Sintering effects in Na-substituted Bi-(2212) superconductor prepared by a polymer method

In this study, Na-substituted Bi2Sr2Ca0.9Na0.1 Cu2O superconductor samples were prepared by a polymer solution method. Three different sintering temperatures (850, 860, and 870 °C) were used to study the effect of Na substitution. The samples have been characterized using X-ray diffraction, scanning electron microscopy (SEM), DC electrical resistivity, and DC magnetic measurements. Magnetoresistivity measurements have shown a broadening of the superconducting transition under magnetic field which is explained on the basis of the thermally activated flux flow (TAFF) model. The calculated flux pinning energies of the samples varied from 0.17 to 0.02 eV by means of increasing magnetic field 0 to 9 T. The upper critical magnetic field Hc2(0) and the coherence length ( ζ(0)) at T = 0 K were calculated using the resistivity data. Hc2(0) and ξ(0) values have been calculated as 194, 144, and 139 T and 15.5, 15.2, and 13 Å at 850, 860, and 870 °C, respectively. TAFF model has shown Bi2Sr2Ca0.9Na0.1Cu2O8+y flux pinning energies are 0.015 eV at 9 T in all cases, while they were 0.165, 0153, and 0.149 eV at 0 T for samples sintered at 850, 860, and 870 °C, respectively.This work is supported by the Research Fund of Çukurova University, Adana, Turkey, under grant contracts no. FEF2013YL18.Peer Reviewe

A systematic study on luminescence characterization of lanthanide-doped BeO ceramic dosimeters

This work aimed to investigate the luminescent characteristics of lanthanide and alkali metal ion-doped BeO ceramic pellets prepared using the co-precipitation synthesis technique for Optically Stimulated Luminescence (OSL) dosimetry applications. In this study, BeO nano phosphor was doped with lanthanides (Ln(3+)) Eu3+, Ce3+, Nd3+, Yb3+, Er3+, Gd3+, Tb3+, Tm3+, Sm3+, Pr3+, and Dy3+ and co-doped with Na+, and characterized using radioluminescence (RL), thermoluminescence (TL) and OSL techniques. Lanthanides introduced as dopants not only affected the luminescence centers but also changed the luminescence mechanisms. The RL spectra of lanthanide-doped BeO samples showed that they mostly possess dominant emissions in the narrow bands (between 200 and 450 nm) in the UV region. OSL emission bands were found to be located between similar to 250 and similar to 390 nm. The results have demonstrated that the incorporation of appropriate Ln(3+) and alkali metal ion dopants and their optimum concentrations enhanced the luminescence intensity of undoped BeO. The studied BeO:Na-5%,Ce-0.01%,Er-0.01%, BeO:Na-5%,Ce-0.005%,Tb-0.05%, and BeO:Na-5%,Ce-0.01%,Dy-0.01% ceramics can be regarded as highly sensitive controllable luminescence dosimeters. The range of sensitivity of those samples is such that their most probable use in clinical therapy dosimetry rather than in health physics. (C) 2021 Elsevier B.V. All rights reserved

Structural and magnetic properties of the Zn 0.8-4xHo xO y (0.05 ? x ? 0.10) compounds prepared by solid state reactions

Zn 0.8-4xHo xO y (0.05 ? x ? 0.10) diluted magnetic semiconductors were prepared by the solid state reaction method. We have studied the structural properties of the samples by using the XRD, SEM, and EDX techniques. The SEM results clearly demonstrate that Ho 3+ ions are quite well substituted for Zn 2+ in the ZnO lattice, and the grains of the samples are very well connected to each other and tightly packed. From the XRD and EDX spectra of the samples, it has been concluded that the substitution of Ho causes no change in the hexagonal wurtzite structure of ZnO. According to our M-H and M-T measurements paramagnetism has been observed for all the samples from our attainable lowest temperature of 10 K to 300 K. Furthermore, the trend of the AC-susceptibility (?) versus temperature curves, measured under an AC-magnetic field of 10 Oe, also support our conclusion about the paramagnetic contribution in the Zn 0.8-4xHo xO y compounds explored in this study. In order to clearly see the paramagnetic contribution, and whether there is also a ferromagnetic or antiferromagnetic contribution or not the inverse susceptibility (1/?) against temperature curves are also plotted. Those curves indicate that, the substitution of Ho into the ZnO compound causes, in addition to the paramagnetism, a weaker antiferromagnetic (AFM) interaction. © 2012 Elsevier Masson SAS. All rights reserved.The author is very much thankful to Professor Kerim Kıymaç and Res. Asst. Mustafa Akyol of the Department of Physics, University of Cukurova. This work is supported by the Research Fund of Çukurova University, Adana, Turkey , under grant contracts no. AMYO2011BAP3

