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Tadashi Shiosaki - One of the best experts on this subject based on the ideXlab platform.

  • fabrication and Positive Temperature Coefficient of resistivity properties of semiconducting ceramics based on the batio3 bi1 2k1 2 tio3 system
    2010
    Co-Authors: Hiroaki Takeda, Hisashi Harinaka, Tadashi Shiosaki, M A Zubair, C Leach, Robert Freer, Takuya Hoshina, Takaaki Tsurumi
    Abstract:

    Abstract BaTiO 3 –(Bi 1/2 K 1/2 )TiO 3 (BT–BKT) ceramics have a low ρ RT of 10 1 –10 2  Ω cm like that of semiconducting materials prepared by sintering in a N 2 flow with low O 2 concentration. By annealing in air, the BT–BKT ceramics show an abrupt increase in their resistivity near the T c , namely, a Positive Temperature Coefficient of resistivity (PTC) characteristic. With 5 mol% and 10 mol% BKT added to BT, the ceramics display the PTC characteristic at 155 °C and 165 °C, respectively. Furthermore, the ratio, ρ max / ρ RT , of the highest resistivity ( ρ max ) and the resistivity at room Temperature ( ρ RT ) of the ceramics increased on adding a small amount of Mn and a sintering aid.

  • annealing effects on the characteristics of high tc lead free barium titanate based Positive Temperature Coefficient of resistivity ceramics
    2008
    Co-Authors: Pinghua Xiang, Hisashi Harinaka, Hiroaki Takeda, Takashi Nishida, Kiyoshi Uchiyama, Tadashi Shiosaki
    Abstract:

    Annealing effects on the Positive Temperature Coefficient of resistivity (PTCR) behavior of (Bi1/2Na1/2)TiO3 and (Bi1/2K1/2)TiO3 modified BaTiO3 semiconducting ceramics are investigated. The annealing treatments result in the occurrence of the PTCR effect and the increased resistivity jump. The impedance spectra reveal that the resistivity of grain interior of annealed sample is little influenced by the annealing process, indicating that the increase in the overall resistivity is entirely a grain-boundary effect. A higher annealing Temperature leads to an increase in acceptor state density, potential barrier height and barrier layer width, which contributes to the improved PTCR effect in the annealed samples.

  • characterization of manganese doped batio3 bi1 2na1 2 tio3 Positive Temperature Coefficient of resistivity ceramics using impedance spectroscopy
    2008
    Co-Authors: Pinghua Xiang, Hiroaki Takeda, Tadashi Shiosaki
    Abstract:

    Small amount of manganese (Mn)-doped BaTiO3–(Bi1∕2Na1∕2)TiO3 (BT-BNT) Positive Temperature Coefficient of resistivity ceramics are investigated by impedance analyses. The impedance/modulus spectroscopic plots reveal that a third resistance-capacitance (RC) response besides grains and grain boundaries is exhibited in the Mn-free BT-BNT ceramic with 4mol% BNT, but is not observed in the Mn-doped samples. The third RC element can be attributed to a barium vacancy-rich layer in the outer grain region. The evidence of impedance spectroscopy indicates that the highly Bi donor is partially compensated by the Mn acceptor and the predominant charge compensation defect shifts from barium vacancies to electrons with doping small amount of Mn dopant.

  • Positive Temperature Coefficient of resistivity effect of semiconducting batio3 bi1 2na1 2 tio3 ceramics prepared by a wet chemistry route
    2007
    Co-Authors: Pinghua Xiang, Hiroaki Takeda, Tadashi Shiosaki
    Abstract:

    Without any additional donor dopants, BaTiO3–(Bi1/2Na1/2)TiO3 (BT–BNT) Positive Temperature Coefficient of resistivity (PTCR) ceramics were successfully prepared by a wet-chemistry route. With 2 mol % BNT addition, the obtained BT–BNT ceramics had semiconductivity and exhibited a PTCR behavior at about 155 °C. The onset Temperature of the PTCR effect increased to ~165 °C for the 4 mol % BNT added samples. Room-Temperature resistivity ρRT increased with the content of BNT added and the ceramics changed from a semiconductor to an insulator, which was consistent with the variation of the microstructure. The Temperature of resistivity anomaly in BT–BNT ceramics also increased with increasing BNT content. A small amount of manganese (Mn) dopant was found to improve the PTCR effect in the BT–BNT system. The possible mechanism underlying the PTCR effect in BT–BNT ceramics was proposed.

