A. Bayri - Academia.edu (original) (raw)

Papers by A. Bayri

Research paper thumbnail of Growth Mechanism, Magnetic and Electrochemical Properties of Na0.44MnO2 Nanorods as Cathode Material for Na-ion Batteries

Materials Characterization, 2015

ABSTRACT Nanorods of Na0.44MnO2 is a promising cathode material for Na-ion batteries due to their... more ABSTRACT Nanorods of Na0.44MnO2 is a promising cathode material for Na-ion batteries due to their large surface area and single crystalline structure. We report the growth mechanism of Na0.44MnO2 nanorods via solid state synthesis and their physical properties. The structure and the morphology of the Na0.44MnO2nanorods are investigated by X-ray diffraction (XRD), scanning and tunneling electron microscopy (SEM and TEM), and energy-dispersive X-ray (EDX) techniques. The growth mechanism of the rods is investigated and the effects of vapor pressure and partial melting of Na-rich regions are discussed. The magnetic measurements show antiferromagnetic phase transition at 25 K and the μeff is determined as 3.41 and 3.24 μB from the χ-T curve and theoretical calculation, respectively. The electronic configuration and spin state of Mn3 + and Mn4 + are discussed in detail. The electrochemical properties of the cell fabricated using the nanorods are investigated and the peaks in the voltammogram are attributed to the diffusion of Na ions from different sites. Na intercalation process is explained by one and two Margules and van Laar models.

Research paper thumbnail of Theoretical approach to the magnetic properties of Co(II) ion in CoL2·5H2O compound (L is 5-chloro-2-methoxybenzoate)

The magnetic moments of a Co(II) complex in a recently reported CoL2·5H2O compound (L is 5-chloro... more The magnetic moments of a Co(II) complex in a recently reported CoL2·5H2O compound (L is 5-chloro-2-methoxybenzoate, ClC6H3(OCH3)COO−) were studied by a semi-theoretical approach in the vicinity of tetragonal distortion. It was found that in order to obtain the observed temperature-dependent magnetic moments, some parameters in the magnetic Hamiltonian which are related to the geometry of the complex should be varied.

Research paper thumbnail of MS-14-P-5858 Microstructural characterization of Na0. 44MnO2 nanorods as a cathode material for Na-ion batteries

Research paper thumbnail of Na $ _ {0.44} $ MnO $ _ {2} $ nanorods as a cathode material for Na-ion batteries

Research paper thumbnail of An enhancement ZT and spin state transition of Ca3Co4O9 with Pb doping

Journal of Alloys and Compounds, 2015

We reported the structural, electrical, thermal and magnetic properties of Pb-doped Ca 3 Co 4 O 9... more We reported the structural, electrical, thermal and magnetic properties of Pb-doped Ca 3 Co 4 O 9 in the range of 300-5 K. DTA analysis showed that the stability of the Ca 3 Co 4 O 9 was increased with Pb doping. According to XRD analysis, it is found that Pb ions were successfully doped in the Ca 3 Co 4 O 9 structure. The temperature of resistivity minima, T min , increased by increasing the Pb doping level and it is seen that incommensurate spin density wave state becomes more stable with Pb doping. The enhancement of thermopower was explained that Pb doping in Ca sites caused a decrease of Co 4+ fraction such that Co 4+ ions transformed into Co 3+ or Co 2+ . The room temperature ZT value of the polycrystalline sample reaches about 16 times larger value than that of the un-doped polycrystalline sample which is the promising candidate for high temperatures in the thin film applications.

Research paper thumbnail of The high possibility of antiferromagnetic exchange interactions in dinuclear Fe(III) dithiocarbamates

Russian Journal of Physical Chemistry, 2006

ABSTRACT In this study, the possible antiferromagnetic interactions in a dinuclear entity have be... more ABSTRACT In this study, the possible antiferromagnetic interactions in a dinuclear entity have been considered. It has been realized that, if the proposed structure is a real structure, there should be antiferromagnetic interactions between the dinuclear Fe(III) ions. It is also suggested that the predicted theoretical results should be tested with additional experimental measurements

Research paper thumbnail of Long-range magnetic impurities in gamma -MnCu alloys

Journal of Physics: Condensed Matter, 1993

AbshcL y-Mn a l l v show a host of antifemmagnetic phase adnsitioiu RecenUy it has b z n suggeste... more AbshcL y-Mn a l l v show a host of antifemmagnetic phase adnsitioiu RecenUy it has b z n suggested that the alloy disorder Q -thew phase admitions by lccally adpping 'islands' of non-mllinear spin density. Practical mpcrimental studies of this passibility have previously been reponed in the litemure, employing magnetic diffuse

