Browsing by Author "Kaynar, H"

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    Phase transition and luminescence characteristics of dysprosium doped strontium stannate phosphor synthesized using hydrothermal method
    Kaynar, H; Coban, MB; Madkhli, AY; Ayvacikli, M; Can, N
    A series of strontium stannate (SrSnO3) doped with Dy3+ ions at various wt % concentrations (1, 2, 3 and 5) were synthesized via hydrothermal reaction and analysed using X-ray diffraction (XRD), energy dispersive spectros-copy (EDS), environmental electron scanning microscope (ESEM), photoluminescence (PL) and, cath-odoluminescence (CL). The XRD results confirmed that all samples were assigned to cubic perovskite-type SrSnO3 structured with the Pm3m space group. The PL emission spectrum of Dy3+ activated samples consisted of some characteristic peaks located at 481 nm, 572 nm, 660 nm and 753 nm, corresponding to (4F9/2 -> 6H15/2, blue), (4F9/2 -> 6H13/2, yellow), 660 nm (4F9/2 -> 6H11/2, red) and 753 nm (4F9/2 -> 6H9/2, red) transitions. The PL emission line intensity is gradually enhanced with an increase in doping concentration up to 3 wt %, followed by concentration quenching. The confinement effects of localized resonant energy transfer might cause higher concentration quenching. PL emission spectra were affected by the temperature range from 10 K to 300 K. PL emission anomalies at 270 K in SrSnO3:Dy3+ have been reported to be consistent with a structural phase tran-sition at this temperature. This work confirms Singh et al.'s observation, revealing that SrSnO3 has a phase transition at 270 K.
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    Thermoluminescence kinetic parameters of beta irradiated the zinc gallate phosphor using different methods
    Altowyan, AS; Sonsuz, M; Kaynar, H; Hakami, J; Ayvacikli, M; Topaksu, M; Can, N
    The ZnGa2O4 phosphor material was synthesised through the gel combustion method, and its structural characteristics were studied via X-ray powder diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). The XRD result indicates the generation of ZnGa2O4 in spinal cubic phase with a 25 nm crystalline size. The synthesized phosphor was irradiated using a90Sr/90Y source with a dose range of 0.1 Gy-100 Gy. For measuring thermoluminescence (TL), a linear heating rate of 2 degrees Cs  1 was applied to the sample in a temperature range of 25 degrees C-450 degrees C. The TL experiment revealed two peak maxima located at 180 degrees C and 304 degrees C and a shoulder around 70 degrees C. By preheating at 110 degrees C, the low temperature peak at 70 degrees C is removed. Both the depth and frequency factors of electron traps were determined using various heating rates (VHR), Tm-Tstop combined with initial rise (IR), and Computerised Glow Curve Deconvolution (CGCD). In both the Tm-Tstop and CGCD methods, six overlapping glow peaks were detected below the main glow peaks. The calculated activation energy values and peak maximum temperatures agree well with each other. The depths of electron traps calculated by different methods were found to be between 0.4 and 1.4 eV. We observed that both peak maximum temperatures and the area under glow peaks gradually decreased with an increase in the heating rate. Both Peak 1 and Peak 2 show sublinear relationship between 0.1-5Gy and 10-100 Gy. The findings of the present study show that the phosphors can serve as effective TLDs.
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    Prevalence and Risk Factors of Allergies in Turkey (PARFAIT): results of a multicentre cross-sectional study in adults
    Kurt, E; Metintas, S; Basyigit, I; Bulut, I; Coskun, E; Dabak, S; Deveci, F; Fidan, F; Kaynar, H; Uzaslan, EK; Onbasi, K; Ozkurt, S; Karakis, GP; Sahan, S; Sahin, U; Oguzulgen, K; Yildiz, F; Mungan, D; Yorgancioglu, A; Gemicioglu, B; Kalyoncu, AF
    The Prevalence and Risk Factors of Allergies in Turkey (PARFAIT) study was planned to evaluate the prevalence of and risk factors for asthma and allergic diseases in Turkey. The present analysis used data from 25,843 parents of primary school children, obtained from a cross-sectional questionnaire-based study. A total of 25,843 questionnaires from 14 centres were evaluated. In rural areas, the prevalences asthma, wheezing, allergic rhinitis and eczema in males were: 8.5% (95% confidence interval (CI) 7.9-9.1%), 13.5% (95% Cl 12.8-14.2%), 17.5% (95% Cl 16.7-18.2%) and 10.8% (95% Cl 10.2-11.4%), respectively; and in females were: 11.2% (95% Cl 10.9-11.8%), 14.7% (95% Cl 14.3-15.1%), 21.2% (95% Cl 20.4-22.0%) and 13.1% (95% Cl 12.4-13.8%), respectively. In urban areas, the corresponding prevalences in males were: 6.2% (95% Cl 5.8-6.6%), 10.8% (95% Cl 10.3-11.3%), 11.7% (95% Cl 11.4-12.0%) and 6.6% (95% Cl 6.2-7.0%), respectively; and in females were: 7.5% (95% Cl 7.9-7.1%), 12.0% (95% Cl 11.7-12.3%), 17.0% (95% Cl 16.4-17.6%) and 7.3% (95% Cl 6.9-7.7%), respectively. Having an atopic first-degree relative or any other atopic diseases had significant effects on the prevalence of allergic diseases. Housing conditions, such as living in a shanty-type house, visible moulds at home and use of wood or biomass as heating or cooking material were associated with one or more allergic diseases. Although genetic susceptibility is strongly associated, country- and population-based environmental factors may contribute to increased prevalence rates of allergic diseases.
