Esra Öztürk

Luminescence properties of M2TiO4:Eu3+, Li+ (M:Mg, Ca) and MgAl2O4:RE3+ (RE3+:Ho3+, Sm3+, and Yb3+)

In this study, we aimed to prepare perovskite-related and Eu3+-activated Mg2TiO4, Ca2TiO4 and (Mg, Ca)2TiO4 doped with Eu3+, Li+, and spinel-oxide-type MgAl2O4 doped with Ho3+, Sm3+, and Yb3+ through a solid-state reaction method under open atmosphere. The thermal behaviors of the samples were characterized by DTA/TG. The phase properties were characterized by X-ray diffraction and the effects of rare-earth ions (Eu3+, Ho3+, Sm3+, and Yb3+) on the luminescence properties of the hosts were investigated using a photoluminescence spectrometer. The morphology and elemental analysis of each sample were determined by SEM/EDX.

MgAl2Si2O8:Mn4+ Systems Doped with Co-Activator for Optoelectronic Applications

Mn4+ doped and Pr3+,4+, Sm3+, Gd3+, Tb3+,4+, Ho3+, Er3+, Tm3+ and Yb3+ co-doped MgAl2Si2O8-based phosphors were prepared by conventional solid state synthesis at 1300 °C. They were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray powder diffraction (XRD), photoluminescence (PL) and scanning electron microscopy (SEM). The luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 600-715 nm and had a different maximum intensity when activated by UV illumination, was discussed. Such a red emission can be attributed to the intrinsic 2E→4A2 transitions of Mn4+.

The effect of Ba/Mg impurities on the phase formation and photoluminescence properties of (Sr3−xMx)Al2O6:Eu3+,Ho3+ (M = Ba, Mg) phosphors

The Eu3+-activated strontium aluminate-based Sr3Al2O6:Eu3+,Ho3+, Sr2.99Ba0.01Al2O6:Eu3+,Ho3+ and Sr2.99Mg0.01Al2O6:Eu3+,Ho3+ phosphor systems were prepared by the solid-state reaction method under open atmosphere. DTA/TG analysis was conducted to obtain the thermal behaviours of the phosphors. Depending on the thermal analysis results, the heat treatments were carried out and the obtained single phase formations were characterised by X-ray diffraction. The effects of Ba2+ and Mg2+, which were individually added as trace amounts, and also of the same activator (Eu3+) and co-dopant (Ho3+) that were used for all host lattices, on the photoluminescence and phase formation properties of the hosts were investigated.

Fabrication of MgAl2Si2O8 : M0.01 (M = Ni2+, Cu2+, Pd2+, Pt2+ and Ru3+): catalytic effects for the reduction of 2- or 4-nitroanilines in water

Five new MgAl2Si2O8 : M0.01 (M = Ni2+, Cu2+, Pd2+, Pt2+ and Ru3+) materials were developed for the reduction of nitroarenes as catalysts by conventional solid state reaction at 1300∘C. The prepared materials were characterized by thermal analysis, Fourier transform infrared spectroscopy, X-ray powder diffraction analysis, scanning electron microscopy, energy-dispersive X-ray analysis and nitrogen adsorption–desorption analysis. The catalytic activities of the prepared catalysts were tested in the reduction of 2- or 4-nitroanilines in aqueous media at ambient temperature in the presence of NaBH4 by UV–vis spectrophotometer. Furthermore, the MgAl2Si2O8 : M0.01 catalysts can be recovered by filtration and reused for five cycles for the reduction of 2-nitroaniline. These results show that the MgAl2Si2O8 : M0.01 catalysts can be used in practical applications in the reduction of nitroanilines.

The Effect of Ligand-To-Eu3+ Charge-Transfer Transitions (Lmct) on the Photoluminescence Intensity of M2sio4: Eu3+ (M = Ca, Zn) Type Phosphors

Abstract In this study, silicate systems, M2SiO4 (M = Ca, Zn) were produced by solid state reaction and doped with 1 mol% Eu3+ rare-earth ion. Their heat treatments, which were conducted at 1200 °C and above for minimum 3 hours under an open atmosphere, were applied according to the DTA/TG results. Powder X-ray diffraction XRD analyses were performed to determine the phase properties of the phosphor systems after the sintering process. It was proved that the structures of two of the phosphor systems were well formed in except that the Zn2SiO4 had some ZnO secondary phases. The expected photoluminescence (PL) results were presented and the transitions of the Eu3+ ions were observed for both phosphors.

Eu 3+ - and Ho 3+ -doped Ba 3 Al 2 O 6 - and MgAl 2 O 4 -type phosphors and their photoluminescent properties

The aluminate hosts were basically activated with the Eu3+- and Ho3+-ions which were prepared by solid-state reaction in this study. The DTA/TG results were used as a reference for the heat treatments of the samples. The Ba3Al2O6:Eu3+, Ho3+ phosphor was well indexed to the expected phase, and MgAl2O4:Eu3+, Ho3+ could not be indexed as single phase by powder X-ray diffraction analysis to the any major phase in spite of repeated and increased heat treatments for this system. Thus, MgAl2O4 and MgO impurities were obtained. Noteworthy photoluminescent results were obtained since the transitions of Eu3+-ions occurred for both of the samples.

Dy3+-activated M2SiO4 (M = Ba, Mg, Sr)-type phosphors

The alkaline orthosilicates of M2SiO4 (M = Ba, Mg, Sr) activated with Dy3+ and co-doped with Ho3+ are prepared through conventional solid-state method, i.e., mixing and grinding of solid form precursors followed by high-temperature heat treatments of several hours in furnaces, generally under open atmosphere and investigated by X-ray diffraction (XRD) to get phase properties and photoluminescence (PL) analysis to get luminescence properties. The thermal behaviours of well-mixed samples were determined by differential thermal analysis (DTA)/thermogravimetry (TG). The PL spectra show that the 478 and 572 nm maximum emission bands are attributed, respectively, to 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions.

Comparison of MgAl 2 Si 2 O 8 :Mn 4+ systems doped with co-activator ions in terms of long lifetime for optoelectronic applications

Mn⁴⁺ doped and Pr^3+,4+, Sm³⁺, Gd³⁺, Tb^3+,4+, Ho³⁺, Er³⁺, Tm³⁺ and Yb³⁺ co-doped MgAl₂Si₂O₈-based phosphors were prepared by conventional solid state synthesis at 1300 °C. They were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray powder diffraction (XRD), photoluminescence (PL) and scanning electron microscopy (SEM). The luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 600-715 nm and had a different maximum intensity when activated by UV illumination, was discussed. Such a red emission can be attributed to the intrinsic ²E→⁴A₂ transitions of Mn⁴⁺.