Research paper thumbnail of Thermal conductivity and magnetic properties of the B substituted Ca3Co4O9

Current Applied Physics, 2014

ABSTRACT In this study, we reported the effects of the boron (B) substitution into the Ca site in... more ABSTRACT In this study, we reported the effects of the boron (B) substitution into the Ca site in the Ca3Co4O9 system on the electrical, thermal and magnetic properties between 300 K and 5 K. The results indicated that the B-substitution into the system caused an increase of resistivity due to the decrease on carrier concentration. Thermal conductivity decreased for the x = 0.5 B-substituted sample and then increased with increasing the B-content. Analysis on the thermal conductivity of samples showed that the phonon–phonon interaction term is the dominant component in the total thermal conductivity for all the samples. It was found that the point defect contribution to the thermal conductivity increased by increasing the B-content. The temperature dependence of magnetic susceptibility showed a paramagnetic behavior at room temperature and ferrimagnetic behavior below 20 K for unsubstituted sample. But, the magnetization decreased in the B-substituted samples. The substitution of B into the Ca site destroyed the interlayer coupling, which resulted in the decrease of the ferromagnetic behavior. The susceptibility data was fitted using Curie–Weiss law with temperature independent term and the μeff values were calculated to be 1.42 μB and 3.89 μB for unsubstituted sample and the highest B-substitution, respectively.

Research paper thumbnail of High temperature spin state transitions in misfit-layered Ca3Co4O9

Journal of Alloys and Compounds, 2014

ABSTRACT This study reports high temperature magnetic properties of the unsubstituted one togethe... more ABSTRACT This study reports high temperature magnetic properties of the unsubstituted one together with B and Sb-substituted Ca3Co4O9 system. The measured data indicated that there is an anomaly in the magnetic susceptibility, χ, between 680 and 920 K. It is believed that this anomaly is related to a critical threshold number of the high spin Co-ions such that when this threshold number is achieved, some exchange interactions between Co3+ and Co4+ take place which causes an abrupt increase in the χ–T curve. The anomaly was further investigated with B and Sb-substitutions. It is realized that both dopants promote more Co-ions in the rock salt unit cell to high spin state.

Research paper thumbnail of Growth Mechanism, Magnetic and Electrochemical Properties of Na0.44MnO2 Nanorods as Cathode Material for Na-ion Batteries

Materials Characterization, 2015

ABSTRACT Nanorods of Na0.44MnO2 is a promising cathode material for Na-ion batteries due to their... more ABSTRACT Nanorods of Na0.44MnO2 is a promising cathode material for Na-ion batteries due to their large surface area and single crystalline structure. We report the growth mechanism of Na0.44MnO2 nanorods via solid state synthesis and their physical properties. The structure and the morphology of the Na0.44MnO2nanorods are investigated by X-ray diffraction (XRD), scanning and tunneling electron microscopy (SEM and TEM), and energy-dispersive X-ray (EDX) techniques. The growth mechanism of the rods is investigated and the effects of vapor pressure and partial melting of Na-rich regions are discussed. The magnetic measurements show antiferromagnetic phase transition at 25 K and the μeff is determined as 3.41 and 3.24 μB from the χ-T curve and theoretical calculation, respectively. The electronic configuration and spin state of Mn3 + and Mn4 + are discussed in detail. The electrochemical properties of the cell fabricated using the nanorods are investigated and the peaks in the voltammogram are attributed to the diffusion of Na ions from different sites. Na intercalation process is explained by one and two Margules and van Laar models.

Research paper thumbnail of Theoretical approach to the magnetic properties of Co(II) ion in CoL2·5H2O compound (L is 5-chloro-2-methoxybenzoate)

The magnetic moments of a Co(II) complex in a recently reported CoL2·5H2O compound (L is 5-chloro... more The magnetic moments of a Co(II) complex in a recently reported CoL2·5H2O compound (L is 5-chloro-2-methoxybenzoate, ClC6H3(OCH3)COO−) were studied by a semi-theoretical approach in the vicinity of tetragonal distortion. It was found that in order to obtain the observed temperature-dependent magnetic moments, some parameters in the magnetic Hamiltonian which are related to the geometry of the complex should be varied.