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    Prevalence and risk factors of allergies in Turkey: Results of a multicentric cross-sectional study in children
    Kurt, E; Metintas, S; Basyigit, I; Bulut, I; Coskun, E; Dabak, S; Deveci, F; Fidan, F; Kaynar, H; Uzaslan, EK; Onbasi, K; Ozkurt, S; Pasaoglu, G; Sahan, S; Sahin, U; Oguzulgen, K; Yildiz, F; Mungan, D; Yorgancioglu, A; Gemicioglu, B; Kalyoncu, AF
    The Prevalence And Risk Factors of Allergies in Turkey (PARFAIT) study was planned to evaluate prevalence and risk factors of asthma and allergic diseases and also to find out which geographical variables and/or climatic conditions play a role determining the prevalence of allergic diseases in Turkish school children. Study was planned as cross-sectional questionnaire-based. About 25,843 questionnaires from 14 centers were appropriate for analysis. Parental history of allergy, having an atopic sibling and other atopic disease in index case was significant risk factors for all allergic diseases. Breast feeding decreased the risk of current asthma (OR: 0.92, CI: 0.86-0.99) and wheezing (OR: 0.93, CI: 0.87-0.99) but not allergic rhinitis and eczema. Respiratory infection in the past was an important risk factor for the occurrence of allergic diseases especially for asthma which was increased 4.53-fold. Children exposed to household smoke were significantly at higher risk of asthma, wheezing, and allergic rhinitis (OR: 1.20, CI: 1.08-1.33; OR: 1.21, CI: 1.09-1.34; and OR: 1.32, CI: 1.21-1.43, respectively). All allergic diseases were increased in those children living in areas which have altitude of below 1000 m and mean yearly atmospheric pressure above 1000 mb. The study has suggested that household and country-specific environmental factors are associated with asthma, wheezing, allergic rhinitis, and eczema risk during childhood in Turkey.
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    Structural and temperature dependence luminescence characteristics of RE (RE=Eu3+, Dy3+, Sm3+and Tb3+) in the new gadolinium aluminate borate phosphor
    Madkhali, O; Kaynar, H; Alajlani, Y; Coban, MB; Guinea, JG; Ayvacikli, M; Pierson, JF; Can, N
    GdAl3(BO3)4:Dy3+, Sm3+, Eu3+, and Tb3+ samples were successfully achieved via a sol-gel combustion method. The observed XRD analysis confirms the formation of the desired GAB host, indicating rhombohedral structures that agree well with JPCD card number 72-1985. The FTIR analyses show the detection of B -O stretching and B -O -B bending modes as well as Al -O and Gd -O bonds in the phosphor samples. Energy dispersive spectroscopy (EDS) analysis reveals that Sm, Eu, Dy, and Tb have been successfully doped into GdAl3(BO3)4. The observed broad intrinsic luminescence band can be caused by oxygen-induced luminescence defects in the GAB host with hydrous precursors. The luminescence properties of rare earth ion-doped GdAl3(BO3)4 samples are analysed by photoluminescence spectra, showing their optimal doping concentrations and critical distances of Dy3+, Eu3+, Sm3+ and Tb3+ are 2 wt% -25.8 angstrom, 7 wt% -17 angstrom, 1 wt% -32.59 angstrom, and 7 wt% -17.03 angstrom. Additionally, the energy transfer mechanism for luminescence quenching was determined as dipole-dipole (for Dy3+, Eu3+, and Tb3+) or dipole-quadrupole (for Sm3+) and the cross-relaxation process. GdAl3(BO3)4 samples obtained by doping with different RE3+ ions exhibit intense light emissions with different colors originating from different RE3+ ions under 349 nm excitation. When doped with different concentrations of RE3+ ions, the luminescence properties of the samples changed. The synthesized luminescence materials have potential ap-plications in lighting and display technologies.