TY  - JOUR
AU  - Nikolić, Maria Vesna
AU  - Sekulic, Dalibor L
AU  - Vasiljević, Zorka Z
AU  - Luković, Miloljub
AU  - Pavlović, Vladimir B
AU  - Aleksić, Obrad
PY  - 2017
UR  - http://rimsi.imsi.bg.ac.rs/handle/123456789/1097
AB  - In this work we have investigated changes in dielectric properties, electrical conductivity and complex impedance of Fe2TiO5 nanopowder compacts and bulk samples as a function of elevated temperature (room to 423 K compacts, to 443 K bulk samples), frequency (100 Hz-1 MHz) and composition (starting molar ratio of Fe2O3 and TiO2 1:1-PSB11 and 1:1.5-PSB115). XRD, SEM and TEM analysis of PSB11 and PSB115 powders obtained by a simple solid state process from starting hematite and anatase nanopowders confirmed the formation of nanostructured orthorhombic pseudobrookite with small amounts of excess hematite and rutile. The dielectric constant decreased with frequency and temperature for both compacts and bulk samples. Higher values were determined for bulk samples also reflecting the influence of sample composition. Change in the dielectric loss also reflected the influence of sample composition showing one maximum at high frequencies for compacts, and two maxima at room temperature for bulk samples. Complex impedance was analyzed using equivalent circuits and showed in the case of compacts the influence of both grain and grain boundary components, while in the case of bulk samples the dominant influence of grain boundaries. The temperature dependence of the determined grain and grain boundary resistance for compacts and grain boundary resistance for bulk samples was analyzed using the adiabatic small polaron hopping model enabling determination of activation energies for conduction, while the temperature dependence of relaxation times enabled determination of activation energies for relaxation. Changes in electrical conductivity for compacts and bulk samples followed Jonscher's power law. The change of the determined frequency constant with temperature showed that at elevated temperatures the quantum mechanical-tunneling model for the case of small polaron hopping explains the conduction mechanism occurring in both compacts and bulk samples.
PB  - Springer, Dordrecht
T2  - Journal of Materials Science-Materials in Electronics
T1  - Dielectric properties, complex impedance and electrical conductivity of Fe2TiO5 nanopowder compacts and bulk samples at elevated temperatures
EP  - 4806
IS  - 6
SP  - 4796
VL  - 28
DO  - 10.1007/s10854-016-6125-6
ER  - 

@article{
author = "Nikolić, Maria Vesna and Sekulic, Dalibor L and Vasiljević, Zorka Z and Luković, Miloljub and Pavlović, Vladimir B and Aleksić, Obrad",
year = "2017",
abstract = "In this work we have investigated changes in dielectric properties, electrical conductivity and complex impedance of Fe2TiO5 nanopowder compacts and bulk samples as a function of elevated temperature (room to 423 K compacts, to 443 K bulk samples), frequency (100 Hz-1 MHz) and composition (starting molar ratio of Fe2O3 and TiO2 1:1-PSB11 and 1:1.5-PSB115). XRD, SEM and TEM analysis of PSB11 and PSB115 powders obtained by a simple solid state process from starting hematite and anatase nanopowders confirmed the formation of nanostructured orthorhombic pseudobrookite with small amounts of excess hematite and rutile. The dielectric constant decreased with frequency and temperature for both compacts and bulk samples. Higher values were determined for bulk samples also reflecting the influence of sample composition. Change in the dielectric loss also reflected the influence of sample composition showing one maximum at high frequencies for compacts, and two maxima at room temperature for bulk samples. Complex impedance was analyzed using equivalent circuits and showed in the case of compacts the influence of both grain and grain boundary components, while in the case of bulk samples the dominant influence of grain boundaries. The temperature dependence of the determined grain and grain boundary resistance for compacts and grain boundary resistance for bulk samples was analyzed using the adiabatic small polaron hopping model enabling determination of activation energies for conduction, while the temperature dependence of relaxation times enabled determination of activation energies for relaxation. Changes in electrical conductivity for compacts and bulk samples followed Jonscher's power law. The change of the determined frequency constant with temperature showed that at elevated temperatures the quantum mechanical-tunneling model for the case of small polaron hopping explains the conduction mechanism occurring in both compacts and bulk samples.",
publisher = "Springer, Dordrecht",
journal = "Journal of Materials Science-Materials in Electronics",
title = "Dielectric properties, complex impedance and electrical conductivity of Fe2TiO5 nanopowder compacts and bulk samples at elevated temperatures",
pages = "4806-4796",
number = "6",
volume = "28",
doi = "10.1007/s10854-016-6125-6"
}

Nikolić, M. V., Sekulic, D. L., Vasiljević, Z. Z., Luković, M., Pavlović, V. B.,& Aleksić, O.. (2017). Dielectric properties, complex impedance and electrical conductivity of Fe2TiO5 nanopowder compacts and bulk samples at elevated temperatures. in Journal of Materials Science-Materials in Electronics
Springer, Dordrecht., 28(6), 4796-4806.
https://doi.org/10.1007/s10854-016-6125-6

Nikolić MV, Sekulic DL, Vasiljević ZZ, Luković M, Pavlović VB, Aleksić O. Dielectric properties, complex impedance and electrical conductivity of Fe2TiO5 nanopowder compacts and bulk samples at elevated temperatures. in Journal of Materials Science-Materials in Electronics. 2017;28(6):4796-4806.
doi:10.1007/s10854-016-6125-6 .

