Structural and luminescence properties of magnesium silico-phosphate doped with europium and dysprosium ions

Phosphor materials based on magnesium silico-phosphate was prepared via solid-state reaction method. The series of samples were in the form of xMgO (70-x) SiO230P2O5: yEu2O3, zDy2O3 with 0 = x = 30 mol %, 0 = y = 1 mol % and 0 = z = 4 mol %. The X-ray diffraction pattern confirms that the synthesized material consists of SiO2, SiP2O7, Mg2P4O12 and MgSiO3. FTIR spectroscopy was carried out to investigate the structure feature and vibrational study of phosphor material. The introduction of MgO yields the oxygen bridge like SiO-, PO-, Si-O-Si, P-O-P and Si-O-P linkages and was revealed that the hydroscopic properties from P2O5 can be reduced. Other than that MgO also take part in the formation of P=O:Mg by the breakdown of the vibration of double bond, P=O. The morphology and grain size of phosphor material was studied using SEM. It proves that doping material addition changes the morphology of host system. EDAX study was employed to give a clear evidence of doping material that had been used in this study. The photoluminescence characteristics originating of europium and dysprosium trivalent were also investigated. The addition of Dy3+ as co-dopant in the 20MgO-50SiO2-30P2O5: 1Eu2O3 shows the quenching effect in the emission spectra. The photoluminescence intensity of Eu3+ decrease gradually with the concentration of the co-dopant in the range from 1 mol% to 4 mol%. The significantly intense emission peak was obtained at 474 nm (blue), 563 nm (yellow), 585 nm (orange), and 610, 645, and 658 nm (red) for 20MgO-50SiO2-30P2O5: 1Eu2O3, 1Dy2O3. The energy absorbed by Dy3+ is transferred to Eu3+ and energy levels at each transition were provided. The transition of Eu3+, 5D0 ? 7F2 and Dy3+, 4F9/2 ? 6H13/2 are hypersensitive electronic dipole transition and greatly affected by the coordination environment which are located at low-symmetry local site. Experimental results revealed that the luminescence can be affected by crystal structure, doping material concentration and morphology

Effect of Ag nanoparticles seeding on the properties of silica spheres

In this study, the effect of seed-recrystallization on the Ag deposition onto silica sphere surfaces has been investigated. It was found that increasing the seed-recrystallization cycles resulted in higher atomic deposition at ca. 84% coverage of silica surfaces with the same mole ratio of Ag precursor characterized by the Ag/Si atomic ratio obtained by XPS analyses. The addition of straight-chain palm oil derived fatty alcohols (PODFA) in the sol-gel prior to seed-recrystallization aided the deposition of Ag. Thus, PODFA play the role of nonsurfactant surface modification agent to produce Ag-silica nanocomposite. Structural analyses showed that the resulting Ag nanocrystallines having a face centre cubic structure and particle size of 5–20 nm were deposited homogeneously on silica spheres. Chemical state analyses from XPS indicated that the increasing number of seed repetition process increased the seeding of Ag nanoparticles on silica surface with the same molar of Ag atoms. XPS spectra at O1s orbital elucidated that the binding energy of three oxides components were determined at ca. 533.8 eV (Si-O-H), 532.8 eV (Si-O-Si) and 530.8 eV (Si-O-Ag), respectively. The high sensitivity of surface plasmon resonance observed in the nanocomposites prepared in this study are useful in optical applications

Vibrational studies of calcium magnesium ultraphosphate glasses

Phosphate glasses in a system of magnesium calcium phosphate for host matrix luminescent materials were investigated. The glass samples in a series of xMgO–(40- x)CaO–60P2O5 in molar ratio (0 ? x ? 40 mol%) were prepared using melt-quenching technique. The effect of Mg and Ca content on the structure and glass stability against crystallization in the system of MgO–CaO–P2O5 ultraphosphate has been investigated using XRD, Infrared and Raman spectroscopy. The compositions containing up to 40 mol% of CaO and /or MgO formed glasses and no crystalline phases were detected by XRD. The results of IR and Raman spectroscopy suggest that the phosphate network of these glasses is composed of middle (Q2) and branching (Q3) phosphate tetrahedral and other calcium/magnesium anions. All the symmetric and asymmetric stretching vibrations of POP and PO2 observed in the spectra are characteristic of Q3 and Q2 groups. The glass network, especially the Q2 units can be modified by the presence of Ca and Mg ions. This modification is primarily associated with the phosphate and the Q2 and Q3 phosphate units randomly distributed in the network. Spectroscopic results shows that the modification of the phosphate network is higher for the Ca containing glasses with respect to the Mg ones, at the same alkali earth content, due to the well defined Ca properties as a modifying cation. Formation of P–O–H bond expresses the hygroscopic nature of the phosphate glasses. This study shows that the vibrational spectroscopy (Infrared and Raman) are provide useful, complementary information about the network structures of ultraphosphate glasse

Structural studies on magnesium calcium tellurite doped with Eu2+ and Dy3+

The samples of phosphor material based on alkali earth tellurite, doped with rare earth have been prepared using solid state reaction method. The samples are with the composition in mol %: xMgO-(30-x)CaO-70TeO2 with 0=x=30 mol%, and have been doped with Eu2O3(2mol%) and Dy2O3(1mol%). The structure of the samples have been investigated by means of X-Ray Diffraction, Raman and Infrared spectroscopy. The xray diffraction results show that two phase are observed in the samples, which is MgTe2O5 and CaTe2O5 phase. Raman spectroscopy studies show that the vibrations of the samples are identical with the a-TeO2 vibrations, with a shift about 40-50cm-1. Strong bands are observed located at around 435, 616, 689, 785, and 807cm-1. As the concentration of the modifier, MgO and CaO increased, the coordination of TeO4 are transform from the corner sharing, a-TeO2 structure to the edge sharing, ß-TeO2 structure. It is also indicated that the increasing of MgO contribute to the increasing of symmetry vibration of TeO4 molecule, s(TeO4), while the addition of CaO increased the asymmetry vibration of TeO4 molecule, as(TeO4). The comparison between Raman and IR spectra is also include to identify the mode vibration of the samples