  • high tc lead free batio3 bi1 2na1 2 tio3 Positive Temperature Coefficient of resistivity ceramics with electrically heterogeneous structure
    2007
    Co-Authors: Pinghua Xiang, Hiroaki Takeda, Tadashi Shiosaki
    Abstract:

    A distinct Positive Temperature Coefficient of resistivity effect has been observed in BaTiO3–(Bi1∕2Na1∕2)TiO3 (BT-BNT) ceramics sintered in a N2 flow with low O2 concentration. With the addition of BNT, the samples exhibit resistivity jumps of ∼103–105 starting at ∼190–210°C. X-ray diffraction results indicate that the BNT phase and BT phase formed a solid solution during sintering. An electrically heterogeneous structure, consisting of the grain interiors, outer grain shells, and grain boundaries, is revealed by the complex impedance analyses. The observed dc resistivity jump is attributed to the rapid resistivity rise in both grain boundaries and grain shells.

Hiroaki Takeda - One of the best experts on this subject based on the ideXlab platform.

  • bulk response and grain boundary microelectrical activity of high t c batio 3 bi 1 2 k 1 2 tio 3 based Positive Temperature Coefficient of resistance ceramics
    2013
    Co-Authors: Hiroaki Takeda, C Leach, Robert Freer, Takuya Hoshina, Mohammad A Zubair, Takaaki Tsurumi
    Abstract:

    Lead-free Positive Temperature Coefficient of resistance (PTC) thermistors were synthesized from (1 − x/100)BaTiO3–(x/100)(Bi1/2K1/2)TiO3-based solid solutions, using a conventional mixed-oxide fabrication route, and sintered in N2 followed by air annealing. A maximum TC of 205 °C was achieved for x = 20. An increase in x from 0 to 20 decreased the grain size by more than 92% and increased room Temperature resistivity (ρRT) by 7 orders of magnitude. For x ≤ 10, PTC ratio (ρmax/ρmin) ≈ 104.5 and Temperature Coefficient of resistivity (α) > 10.3%/°C were achieved using Mn and Al2O3:SiO2:TiO2 (AST) additions. For x > 10, ρmax/ρmin > 103 and α > 8%/°C were only obtained in samples sintered in N2 without subsequent air annealing. Complex impedance analysis revealed three relaxation processes, attributed to a semiconducting grain core, a PTC active grain boundary interface, and a grain boundary insulating layer. Local electrical activity was investigated by hot-stage conductive mode microscopy. The existence of symmetrical grain boundary electron beam-induced current and β-conductivity contrast at the grain boundaries, consistent with the presence of an electron trapping two-dimensional grain boundary plane, compensated by Positive space charge layers and a low conductivity vacancy-rich layer, was revealed for the first time within this system.

  • fabrication and Positive Temperature Coefficient of resistivity properties of semiconducting ceramics based on the batio3 bi1 2k1 2 tio3 system
    2010
    Co-Authors: Hiroaki Takeda, Hisashi Harinaka, Tadashi Shiosaki, M A Zubair, C Leach, Robert Freer, Takuya Hoshina, Takaaki Tsurumi
    Abstract:

    Abstract BaTiO 3 –(Bi 1/2 K 1/2 )TiO 3 (BT–BKT) ceramics have a low ρ RT of 10 1 –10 2  Ω cm like that of semiconducting materials prepared by sintering in a N 2 flow with low O 2 concentration. By annealing in air, the BT–BKT ceramics show an abrupt increase in their resistivity near the T c , namely, a Positive Temperature Coefficient of resistivity (PTC) characteristic. With 5 mol% and 10 mol% BKT added to BT, the ceramics display the PTC characteristic at 155 °C and 165 °C, respectively. Furthermore, the ratio, ρ max / ρ RT , of the highest resistivity ( ρ max ) and the resistivity at room Temperature ( ρ RT ) of the ceramics increased on adding a small amount of Mn and a sintering aid.