Nikolić, Maria Vesna, Sekulic, Dalibor L, Vasiljević, Zorka Z, Luković, Miloljub, Pavlović, Vladimir B, Aleksić, Obrad, "Dielectric properties, complex impedance and electrical conductivity of Fe2TiO5 nanopowder compacts and bulk samples at elevated temperatures" in Journal of Materials Science-Materials in Electronics, 28, no. 6 (2017):4796-4806,
https://doi.org/10.1007/s10854-016-6125-6 . .

TY  - JOUR
AU  - Nikolić, Maria Vesna
AU  - Sekulic, Dalibor L
AU  - Nikolić, Nenad
AU  - Slankamenac, Milos P
AU  - Aleksić, Obrad
AU  - Danninger, H
AU  - Halwax, E
AU  - Pavlović, Vladimir B
AU  - Nikolić, Pantelija M.
PY  - 2013
UR  - http://rimsi.imsi.bg.ac.rs/handle/123456789/657
AB  - In this work we have analyzed the effects of Ti doping on structural and electrical properties of alpha-Fe2O3. When the amount of added Ti (5 wt.% TiO2) was within the solubility degree and XRD, SEM and EDS analysis revealed a homogenous hematite structure, with lattice parameters a= 5.03719(3), c= 13.7484(1) slightly increased due to incorporation of Ti into the rhombohedral hematite lattice. Higher amounts of Ti (10 wt.% TiO2) resulted in the formation of pseudobrookite, besides hematite, confirmed by SEM and EDS analysis. Studies of electric properties in the temperature range 25-225oC at different frequencies (100-1Mz) showed that Ti doping improved electrical conductivity. Impedance analysis was performed using an equivalent circuit, showing one relaxation process and suggesting dominant grain boundary contribution.
PB  - Međunarodni Institut za nauku o sinterovanju, Beograd
T2  - Science of Sintering
T1  - Structural and Electrical Properties of Ti Doped alpha-Fe2O3
EP  - 292
IS  - 3
SP  - 281
VL  - 45
DO  - 10.2298/SOS1303281N
ER  - 

@article{
author = "Nikolić, Maria Vesna and Sekulic, Dalibor L and Nikolić, Nenad and Slankamenac, Milos P and Aleksić, Obrad and Danninger, H and Halwax, E and Pavlović, Vladimir B and Nikolić, Pantelija M.",
year = "2013",
abstract = "In this work we have analyzed the effects of Ti doping on structural and electrical properties of alpha-Fe2O3. When the amount of added Ti (5 wt.% TiO2) was within the solubility degree and XRD, SEM and EDS analysis revealed a homogenous hematite structure, with lattice parameters a= 5.03719(3), c= 13.7484(1) slightly increased due to incorporation of Ti into the rhombohedral hematite lattice. Higher amounts of Ti (10 wt.% TiO2) resulted in the formation of pseudobrookite, besides hematite, confirmed by SEM and EDS analysis. Studies of electric properties in the temperature range 25-225oC at different frequencies (100-1Mz) showed that Ti doping improved electrical conductivity. Impedance analysis was performed using an equivalent circuit, showing one relaxation process and suggesting dominant grain boundary contribution.",
publisher = "Međunarodni Institut za nauku o sinterovanju, Beograd",
journal = "Science of Sintering",
title = "Structural and Electrical Properties of Ti Doped alpha-Fe2O3",
pages = "292-281",
number = "3",
volume = "45",
doi = "10.2298/SOS1303281N"
}

Nikolić, M. V., Sekulic, D. L., Nikolić, N., Slankamenac, M. P., Aleksić, O., Danninger, H., Halwax, E., Pavlović, V. B.,& Nikolić, P. M.. (2013). Structural and Electrical Properties of Ti Doped alpha-Fe2O3. in Science of Sintering
Međunarodni Institut za nauku o sinterovanju, Beograd., 45(3), 281-292.
https://doi.org/10.2298/SOS1303281N

Nikolić MV, Sekulic DL, Nikolić N, Slankamenac MP, Aleksić O, Danninger H, Halwax E, Pavlović VB, Nikolić PM. Structural and Electrical Properties of Ti Doped alpha-Fe2O3. in Science of Sintering. 2013;45(3):281-292.
doi:10.2298/SOS1303281N .

