TY  - JOUR
AU  - Nikolić, Maria Vesna
AU  - Sekulić, D. L.
AU  - Vasiljević, Zorka Ž.
AU  - Luković, Miloljub D.
AU  - Pavlović, Vladimir B.
AU  - Aleksić, Obrad S.
PY  - 2017
UR  - https://dais.sanu.ac.rs/123456789/15993
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 US
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
SP  - 4796
EP  - 4806
VL  - 28
IS  - 6
DO  - 10.1007/s10854-016-6125-6
UR  - https://hdl.handle.net/21.15107/rcub_dais_15993
ER  - 

@article{
author = "Nikolić, Maria Vesna and Sekulić, D. L. and Vasiljević, Zorka Ž. and Luković, Miloljub D. and Pavlović, Vladimir B. and Aleksić, Obrad S.",
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 US",
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 = "4796-4806",
volume = "28",
number = "6",
doi = "10.1007/s10854-016-6125-6",
url = "https://hdl.handle.net/21.15107/rcub_dais_15993"
}

Nikolić, M. V., Sekulić, D. L., Vasiljević, Z. Ž., Luković, M. D., Pavlović, V. B.,& Aleksić, O. S.. (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 US., 28(6), 4796-4806.
https://doi.org/10.1007/s10854-016-6125-6
https://hdl.handle.net/21.15107/rcub_dais_15993

Nikolić MV, Sekulić DL, Vasiljević ZŽ, Luković MD, Pavlović VB, Aleksić OS. 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
https://hdl.handle.net/21.15107/rcub_dais_15993 .

Nikolić, Maria Vesna, Sekulić, D. L., Vasiljević, Zorka Ž., Luković, Miloljub D., Pavlović, Vladimir B., Aleksić, Obrad S., "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 .,
https://hdl.handle.net/21.15107/rcub_dais_15993 .

TY  - JOUR
AU  - Nikolić, Maria Vesna
AU  - Sekulić, D. L.
AU  - Slankamenac, Miloš
AU  - Aleksić, Obrad S.
AU  - Danninger, H.
AU  - Halwax, E.
AU  - Pavlović, Vladimir B.
AU  - Nikolić, Pantelija M.
PY  - 2013
UR  - https://dais.sanu.ac.rs/123456789/557
AB  - In this work we have analyzed the effects of Ti doping on structural and electrical properties of α-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) Å, c=13.7484(1) Å 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. [Projekat Ministarstva nauke Republike Srbije, br. III45014 i br. III43008]
PB  - Belgrade : International Institute for the Science of Sintering
T2  - Science of Sintering
T1  - Structural and electrical properties of Ti doped α-Fe2O3
SP  - 281
EP  - 292
VL  - 45
IS  - 3
DO  - 10.2298/SOS1303281N
UR  - https://hdl.handle.net/21.15107/rcub_dais_557
ER  - 

@article{
author = "Nikolić, Maria Vesna and Sekulić, D. L. and Slankamenac, Miloš and Aleksić, Obrad S. 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 α-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) Å, c=13.7484(1) Å 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. [Projekat Ministarstva nauke Republike Srbije, br. III45014 i br. III43008]",
publisher = "Belgrade : International Institute for the Science of Sintering",
journal = "Science of Sintering",
title = "Structural and electrical properties of Ti doped α-Fe2O3",
pages = "281-292",
volume = "45",
number = "3",
doi = "10.2298/SOS1303281N",
url = "https://hdl.handle.net/21.15107/rcub_dais_557"
}

Nikolić, M. V., Sekulić, D. L., Slankamenac, M., Aleksić, O. S., Danninger, H., Halwax, E., Pavlović, V. B.,& Nikolić, P. M.. (2013). Structural and electrical properties of Ti doped α-Fe2O3. in Science of Sintering
Belgrade : International Institute for the Science of Sintering., 45(3), 281-292.
https://doi.org/10.2298/SOS1303281N
https://hdl.handle.net/21.15107/rcub_dais_557

Nikolić MV, Sekulić DL, Slankamenac M, Aleksić OS, Danninger H, Halwax E, Pavlović VB, Nikolić PM. Structural and electrical properties of Ti doped α-Fe2O3. in Science of Sintering. 2013;45(3):281-292.
doi:10.2298/SOS1303281N
https://hdl.handle.net/21.15107/rcub_dais_557 .

Nikolić, Maria Vesna, Sekulić, D. L., Slankamenac, Miloš, Aleksić, Obrad S., Danninger, H., Halwax, E., Pavlović, Vladimir B., Nikolić, Pantelija M., "Structural and electrical properties of Ti doped α-Fe2O3" in Science of Sintering, 45, no. 3 (2013):281-292,
https://doi.org/10.2298/SOS1303281N .,
https://hdl.handle.net/21.15107/rcub_dais_557 .