  • annealing effects on the characteristics of high tc lead free barium titanate based Positive Temperature Coefficient of resistivity ceramics
    2008
    Co-Authors: Pinghua Xiang, Hisashi Harinaka, Hiroaki Takeda, Takashi Nishida, Kiyoshi Uchiyama, Tadashi Shiosaki
    Abstract:

    Annealing effects on the Positive Temperature Coefficient of resistivity (PTCR) behavior of (Bi1/2Na1/2)TiO3 and (Bi1/2K1/2)TiO3 modified BaTiO3 semiconducting ceramics are investigated. The annealing treatments result in the occurrence of the PTCR effect and the increased resistivity jump. The impedance spectra reveal that the resistivity of grain interior of annealed sample is little influenced by the annealing process, indicating that the increase in the overall resistivity is entirely a grain-boundary effect. A higher annealing Temperature leads to an increase in acceptor state density, potential barrier height and barrier layer width, which contributes to the improved PTCR effect in the annealed samples.

  • characterization of manganese doped batio3 bi1 2na1 2 tio3 Positive Temperature Coefficient of resistivity ceramics using impedance spectroscopy
    2008
    Co-Authors: Pinghua Xiang, Hiroaki Takeda, Tadashi Shiosaki
    Abstract:

    Small amount of manganese (Mn)-doped BaTiO3–(Bi1∕2Na1∕2)TiO3 (BT-BNT) Positive Temperature Coefficient of resistivity ceramics are investigated by impedance analyses. The impedance/modulus spectroscopic plots reveal that a third resistance-capacitance (RC) response besides grains and grain boundaries is exhibited in the Mn-free BT-BNT ceramic with 4mol% BNT, but is not observed in the Mn-doped samples. The third RC element can be attributed to a barium vacancy-rich layer in the outer grain region. The evidence of impedance spectroscopy indicates that the highly Bi donor is partially compensated by the Mn acceptor and the predominant charge compensation defect shifts from barium vacancies to electrons with doping small amount of Mn dopant.

  • Positive Temperature Coefficient of resistivity effect of semiconducting batio3 bi1 2na1 2 tio3 ceramics prepared by a wet chemistry route
    2007
    Co-Authors: Pinghua Xiang, Hiroaki Takeda, Tadashi Shiosaki
    Abstract:

    Without any additional donor dopants, BaTiO3–(Bi1/2Na1/2)TiO3 (BT–BNT) Positive Temperature Coefficient of resistivity (PTCR) ceramics were successfully prepared by a wet-chemistry route. With 2 mol % BNT addition, the obtained BT–BNT ceramics had semiconductivity and exhibited a PTCR behavior at about 155 °C. The onset Temperature of the PTCR effect increased to ~165 °C for the 4 mol % BNT added samples. Room-Temperature resistivity ρRT increased with the content of BNT added and the ceramics changed from a semiconductor to an insulator, which was consistent with the variation of the microstructure. The Temperature of resistivity anomaly in BT–BNT ceramics also increased with increasing BNT content. A small amount of manganese (Mn) dopant was found to improve the PTCR effect in the BT–BNT system. The possible mechanism underlying the PTCR effect in BT–BNT ceramics was proposed.

Pinghua Xiang - One of the best experts on this subject based on the ideXlab platform.