Nikolić, Maria Vesna, Sekulic, Dalibor L, Nikolić, Nenad, Slankamenac, Milos P, Aleksić, Obrad, Danninger, H, Halwax, E, Pavlović, Vladimir B, Nikolić, Pantelija M., "Structural and Electrical Properties of Ti Doped alpha-Fe2O3" in Science of Sintering, 45, no. 3 (2013):281-292,
https://doi.org/10.2298/SOS1303281N . .

TY  - JOUR
AU  - Nikolić, Maria Vesna
AU  - Slankamenac, Milos P
AU  - Nikolić, Nenad
AU  - Sekulic, Dalibor L
AU  - Aleksić, Obrad
AU  - Mitrić, Miodrag
AU  - Ivetić, Tamara B.
AU  - Pavlović, Vladimir B
AU  - Nikolić, Pantelija M.
PY  - 2012
UR  - http://rimsi.imsi.bg.ac.rs/handle/123456789/557
AB  - The effects of Zn-doping on the dielectric behavior and electrical properties of bulk alpha-Fe2O3 have been studied. X-ray diffraction analysis revealed the presence of two phases in all samples: hematite and spinel ZnFe2O4, with the amount of spinel phase increasing with increasing Zn content. Scanning electron microscopy analysis combined with energy dispersive X-ray spectroscopy showed that the Zn-bearing phase occurred in the form of individual spinel ZnFe2O4 grains in a hematite matrix. DC conductivity was measured in the temperature range 25-225 degrees C (298-498 K). Impedance spectroscopy measurements in the same temperature range were carried out in the frequency range 100Hz to 10 MHz. Increase in the Zn content resulted in increased electrical conductivity and higher values of the dielectric constant. The resistance and capacitance of grains and grain boundaries were analyzed by modeling the experimental results using an equivalent circuit.
PB  - Međunarodni Institut za nauku o sinterovanju, Beograd
T2  - Science of Sintering
T1  - Study of Dielectric Behavior and Electrical Properties of Hematite alpha-Fe2O3 Doped with Zn
EP  - 321
IS  - 3
SP  - 307
VL  - 44
DO  - 10.2298/SOS1203307N
ER  - 

@article{
author = "Nikolić, Maria Vesna and Slankamenac, Milos P and Nikolić, Nenad and Sekulic, Dalibor L and Aleksić, Obrad and Mitrić, Miodrag and Ivetić, Tamara B. and Pavlović, Vladimir B and Nikolić, Pantelija M.",
year = "2012",
abstract = "The effects of Zn-doping on the dielectric behavior and electrical properties of bulk alpha-Fe2O3 have been studied. X-ray diffraction analysis revealed the presence of two phases in all samples: hematite and spinel ZnFe2O4, with the amount of spinel phase increasing with increasing Zn content. Scanning electron microscopy analysis combined with energy dispersive X-ray spectroscopy showed that the Zn-bearing phase occurred in the form of individual spinel ZnFe2O4 grains in a hematite matrix. DC conductivity was measured in the temperature range 25-225 degrees C (298-498 K). Impedance spectroscopy measurements in the same temperature range were carried out in the frequency range 100Hz to 10 MHz. Increase in the Zn content resulted in increased electrical conductivity and higher values of the dielectric constant. The resistance and capacitance of grains and grain boundaries were analyzed by modeling the experimental results using an equivalent circuit.",
publisher = "Međunarodni Institut za nauku o sinterovanju, Beograd",
journal = "Science of Sintering",
title = "Study of Dielectric Behavior and Electrical Properties of Hematite alpha-Fe2O3 Doped with Zn",
pages = "321-307",
number = "3",
volume = "44",
doi = "10.2298/SOS1203307N"
}

Nikolić, M. V., Slankamenac, M. P., Nikolić, N., Sekulic, D. L., Aleksić, O., Mitrić, M., Ivetić, T. B., Pavlović, V. B.,& Nikolić, P. M.. (2012). Study of Dielectric Behavior and Electrical Properties of Hematite alpha-Fe2O3 Doped with Zn. in Science of Sintering
Međunarodni Institut za nauku o sinterovanju, Beograd., 44(3), 307-321.
https://doi.org/10.2298/SOS1203307N

Nikolić MV, Slankamenac MP, Nikolić N, Sekulic DL, Aleksić O, Mitrić M, Ivetić TB, Pavlović VB, Nikolić PM. Study of Dielectric Behavior and Electrical Properties of Hematite alpha-Fe2O3 Doped with Zn. in Science of Sintering. 2012;44(3):307-321.
doi:10.2298/SOS1203307N .

Nikolić, Maria Vesna, Slankamenac, Milos P, Nikolić, Nenad, Sekulic, Dalibor L, Aleksić, Obrad, Mitrić, Miodrag, Ivetić, Tamara B., Pavlović, Vladimir B, Nikolić, Pantelija M., "Study of Dielectric Behavior and Electrical Properties of Hematite alpha-Fe2O3 Doped with Zn" in Science of Sintering, 44, no. 3 (2012):307-321,
https://doi.org/10.2298/SOS1203307N . .