... D. Luković, Institute of Technical Sciences, SASA, Belgrade, Serbia. K. Radulović, Institute ... more ... D. Luković, Institute of Technical Sciences, SASA, Belgrade, Serbia. K. Radulović, Institute of Technical Sciences, SASA, Belgrade, Serbia. D. Vasiljević Radović, IHTM-CMTM, Belgrade, Serbia. S. Savić, Institute of Technical Sciences, SASA, Belgrade, Serbia. Abstract. ...
Zinc-titanate ceramics were obtained by initial mechanical activation in a high-energy planetary ... more Zinc-titanate ceramics were obtained by initial mechanical activation in a high-energy planetary mill for 15 min followed by sintering at temperatures 900–1100 °C for 2 h. Room temperature far infrared reflectivity spectra for all samples were measured in the range 100–1200 cm−1. The same ionic oscillators were present in the measured spectra, but their intensities increased with the sintering temperature in correlation with the increase in sample density and microstructure changes. Optical parameters were determined for seven oscillators belonging to the spinel structure using the four-parameter model of coupled oscillators. Born effective charges were calculated from the transversal/longitudinal splitting.
Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese (MnO ... more Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese (MnO Aldrich 99.9%) and nickel oxide (NiO Merck, 99.5%) containing 0.5 wt% CoO and Fe2O3, was additionally mechanically activated in a high energy planetary ball mill for 5–60 min. The resulting powders were uniaxially pressed into disc shape pellets and then sintered for 60 min at 900 °C, 1050 °C and 1200 °C. Morphological changes of the obtained nickel manganite ceramics induced by mechanical activation were monitored using scanning electron microscopy, while changes in structural characteristics were followed using X-ray powder diffraction. Room temperature far infrared reflectivity spectra for all sintered samples were recorded in the frequency range between 50 cm−1and 1200 cm−1. The observed spectra for all samples showed the presence of the same oscillators, but their intensities depended on the sintering temperature and the time of mechanical acivation. Transversal and longitudinal opt...
Journal of Materials Science Materials in Electronics
Intrinsic resistivity and carrier transport parameters of sintered nickel manganite samples (NTC ... more Intrinsic resistivity and carrier transport parameters of sintered nickel manganite samples (NTC thermistor grade) were determined using a Hall effect measurement system based on the van der Pauw method. Powder mixtures composed of MnO, NiO and with small amounts of CoO and Fe2O3 were free surface energy activated by milling in an ultra fast planetary mill for 5, 15, 30, 45 and 60min. The powders were uniaxially pressed with 196MPa into discs and sintered at 1200°C for 60min. Full characterization of nickel manganite samples was done using SEM, EDS and XRD analysis. The Hall effect was measured at different temperatures (room temperature, 50, 80, 100 and 120°C) with an applied field of 0.37T and also 0.57T at room temperature. The activation energy E a (energy of conduction) and the coefficient of temperature sensitivity B 25/80, were calculated from measured resistivity values. The measured mobility, resistivity/conductivity, U-I plots, and Hall coefficients were mutually compared ...
Purpose – The purpose of this paper is to apply negative thermal coefficient (NTC) thick film seg... more Purpose – The purpose of this paper is to apply negative thermal coefficient (NTC) thick film segmented thermistors (TFSTs) in a micro-flow sensor for water. Design/methodology/approach – A TFST is printed using NTC paste based on nickel manganite. The resistance of this thermistor is measured in a climatic chamber and the resulting curves are calibrated. A micro-flow sensor is designed using a self-heated segmented thermistor. The sensing principle is based on heat loss depending on the water flow intensity through the capillary. Water flow calibration is performed. The sensor sensitivity, inertia, and stability are analyzed. Findings – The micro-flow sensor exhibits good stability, suitable sensitivity, and inertia for integral measurements of water flow. Practical implications – Advantages of a micro-flow sensor using a TFST include low energy consumption, simple measuring procedure, and passive electronics. Originality/value – This paper describes initial work on a micro-flow se...