Effect of reducing agent and surfactant on the morphology, structural and magnetic properties of Ni magnetic nanoparticles

We report the effect of reducing agent and surfactant on the morphology, structural and magnetic properties of Ni magnetic nanoparticles (MNPs) synthesised by the polyol process. The samples in this work were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). The XRD results indicate that samples synthesised by EG-NaOH and 1.2H-OAm/OAc have a cubic structure with space group Fm- (Formula presented.) m. The average crystallite sizes of these samples are found to be ~ 20.7 and 16.2 nm, respectively. The sample synthesised by a combination of EG-OAm/OAc grows in nanorod form, whereas that synthesised by EG-NaOH and 1.2H-OAm/OAc has a spherical shape. The temperature dependence of the magnetisation, (M-T) measurements, indicate that the EG-NaOH sample has a superparamagnetic transition, while the 1.2H-OAm/OAc sample shows ferromagnetic behaviour in the temperature range of 5–380 K. The magnetic anisotropy constants of the EG-NaOH and 1.2H-OAm/OAc samples extracted from the M-T experiments, are 141.3 × 105 and 10.5 × 105 erg/cm3, respectively. In addition, the magnetic hysteresis measurements taken at 5 and 300 K show that the 1.2H-OAm/OAc sample is more stable than the sample synthesised by EG-NaOH. The overall results are important for the use of the Ni MNPs for low- and room-temperature applications in bio- and nano-technology. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.Çukurova ÜniversitesiThis work was supported by the Çukurova University (Adana/Turkey) under the Project No. of FYL-2017-7998

Superconductivity of Bi1.6Pb0.4Sr2Ca3Cu4O12

The superconducting ceramics Bi1.6Pb0.4Sr2Ca3Cu4O12 have been prepared by the melt-casting method. A zero resistance temperature at 60 K has been observed. It has been found that the superconducting phase temperature Tc increases with increasing sintering temperature. The effect of Pb content on the superconductivity of the ceramic has been studied. The microstructure of the sample has been investigated by scanning electron microscopy. Phase analysis has been carried out by x-ray diffraction patterns and energy dispersive analysis through x-ray spectroscopy

Impact of small Er rare earth element substitution on magnetocaloric properties of (La0.9Er0.1)0.67Pb0.33MnO3 perovskite

In this work, the effect of Er substitution on the magnetic and magnetocaloric properties has been studied for (La0.9Er0.1)0.67Pb0.33MnO3 perovskite synthesized by the sol-gel procedure. Magnetization measurements performed as a function of both temperature and magnetic field in order to determine magnetic and magnetocaloric properties. The temperature dependence of magnetization measured under 5 mT magnetic field indicate that sample exhibits ferromagnetic (FM) to paramagnetic (PM) transition with increasing temperature. The Curie temperature (TC) decreases with Er-doping from 358 K for La0.67Pb0.33MnO3 to 349 K. From the isothermal magnetization measurements taken up to 5T around the TC in 3 K intervals, the magnetic entropy change (?SM) values of the sample have been determined for different magnetic fields. The ?SM max value has been calculated as 0.98, 1.73, 2.33, 2.85 and 3.23 Jkg-1K-1 for 1, 2, 3, 4 and 4.8 T, respectively. The type of magnetic phase transition has been determined as the second order from the slope of Arrott plots. © 2019 Elsevier B.V.This work is supported by the Research Fund of Çukurova University, Adana, Turkey , under grant contracts no. FEF2010D4

Field dependence of magnetization and dM/dH for Sm- and Gd-doped Bi1.7Pb0.3Sr2Ca2-xRExCu3O10+y compounds

WOS: 000224453100049We have performed magnetization measurements as a function of magnetic fields up to 4 kOe on Bi1.7Pb0.3Sr2Ca2-xRExCu3O10+y (RE: Gd-0.01, SM0.03), at different fixed temperatures T Sm3+ and Gd3+ substitution decreases the hole carrier concentration and hence the volume fraction of the superconducting phase