  • annealing effects on the characteristics of high tc lead free barium titanate based Positive Temperature Coefficient of resistivity ceramics
    2008
    Co-Authors: Pinghua Xiang, Hisashi Harinaka, Hiroaki Takeda, Takashi Nishida, Kiyoshi Uchiyama, Tadashi Shiosaki
    Abstract:

    Annealing effects on the Positive Temperature Coefficient of resistivity (PTCR) behavior of (Bi1/2Na1/2)TiO3 and (Bi1/2K1/2)TiO3 modified BaTiO3 semiconducting ceramics are investigated. The annealing treatments result in the occurrence of the PTCR effect and the increased resistivity jump. The impedance spectra reveal that the resistivity of grain interior of annealed sample is little influenced by the annealing process, indicating that the increase in the overall resistivity is entirely a grain-boundary effect. A higher annealing Temperature leads to an increase in acceptor state density, potential barrier height and barrier layer width, which contributes to the improved PTCR effect in the annealed samples.

  • characterization of manganese doped batio3 bi1 2na1 2 tio3 Positive Temperature Coefficient of resistivity ceramics using impedance spectroscopy
    2008
    Co-Authors: Pinghua Xiang, Hiroaki Takeda, Tadashi Shiosaki
    Abstract:

    Small amount of manganese (Mn)-doped BaTiO3–(Bi1∕2Na1∕2)TiO3 (BT-BNT) Positive Temperature Coefficient of resistivity ceramics are investigated by impedance analyses. The impedance/modulus spectroscopic plots reveal that a third resistance-capacitance (RC) response besides grains and grain boundaries is exhibited in the Mn-free BT-BNT ceramic with 4mol% BNT, but is not observed in the Mn-doped samples. The third RC element can be attributed to a barium vacancy-rich layer in the outer grain region. The evidence of impedance spectroscopy indicates that the highly Bi donor is partially compensated by the Mn acceptor and the predominant charge compensation defect shifts from barium vacancies to electrons with doping small amount of Mn dopant.

  • Positive Temperature Coefficient of resistivity effect of semiconducting batio3 bi1 2na1 2 tio3 ceramics prepared by a wet chemistry route
    2007
    Co-Authors: Pinghua Xiang, Hiroaki Takeda, Tadashi Shiosaki
    Abstract:

    Without any additional donor dopants, BaTiO3–(Bi1/2Na1/2)TiO3 (BT–BNT) Positive Temperature Coefficient of resistivity (PTCR) ceramics were successfully prepared by a wet-chemistry route. With 2 mol % BNT addition, the obtained BT–BNT ceramics had semiconductivity and exhibited a PTCR behavior at about 155 °C. The onset Temperature of the PTCR effect increased to ~165 °C for the 4 mol % BNT added samples. Room-Temperature resistivity ρRT increased with the content of BNT added and the ceramics changed from a semiconductor to an insulator, which was consistent with the variation of the microstructure. The Temperature of resistivity anomaly in BT–BNT ceramics also increased with increasing BNT content. A small amount of manganese (Mn) dopant was found to improve the PTCR effect in the BT–BNT system. The possible mechanism underlying the PTCR effect in BT–BNT ceramics was proposed.

  • high tc lead free batio3 bi1 2na1 2 tio3 Positive Temperature Coefficient of resistivity ceramics with electrically heterogeneous structure
    2007
    Co-Authors: Pinghua Xiang, Hiroaki Takeda, Tadashi Shiosaki
    Abstract:

    A distinct Positive Temperature Coefficient of resistivity effect has been observed in BaTiO3–(Bi1∕2Na1∕2)TiO3 (BT-BNT) ceramics sintered in a N2 flow with low O2 concentration. With the addition of BNT, the samples exhibit resistivity jumps of ∼103–105 starting at ∼190–210°C. X-ray diffraction results indicate that the BNT phase and BT phase formed a solid solution during sintering. An electrically heterogeneous structure, consisting of the grain interiors, outer grain shells, and grain boundaries, is revealed by the complex impedance analyses. The observed dc resistivity jump is attributed to the rapid resistivity rise in both grain boundaries and grain shells.