We have combined sol-gel synthetic route with hydrothermal synthesis under autogenous pressure to... more We have combined sol-gel synthetic route with hydrothermal synthesis under autogenous pressure to obtain stable TiO2 precursor gels. The gels were mixed with organic functional additives into pastes, and deposited onto fluorine-doped tin oxide (FTO) conductive substrates (12-14 Ω/sq) using tape-casting film applicator. As deposited films were carefully dried at 60-100°C, and calcined at 400°C, resulting in porous crack-free structures. The porous films were produced in different thicknesses (2-18 μm) and used as photoactive electrodes in dye-sensitized solar cells (DSSCs). Also, we have introduced a compact passivating TiO2 layer (100-300 nm in thickness), which prevents the direct contact between the conductive oxide substrate and electrolyte, thus, increasing the current density of the operating cell. The layer was produced by spin-coating deposition of TiO2 sols, prepared by chemical procedure starting from Ti(IV) isopropoxide and triethanolamine (TEA) as complexing agent. Therma...
Nb doped BaCe0.9Y0.1O2.95 (BCY) powders were synthesized by both solid state reaction (SSR) and a... more Nb doped BaCe0.9Y0.1O2.95 (BCY) powders were synthesized by both solid state reaction (SSR) and autocombustion reaction (ACR) method to investigate how different synthesis routes influence the properties of the powders and sintered samples. The powders were uniaxially pressed and sintered at 1550 degrees C to form dense electrolyte samples. Stability of BCY in CO2 can be increased by doping with Nb, but at the same time its electrical conductivities are reduced to a certain extent. It was shown that conductivities depended on both mechanism of defect formation, lattice parameters and microstructure of the electrolytes. Finer, less agglomerated powders were obtained by the method of autocombustion. SEM analysis revealed somewhat larger average grain size of the sintered samples synthesized by the ACR method. Total electrical conductivities were determined by electrochemical impedance spectroscopy (EIS) measurements in temperature range from 550 degrees C to 750 degrees C in a wet arg...
Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese and n... more Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese and nickel oxide was additionally mechanically activated in a high energy planetary ball mill for 5-60 min in order to obtain a pure NiMn(2)O(4) phase. The as-prepared powders were uniaxially pressed into disc shape pellets and then sintered for 60 min at 1200 degrees C. Changes in the particle morphology induced by mechanical activation were monitored using scanning electron microscopy, while changes in powder structural characteristics were followed using X-ray powder diffraction. The ac impedance spectroscopy was performed on sintered nickel manganite samples at 25 degrees C, 50 degrees C and 80 degrees C. It was shown that mechanical activation intensifies transport processes causing a decrease in the average crystallites size, while longer activation times can lead to the formation of aggregates, defects and increase of lattice microstrains. The observed changes in microstructures were c...
... S. Savić 1 , D. Luković 1 , S. Vujatović 1 , D. Vasiljević-Radović 2 , K. Radulović 2 and S. ... more ... S. Savić 1 , D. Luković 1 , S. Vujatović 1 , D. Vasiljević-Radović 2 , K. Radulović 2 and S. Djurić 1 1Institute of Technical Sciences of SASA, Belgrade, Serbia and Montenegro 2Institute of Microelectronics Technologies and Single Crystals, Belgrade, Serbia and Montenegro ...