Research paper thumbnail of MS-14-P-5858 Microstructural characterization of Na0. 44MnO2 nanorods as a cathode material for Na-ion batteries

Research paper thumbnail of Na $ _ {0.44} $ MnO $ _ {2} $ nanorods as a cathode material for Na-ion batteries

Research paper thumbnail of An enhancement ZT and spin state transition of Ca3Co4O9 with Pb doping

Journal of Alloys and Compounds, 2015

We reported the structural, electrical, thermal and magnetic properties of Pb-doped Ca 3 Co 4 O 9... more We reported the structural, electrical, thermal and magnetic properties of Pb-doped Ca 3 Co 4 O 9 in the range of 300-5 K. DTA analysis showed that the stability of the Ca 3 Co 4 O 9 was increased with Pb doping. According to XRD analysis, it is found that Pb ions were successfully doped in the Ca 3 Co 4 O 9 structure. The temperature of resistivity minima, T min , increased by increasing the Pb doping level and it is seen that incommensurate spin density wave state becomes more stable with Pb doping. The enhancement of thermopower was explained that Pb doping in Ca sites caused a decrease of Co 4+ fraction such that Co 4+ ions transformed into Co 3+ or Co 2+ . The room temperature ZT value of the polycrystalline sample reaches about 16 times larger value than that of the un-doped polycrystalline sample which is the promising candidate for high temperatures in the thin film applications.

Research paper thumbnail of The high possibility of antiferromagnetic exchange interactions in dinuclear Fe(III) dithiocarbamates

Russian Journal of Physical Chemistry, 2006

ABSTRACT In this study, the possible antiferromagnetic interactions in a dinuclear entity have be... more ABSTRACT In this study, the possible antiferromagnetic interactions in a dinuclear entity have been considered. It has been realized that, if the proposed structure is a real structure, there should be antiferromagnetic interactions between the dinuclear Fe(III) ions. It is also suggested that the predicted theoretical results should be tested with additional experimental measurements

Research paper thumbnail of Long-range magnetic impurities in gamma -MnCu alloys

Journal of Physics: Condensed Matter, 1993

AbshcL y-Mn a l l v show a host of antifemmagnetic phase adnsitioiu RecenUy it has b z n suggeste... more AbshcL y-Mn a l l v show a host of antifemmagnetic phase adnsitioiu RecenUy it has b z n suggested that the alloy disorder Q -thew phase admitions by lccally adpping 'islands' of non-mllinear spin density. Practical mpcrimental studies of this passibility have previously been reponed in the litemure, employing magnetic diffuse

Research paper thumbnail of Thermal conductivity and magnetic properties of the B substituted Ca3Co4O9

Current Applied Physics, 2014

ABSTRACT In this study, we reported the effects of the boron (B) substitution into the Ca site in... more ABSTRACT In this study, we reported the effects of the boron (B) substitution into the Ca site in the Ca3Co4O9 system on the electrical, thermal and magnetic properties between 300 K and 5 K. The results indicated that the B-substitution into the system caused an increase of resistivity due to the decrease on carrier concentration. Thermal conductivity decreased for the x = 0.5 B-substituted sample and then increased with increasing the B-content. Analysis on the thermal conductivity of samples showed that the phonon–phonon interaction term is the dominant component in the total thermal conductivity for all the samples. It was found that the point defect contribution to the thermal conductivity increased by increasing the B-content. The temperature dependence of magnetic susceptibility showed a paramagnetic behavior at room temperature and ferrimagnetic behavior below 20 K for unsubstituted sample. But, the magnetization decreased in the B-substituted samples. The substitution of B into the Ca site destroyed the interlayer coupling, which resulted in the decrease of the ferromagnetic behavior. The susceptibility data was fitted using Curie–Weiss law with temperature independent term and the μeff values were calculated to be 1.42 μB and 3.89 μB for unsubstituted sample and the highest B-substitution, respectively.

Research paper thumbnail of High temperature spin state transitions in misfit-layered Ca3Co4O9

Journal of Alloys and Compounds, 2014

ABSTRACT This study reports high temperature magnetic properties of the unsubstituted one togethe... more ABSTRACT This study reports high temperature magnetic properties of the unsubstituted one together with B and Sb-substituted Ca3Co4O9 system. The measured data indicated that there is an anomaly in the magnetic susceptibility, χ, between 680 and 920 K. It is believed that this anomaly is related to a critical threshold number of the high spin Co-ions such that when this threshold number is achieved, some exchange interactions between Co3+ and Co4+ take place which causes an abrupt increase in the χ–T curve. The anomaly was further investigated with B and Sb-substitutions. It is realized that both dopants promote more Co-ions in the rock salt unit cell to high spin state.