Influence of lithium-holmium co-doped on structural and electrical properties of BSCCO superconductor

Bi2Pb0.5Sr2Ca4Cu 6LixHoxOy (0.0?x?0.5) samples were prepared by doping with Li and Ho at changing ratios and using meltquenching method. Thus, the influences of different doping levels of Li and Ho on the structural and electrical properties of the BPSCCO compound have been investigated by electrical resistivity, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDX) techniques. It has been observed that, with increasing Li and Ho doping, the high-Tc Bi-(2223) phase gradually transforms into the low-T c Bi-(2212) and Bi-(2201) phases. However, It should be pointed out that these low-Tc superconducting phases are formed at all the doping levels, but increasing amount with increasing concentration of Li and Ho. Therefore, while the electrical resistivities in the normal states increase, the superconducting transition temperatures, Tc, hole concentrations, p, and the magnitudes of thermoelectric powers of all the samples decrease with increasing Li and Ho concentration x. As a result, the results suggest that with the increase in Li and Ho amount the superconductivities of all the samples are suppressed due to the destruction of the phase coherence by pair-breaking effects, or, to the hole filling mechanism with increasing x

AC-magnetic susceptibility of Dy doped ZnO compounds

Dy doped ZnO polycrystalline diluted magnetic semiconductor compounds have been prepared by the so called solid state reaction method. We have studied the M-H and AC magnetic properties of the compounds by using a PPMS magnetometer, and explored the phases and crystal structure by using a X-ray powder diffractometer. The XRD spectra of the compounds show that the substitution of Dy3+ for Zn2+ causes almost no change in the hexagonal wurtzite structure of ZnO, and the Dy3+ ions are successfully substituted into the Zn2+ site of the ZnO matrix. The magnetic measurements, M-H and ?-T, for T in the range from 10 to 300 K, show a paramagnetic behavior, including indirect antiferromagnetic couplings between some Dy3+ magnetic moments. Since the Curie-Weiss temperatures, ?, are all negative but decrease in magnitude with increasing Dy concentration. On the other hand, the calculated effective magnetic moments, µeff, per Dy3+ ion slowly increase with increasing Dy concentration, but are all very close to the free ion value of µeff, ~11.0 µB. Therefore, the trends of the magnitudes of ?s and µeff s indicate that the samples are not only paramagnetic but also have antiferromagnetic couplings due to the complex nature of the compounds. In addition, the thermal variation of average magnetic moment, Peff(T), per Dy3+ ion have been calculated, and have been found to be gradually increasing with increasing temperature and Dy concentration. © 2015 Elsevier B.V.All rights reserved.FEF2010YL53The authors are very much thankful to Professor Tezer Fırat of the Physics Department, Hacettepe University for his help during the magnetic measurements. This work was supported by Cukurova University (Adana/Turkey) under the project number of AMYO2011BAP3 and FEF2010YL53

Structural characterization and superconductivity in Bi 1.7Pb0.3-xTbxSr2Ca 3Cu4Oy. The influence of Tb-doping

Bi1.7Pb0.3-xTbxSr2Ca 3Cu4Oy compounds (0.0?×?0.1) are synthesized by using the conventional high temperature melt quenching technique to study the influence of Tb substitution on their high-Tc superconducting properties. The effects of different Tb doping levels on the superconductor structure have been investigated by electrical resistance, magnetoresistance, scanning electron micrographs, and XRD measurements. It has been observed that, with increasing Tb3+ substitution for Pb 2+ the high-Tc Bi-(2223) phase gradually transforms into the low-Tc Bi-(2212) and Bi-(2201) phases. It should be pointed out that the low-Tc superconducting phases of Bi-(2212) and Bi-(2201) are formed for all the doping levels. The data suggest that with the increasing Tb3+ doping level the superconductivity in Bi1.7Pb 0.3-xTbxSr2Ca3Cu4O y system is suppressed due to the destruction of the phase coherence by pair-breaking effects, such as magnetic. The magneto-resistance results clearly demonstrate that with increasing magnetic field first the high-T c Bi-(2223) phase gradually diminishes and almost the low-T c Bi-(2212) phase remains, however, the trends indicate that at a reasonably high magnetic field the low-Tc phase will also be destroyed and hence the superconductivity will not be observed any more, as expected