2008 26th International Conference on Microelectronics, 2008
A novel uniaxial anemometer was created using a NTC thick film segmented thermistor to measure wi... more A novel uniaxial anemometer was created using a NTC thick film segmented thermistor to measure wind speed and direction. The anemometer operated on the principle of heat loss caused by the air volume flow and air speed. A NTC segmented thermistor served as a wind sensor in the anemometer. It was self-heated by a DC constant voltage. The self-heated DC
ABSTRACT An investigation path starting from (Mn,Ni,Co,Fe)3O4 nanometric powder preparation, NTC ... more ABSTRACT An investigation path starting from (Mn,Ni,Co,Fe)3O4 nanometric powder preparation, NTC thick-film characterization, realization and optimization of new planar thermistor geometries to custom design thermistors and their application for temperature and volume airflow sensors was recently determined. The aim was to make custom designed segmented NTC thermistors printed and sintered on alumina. Two types of volume airflow sensors were formed: indirectly heated and self-heated. A pair of segmented thermistors was placed in an air guide and connected to differential branches of the Wheatstone bridge. A heater was placed in the middle between the thermistors for the indirectly heated type, while for the self-heated type the same thermistors were self-heated by a constant current source. First the thermistor responses vs. the airflow (calibration curves) were measured, and then thermistor responses in time (inertia) to fast airflow changes from the minimum to the maximum. The results obtained could be applied in air conditioning for air guide flow regulation.
... MV Nikolic,1 N. Obradovic,2,5 KM Paraskevopoulos,3 TT Zorba,3 SM Savic,2 and MM Ristic4 UDC 6... more ... MV Nikolic,1 N. Obradovic,2,5 KM Paraskevopoulos,3 TT Zorba,3 SM Savic,2 and MM Ristic4 UDC 621.762 ... In this paper, changes in the structure of Zn2TiO4 due to doping with small amounts of MgO have been studied by x-ray diffraction and infrared reflection spectroscopy. ...
... PM Nikoli 1 ,* , S. Ðuri 1 , KM Paraskevopoulos 2 , TT Zorba 2 , D. Lukovi 1 , S. Savi 1 , V.... more ... PM Nikoli 1 ,* , S. Ðuri 1 , KM Paraskevopoulos 2 , TT Zorba 2 , D. Lukovi 1 , S. Savi 1 , V. Blagojevi 3 and MV Nikoli 4 ... We would like to acknowledge D. Stojanovi , who provided the crystals for far-IR measurements, Dr Chris Hayward, Associate Editor, Prof. ...
... D. Luković, Institute of Technical Sciences, SASA, Belgrade, Serbia. K. Radulović, Institute ... more ... D. Luković, Institute of Technical Sciences, SASA, Belgrade, Serbia. K. Radulović, Institute of Technical Sciences, SASA, Belgrade, Serbia. D. Vasiljević Radović, IHTM-CMTM, Belgrade, Serbia. S. Savić, Institute of Technical Sciences, SASA, Belgrade, Serbia. Abstract. ...
Zinc-titanate ceramics were obtained by initial mechanical activation in a high-energy planetary ... more Zinc-titanate ceramics were obtained by initial mechanical activation in a high-energy planetary mill for 15 min followed by sintering at temperatures 900–1100 °C for 2 h. Room temperature far infrared reflectivity spectra for all samples were measured in the range 100–1200 cm−1. The same ionic oscillators were present in the measured spectra, but their intensities increased with the sintering temperature in correlation with the increase in sample density and microstructure changes. Optical parameters were determined for seven oscillators belonging to the spinel structure using the four-parameter model of coupled oscillators. Born effective charges were calculated from the transversal/longitudinal splitting.
Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese (MnO ... more Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese (MnO Aldrich 99.9%) and nickel oxide (NiO Merck, 99.5%) containing 0.5 wt% CoO and Fe2O3, was additionally mechanically activated in a high energy planetary ball mill for 5–60 min. The resulting powders were uniaxially pressed into disc shape pellets and then sintered for 60 min at 900 °C, 1050 °C and 1200 °C. Morphological changes of the obtained nickel manganite ceramics induced by mechanical activation were monitored using scanning electron microscopy, while changes in structural characteristics were followed using X-ray powder diffraction. Room temperature far infrared reflectivity spectra for all sintered samples were recorded in the frequency range between 50 cm−1and 1200 cm−1. The observed spectra for all samples showed the presence of the same oscillators, but their intensities depended on the sintering temperature and the time of mechanical acivation. Transversal and longitudinal opt...
