Serdar Yildirim

Production, characterization, and luminescent properties of Eu3+ doped yttrium niobate–tantalate films

Monoclinic yttrium tantalate (M′-YTaO4, M′-YTO), and two different kinds of yttrium niobium-tantalate (M′-YTa0.85Nb0.15O4 (M′-YTNO) and Eu3+ doped M′-YTa0.85Nb0.15O4 (M′-YTNO:Eu3+)) were produced by sol–gel method and grown on single crystalline Si (100) substrate by spin coating approach. Structural properties and thermal behaviours of the films were characterized by means of X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and thermogravimetry and differential thermal analysis (TG–DTA). Systematic Steady-state photoluminescence and lifetime measurements in a series of yttrium niobium-tantalate with varying amounts of Eu3+ were presented. The photoluminescence spectra of the films exhibited strong blue (380–400 nm) and red (614 nm) emissions upon ultraviolet excitation. Emission intensities were strongly dependent on the host lattice composition and film morphology. 1.5% Eu3+ doped films exhibited the brightest luminescence and long lifetime extending to 1.22 ms when excited at 254 nm. To the best of our knowledge, this is the first attempt in the production of M′-YTO, M′-YTNO, and M′-YTNO:Eu3+ films on single crystalline Si (100) substrate via sol–gel spin coating.

Effect of La 3+ and Ti 4+ Ions on the Magnetic Properties of Barium Hexaferrite Powders Synthesized Using Sol-Gel Method

Doped and undoped barium hexaferrite powders (BaFe 12 O 19 , Ba 0.7 Ti 0.3 Fe 12 O 19 and Ba 0.7 La 0.3 Fe 12 O 19 ) were produced by the sol-gel method. The effects of substituting elements were studied in terms of the magnetic properties of barium hexaferrite powders. The magnetic properties were remarkably changed by the substitution of La 3+ and Ti 4+ ions for the Ba 2+ ion and were accompanied by oxygen deficiency in the BaFe 12 O 19 . Coercivities (HC) from 4200 to 5100 Oe, remanences (MR) from 22 to 49 emu/g and saturation magnetizations (MS) from 41 to 73 emu/g were obtained for different samples. The obtained results were discussed in detail.

Dielectrical, optical, and structural characterization of TiO 2 /PVA nanocomposite films for dielectric applications

In this study, titanium dioxide/poly(vinyl) alcohol (TiO2/PVA) nanocomposite thin films were prepared by a simple spin-coating method for dielectric applications. Structural, morphological, optical, and dielectric properties of samples were analyzed by XRD, SEM, AFM, UV-VIS, and dielectric measurements. The effect of TiO2 nanoparticles on these properties was investigated. It was found that TiO2 nanoparticles lead to increase the crystallinity of nanocomposites. As TiO2 content in the composite structure increases, while average transmittance values decrease, reflectance values increase. The dielectric parameters such as real and imaginary part of complex permittivity which are related to the stored energy and the dissipation (or loss) of energy were significantly affected by the presence of TiO2 nanoparticles. In addition, alternating current (A.C.) conductivity increased with increasing applied frequency. The A.C. conductivity also confirmed that all the samples exhibited the insulator behavior and obeyed the universal power law.

Fabrication and characterization of Gd2O2SO4:Tb3+ phosphors by sol-gel method

The objective of the innovative approaches of the scintillation materials to be used in the digital portal imaging systems in the radiotherapy applications is to research the GOS material production that has been activated with the rare earth elements (RE), to produce the scintillation detectors that have a rapid imaging process with a lesser radiation and higher image quality from these materials and to apply the radiographic imaging systems. The GOS: Tb3+ showed high emission peak and high x-ray absorption properties which have been determined for application to mammography and dental radiography. In this study, Gd2O2SO4:Tb3+ phosphors were fabricated by the sol-gel method that is a unique technique and not previously applied. Besides, the structural characterization of GOS: Tb3+ has been investigated. The strongest emission peak located at 549 nm under 312 nm UV light excitation was appeared on the GOS: Tb3+ phosphor particles. The characterization processing optimized by using FTIR, DTA-TG, XRD, XPS, ...