintering at 560A degrees C has also been monitored by XRD and FTIR spectroscopic analyses. The microstructures and distribution of fillers in the glass matrix have been analyzed by SEM images. It is observed that the fillers have partially dissolved in the glass at the firing temperature leaving some unreacted filler as residue which results in ceramic-glass microcomposites. In consideration of the desired properties of white back of PDPs, the addition of TiO(2) filler to ZBIB glass is found to be more preferable than SiO(2) filler. The addition of 10 wt% TiO(2) filler yielded T (s), T (g), CTE and E > values of 560A degrees C, 480A degrees C, 82 x 10(-7)/K and 14 center dot 6 which are found to meet the desired values of < 580A degrees C, < 500A degrees C, < 83 x 10(-7)/K and < 15, respectively with respect to use of PD200 glass as substrate in PDP technology

Sensitized red luminescence from Bi(3+) co-doped Eu(3+): ZnO-B2O(3) glasses

Photoluminescence properties of Bi(3+) co-doped Eu(3+) containing zinc borate glasses have been investigated and the results are reported here. Bright red emission due to a dominant electric dipole transition (5)D(0) -> (7)F(2) of the Eu(3+) ions has been observed from these glasses. The nature of Stark components from the measured fluorescence transitions of Eu(3+) ions reveal that the rare earth ions could take the lattice sites of C, or lower point symmetry in the zinc borate glass hosts. The significant enhancement of Eu(3+) emission intensity by 346nm excitation ((1)S(0)->(3)P(1), of Bi(3+) ions) elucidates the sensitization effect of co-dopant. The energy transfer mechanism between sensitizer (Bi(3+)) and activator (Eu(3+)) ions has been explained. (C) 2009 Elsevier B.V. All rights reserved

Effects of Nano-LiTaO(3) Crystallization on the Dielectric and Optical Properties in Er(3+)-Doped Li(2)O-Ta(2)O(5)-SiO(2)-Al(2)O(3) Glasses

The precursor glass of LiTaO(3) nanocrystals was prepared in a new Er(3+)-doped Li(2)O-Ta(2)O(5)-SiO(2)-Al(2)O(3) system by the melt-quench technique. They were isothermally crystallized at 680 degrees C for 3-100 h to obtain nanostructured glass-ceramics. The X-ray diffraction and transmission electron microscopy confirm the nanocrystallization of LiTaO(3) (16-34 nm) yielding transparent glass-ceramics. A steep rise in the dielectric constant with the heat-treatment time is attributed to ferroelectric LiTaO(3) crystallization. Photoluminescence spectra exhibit the (4)I(13/2) -> (4)I(15/2) emission transition of Er(3+) ions at 1570 nm when excited at 984 nm. Its intensity and lifetime decrease with an increase in heat-treatment time due to concentration quenching effect