Journal of Materials Science Materials in Electronics
Intrinsic resistivity and carrier transport parameters of sintered nickel manganite samples (NTC ... more Intrinsic resistivity and carrier transport parameters of sintered nickel manganite samples (NTC thermistor grade) were determined using a Hall effect measurement system based on the van der Pauw method. Powder mixtures composed of MnO, NiO and with small amounts of CoO and Fe2O3 were free surface energy activated by milling in an ultra fast planetary mill for 5, 15, 30, 45 and 60min. The powders were uniaxially pressed with 196MPa into discs and sintered at 1200°C for 60min. Full characterization of nickel manganite samples was done using SEM, EDS and XRD analysis. The Hall effect was measured at different temperatures (room temperature, 50, 80, 100 and 120°C) with an applied field of 0.37T and also 0.57T at room temperature. The activation energy E a (energy of conduction) and the coefficient of temperature sensitivity B 25/80, were calculated from measured resistivity values. The measured mobility, resistivity/conductivity, U-I plots, and Hall coefficients were mutually compared ...
Purpose – The purpose of this paper is to apply negative thermal coefficient (NTC) thick film seg... more Purpose – The purpose of this paper is to apply negative thermal coefficient (NTC) thick film segmented thermistors (TFSTs) in a micro-flow sensor for water. Design/methodology/approach – A TFST is printed using NTC paste based on nickel manganite. The resistance of this thermistor is measured in a climatic chamber and the resulting curves are calibrated. A micro-flow sensor is designed using a self-heated segmented thermistor. The sensing principle is based on heat loss depending on the water flow intensity through the capillary. Water flow calibration is performed. The sensor sensitivity, inertia, and stability are analyzed. Findings – The micro-flow sensor exhibits good stability, suitable sensitivity, and inertia for integral measurements of water flow. Practical implications – Advantages of a micro-flow sensor using a TFST include low energy consumption, simple measuring procedure, and passive electronics. Originality/value – This paper describes initial work on a micro-flow se...
We have combined sol-gel synthetic route with hydrothermal synthesis under autogenous pressure to... more We have combined sol-gel synthetic route with hydrothermal synthesis under autogenous pressure to obtain stable TiO2 precursor gels. The gels were mixed with organic functional additives into pastes, and deposited onto fluorine-doped tin oxide (FTO) conductive substrates (12-14 Ω/sq) using tape-casting film applicator. As deposited films were carefully dried at 60-100°C, and calcined at 400°C, resulting in porous crack-free structures. The porous films were produced in different thicknesses (2-18 μm) and used as photoactive electrodes in dye-sensitized solar cells (DSSCs). Also, we have introduced a compact passivating TiO2 layer (100-300 nm in thickness), which prevents the direct contact between the conductive oxide substrate and electrolyte, thus, increasing the current density of the operating cell. The layer was produced by spin-coating deposition of TiO2 sols, prepared by chemical procedure starting from Ti(IV) isopropoxide and triethanolamine (TEA) as complexing agent. Therma...
Nb doped BaCe0.9Y0.1O2.95 (BCY) powders were synthesized by both solid state reaction (SSR) and a... more Nb doped BaCe0.9Y0.1O2.95 (BCY) powders were synthesized by both solid state reaction (SSR) and autocombustion reaction (ACR) method to investigate how different synthesis routes influence the properties of the powders and sintered samples. The powders were uniaxially pressed and sintered at 1550 degrees C to form dense electrolyte samples. Stability of BCY in CO2 can be increased by doping with Nb, but at the same time its electrical conductivities are reduced to a certain extent. It was shown that conductivities depended on both mechanism of defect formation, lattice parameters and microstructure of the electrolytes. Finer, less agglomerated powders were obtained by the method of autocombustion. SEM analysis revealed somewhat larger average grain size of the sintered samples synthesized by the ACR method. Total electrical conductivities were determined by electrochemical impedance spectroscopy (EIS) measurements in temperature range from 550 degrees C to 750 degrees C in a wet arg...
Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese and n... more Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese and nickel oxide was additionally mechanically activated in a high energy planetary ball mill for 5-60 min in order to obtain a pure NiMn(2)O(4) phase. The as-prepared powders were uniaxially pressed into disc shape pellets and then sintered for 60 min at 1200 degrees C. Changes in the particle morphology induced by mechanical activation were monitored using scanning electron microscopy, while changes in powder structural characteristics were followed using X-ray powder diffraction. The ac impedance spectroscopy was performed on sintered nickel manganite samples at 25 degrees C, 50 degrees C and 80 degrees C. It was shown that mechanical activation intensifies transport processes causing a decrease in the average crystallites size, while longer activation times can lead to the formation of aggregates, defects and increase of lattice microstrains. The observed changes in microstructures were c...
... S. Savić 1 , D. Luković 1 , S. Vujatović 1 , D. Vasiljević-Radović 2 , K. Radulović 2 and S. ... more ... S. Savić 1 , D. Luković 1 , S. Vujatović 1 , D. Vasiljević-Radović 2 , K. Radulović 2 and S. Djurić 1 1Institute of Technical Sciences of SASA, Belgrade, Serbia and Montenegro 2Institute of Microelectronics Technologies and Single Crystals, Belgrade, Serbia and Montenegro ...
2008 26th International Conference on Microelectronics, 2008
A novel uniaxial anemometer was created using a NTC thick film segmented thermistor to measure wi... more A novel uniaxial anemometer was created using a NTC thick film segmented thermistor to measure wind speed and direction. The anemometer operated on the principle of heat loss caused by the air volume flow and air speed. A NTC segmented thermistor served as a wind sensor in the anemometer. It was self-heated by a DC constant voltage. The self-heated DC
ABSTRACT An investigation path starting from (Mn,Ni,Co,Fe)3O4 nanometric powder preparation, NTC ... more ABSTRACT An investigation path starting from (Mn,Ni,Co,Fe)3O4 nanometric powder preparation, NTC thick-film characterization, realization and optimization of new planar thermistor geometries to custom design thermistors and their application for temperature and volume airflow sensors was recently determined. The aim was to make custom designed segmented NTC thermistors printed and sintered on alumina. Two types of volume airflow sensors were formed: indirectly heated and self-heated. A pair of segmented thermistors was placed in an air guide and connected to differential branches of the Wheatstone bridge. A heater was placed in the middle between the thermistors for the indirectly heated type, while for the self-heated type the same thermistors were self-heated by a constant current source. First the thermistor responses vs. the airflow (calibration curves) were measured, and then thermistor responses in time (inertia) to fast airflow changes from the minimum to the maximum. The results obtained could be applied in air conditioning for air guide flow regulation.
... MV Nikolic,1 N. Obradovic,2,5 KM Paraskevopoulos,3 TT Zorba,3 SM Savic,2 and MM Ristic4 UDC 6... more ... MV Nikolic,1 N. Obradovic,2,5 KM Paraskevopoulos,3 TT Zorba,3 SM Savic,2 and MM Ristic4 UDC 621.762 ... In this paper, changes in the structure of Zn2TiO4 due to doping with small amounts of MgO have been studied by x-ray diffraction and infrared reflection spectroscopy. ...
... PM Nikoli 1 ,* , S. Ðuri 1 , KM Paraskevopoulos 2 , TT Zorba 2 , D. Lukovi 1 , S. Savi 1 , V.... more ... PM Nikoli 1 ,* , S. Ðuri 1 , KM Paraskevopoulos 2 , TT Zorba 2 , D. Lukovi 1 , S. Savi 1 , V. Blagojevi 3 and MV Nikoli 4 ... We would like to acknowledge D. Stojanovi , who provided the crystals for far-IR measurements, Dr Chris Hayward, Associate Editor, Prof. ...
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