Browsing by Author "Sabikoglu I."
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Item Photoluminescence investigations of Li 2SiO 3:Ln (Ln=Er 3+, Eu 3+, Dy 3+, Sm 3+) phosphors(2012) Sabikoglu I.; Ayvackl M.; Bergeron A.; Ege A.; Can N.In this study, we report a comprehensive structural and photoluminescence (PL) study on lithium metasilicate (Li 2SiO 3) phosphor ceramics doped with four rare earth (RE) ions. X-ray diffraction (XRD) patterns show a dominant phase, characteristic of the orthorhombic structure Li 2SiO 3 compound and the presence of dopants has no effect on the basic crystal structure of the material. The first excited state Er 3+ luminescence at 1.54 μm arises from a sharp atomic-like radiative transition between the 4I 13/2 state and the 4I 15/2 state (ground level) under a 532 nm line of an Ar ion laser excitation. Sm doped samples showed Sm 3+ emission characteristics corresponding to the some 4G 5/2→ 6H j (j=5/2,9/2,11/2) transitions indicating a strong crystal-field effect. PL spectra of Eu doped material exhibited peaks corresponding to the 5D 0→ 7F j (j=0,1,2,3 and 4) transitions under 405 nm excitation. The dominant red color emission at 612 nm from the hypersensitive ( 5D 0→ 7F 2) transition of Eu 3+ indicates the inversion antisymmetry crystal field around Eu 3+ ion, which is favorable to improve the red color purity. Dy doped samples showed the Dy 3+ emission characteristic due to the 4F 9/2→ 6H 13/2 transition. Their relative intensity ratios also suggested the presence of a symmetric environment around the metal ion. We suggest that lithium metasilicate has enough potential candidates to be a phosphor material. © 2012 Elsevier B.V.Item Measurements of environmental pollution in industrial area using magnetic susceptibility method(Polish Academy of Sciences, 2012) Kucer N.; Sabikoglu I.; Can N.Gaziemir district of Izmir, the Aegean Free Zone, is an industry center of approximately 295 companies that operate in lots of fields such as production, maintenance-repair, trade and that provide 1/3 of total employment in 21 free zones in Turkey. In this study, magnetic susceptibility values of soil samples taking from environment of various factories in Aegean Free Zone have been determined. Magnetic susceptibilities of samples in low and high frequency have been measured by Bartington MS2B magnetic susceptibility measurement device. All of the samples have showed ferromagnetic characteristics and also their pseudosingle-domain structures and super paramagnetic granule additives have been determined by evaluating their graphics connected to frequency.Item Piezoresistive and posistor effects in polymer-semiconductor and polymer-ferropiezoceramic composites(Maik Nauka-Interperiodica Publishing, 2016) Mamedov H.A.; Parali L.; Kurbanov M.A.; Bayramov A.A.; Tatardar F.N.; Sabikoglu I.In this study, piezoresistive and posistor effects in polymer-semiconductor and polymer-ferropiezoceramic composites have been investigated. The results show that composites based on crystallizable polymers, such as PVDF, HDPE, and PP dispersed by semiconductors and ferropiezoelectric fillers have piezoresistive and posistor properties, respectively. At low pressure, charge carriers tunneling through the located thin polymer among filler particles into the barrier define the conductivity of the composite. When pressure value is increased from 0 to 1 MPa, the thickness of the interlayer decreases and tunnel conductivity descends exponentially depending on barrier height. The piezoresistor sensitivity of a composite based on PVDF-70 vol % + Si-30 vol % is higher than a composite based on HDPE-70 vol % + Ge-30 vol %. Furthermore, the posistor properties of polymer composites dispersed by ferropiezoceramic are determined as the maximum resistance that varies significantly with temperature. Posistor effect in composites based on polymer + ferropiezoceramic is associated with the height of the barrier layer, which changes according to properties of filler, polymer, and dielectric permittivity of two-phase composites. The highest specific resistance related to HDPE-70 vol % + BaTiO3-30 vol % composite was observed at ~403 K. © 2016, Pleiades Publishing, Ltd.Item Calibration of gamma-ray detectors using Gaussian photopeak fitting in the multichannel spectra with a LabVIEW-based digital system(Institute of Physics, 2017) Schlattauer L.; Parali L.; Pechousek J.; Sabikoglu I.; Celiktas C.; Tektas G.; Novak P.; Jancar A.; Prochazka V.This paper reports on the development of a gamma-ray spectroscopic system for the (i) recording and (ii)rocessing of spectra. The utilized data read-out unit consists of a PCI digital oscilloscope, personal computer and LabVIEW™ programming environment. A pulse-height spectra of various sources were recorded with two NaI(Tl) detectors and analyzed, demonstrating the proper usage of the detectors. A multichannel analyzer implements the Gaussian photopeak fitting. The presented method provides results which are in compliance to the ones taken from commercial spectroscopy systems. Each individual hardware or software unit can be further utilized in different spectrometric user-systems. An application of the developed system for research and teaching purposes regarding the design of digital spectrometric systems has been successfully tested at the laboratories of the Department of Experimental Physics. © 2017 European Physical Society.Item Energy harvesting sensor - PZT0,5M0,5(M:PVC, PP, PVDF) composite thick film equipped with SiO2(American Institute of Physics Inc., 2019) Sabikoglu I.PZT (Lead zircon titanate) material has been used for many years because of its unique piezoelectric properties especially in conversion of electrical energy to mechanical energy and vice versa, and it is the most used material in this piezoelectric area. These kinds of piezoelectric materials, which can be produced as thin or thick film, have a wide range of uses in electronics such as; ultrasonic applications, in aircraft air-flames, structural health monitoring, and in energy harvesting as actuators or transducers, due to its large surface area and flexibility. In this study, composite thick films were produced with PZT piezoelectric material by using different polymers. In addition, synthesized in nano size the SiO2 (silicon dioxide) spheres were added to the films. PZT-5H (Navy Type VI) piezoelectric materials were made into film by melting method with the different polymers (Polyvinyl chloride - PVC, Polypropylene - PP, and Polyvinylidene fluoride - PVDF). The SiO2 spheres, which have about 120nm particle size, were added to this polymer PZT films at a rate of 1%. In present study, invert microscope images and scanning electron microscope (SEM) images of the films were obtained, in addition to this, the capacitance, dielectric constant, resonance and anti-resonance frequencies and effective efficiencies were calculated with a homemade system. It can be decided that the produced films can be used as low frequency actuators or transducer in energy harvesting system. © 2019 Author(s).Item Statistical analysis and susceptibility properties of heavy/light metal pollution in surface seawater of Izmir Bay(Springer Science and Business Media Deutschland GmbH, 2021) Sabikoglu I.The inner bay of Izmir is known as the part between Sasalı/Karşıyaka coastline and Güzelbahçe/Bayraklı. It is used extensively in transportation. There is constant ferry transportation and an international port operates in this region. There are also a few streams that flow into the inner bay. Therefore, the inner bay can be exposed to continuous chemical pollutants, and these wastes can intensively be observed in its natural structure. In this study, the magnetic susceptibility values and elemental analyses of the samples taken from the surface sea waters of the inner bay coastline were performed. Silicon, strontium, and manganese elements were mostly observed in the samples. The greatest susceptibility values were seen in the Bostanlı ferry port and Göztepe ferry. In addition, the standard deviation and correlation coefficient values of the samples were calculated and discussed. According to the correlation coefficient value, it can be said that there is a positive correlation between metal ion ratios and magnetic susceptibility. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.