Joong Hee Lee - One of the best experts on this subject based on the ideXlab platform.

  • synergy effect of hybrid fillers on the Positive Temperature Coefficient behavior of polypropylene ultra high molecular weight polyethylene composites
    2010
    Co-Authors: Siddaramaiah Basavarajaiah, Nam Hoon Kim, Seokbong Heo, Joong Hee Lee
    Abstract:

    Hybrid nanocomposites of polypropylene/ultra-high molecular weight polyethylene (PP/UHMWPE, 70/30) with various amounts of carbon black (CB) and carboxylated multiwalled carbon nanotubes (c-MWNTs) were prepared by the solution mixing and melt blending techniques. The effects of the mixture of CB and c-MWNTs on the Positive-Temperature-Coefficient (PTC) behavior and the negative-Temperature-Coefficient (NTC) behavior, as well as the room Temperature resistivity, were studied. The transmission electron microscopy (TEM) images showed that the CB particles were aggregated at the interface, between PP and UHMWPE. This selective localization of the CB particles at the interface along with the formation of continuous conducting media leads to the formation of additional conducting networks, resulting in a percolation threshold at a low CB content. A synergy effect of the hybrid conducting fillers of CB and c-MWNTs on the PTC behavior of the hybrid blends was also observed. The room Temperature resistivity was reduced significantly by the incorporation of the c-MWNTs into the PP/UHMWPE/CB composite. The intensity and repeatability of the PTC effect in the nanocomposites were improved and the NTC effect weakened by incorporating a small amount (0.5 wt %) of c-MWNTs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

  • Positive Temperature Coefficient characteristic and structure of graphite nanofibers reinforced high density polyethylene carbon black nanocomposites
    2009
    Co-Authors: Nam Hoon Kim, Gyehyoung Yoo, Joong Hee Lee
    Abstract:

    Abstract Graphite nanofibers (GNF) and carbon black (CB) filled high density polyethylene (HDPE) hybrid composites were fabricated using a melt mixing method. The effects of the CB and GNF content on the room Temperature resistivity and Positive Temperature Coefficient (PTC) behavior of the nanocomposites were examined. The room Temperature resistivity of the composites decreased significantly with increasing GNF content, but this was not always the case with the PTC intensity. The incorporation of a small amount of GNF into the HDPE/CB composites significantly improved the PTC intensity and reproducibility of the hybrid nanocomposites. The maximum PTC effect, whose log intensity was approximately 7.2, was observed in the HDPE/CB/GNF (80/20/0.25 wt%) nanocomposite with relatively low room Temperature resistivity. The mechanism for the effects of GNF in HDPE/CB/GNF hybrid composites were examined using differential scanning calorimetry, transmission scanning electron microscopy and X-ray diffraction.

  • Positive Temperature Coefficient behavior of the graphite nanofibre and carbon black filled high density polyethylene hybrid composites
    2008
    Co-Authors: Jong Wan Kim, Tae Hee Shim, Yun Ki Jang, Joong Hee Lee
    Abstract:

    The graphite nanofiber (GNF) and carbon black filled high-density polyethylene (HDPE) hybrid nanocomposites were prepared by solution mixing and melt blending techniques. The effect of addition of GNF on the Positive Temperature Coefficient (PTC) behavior of the nanocomposites was investigated. The incorporation of small amount of GNF into HDPE/CB composites showed a significant improvement in PTC intensity and repeatability of the hybrid nanocomposites. The maximum PTC intensity was observed for the HDPE/CB/GNF (80/20/0.25) nanocomposite with a relatively low room Temperature resistivity.

  • effects of the addition of multi walled carbon nanotubes on the Positive Temperature Coefficient characteristics of carbon black filled high density polyethylene nanocomposites
    2006
    Co-Authors: Joong Hee Lee, Sung Kwan Kim, Nam Hoon Kim
    Abstract:

    This study investigates the effects of the addition of multi-walled carbon nanotubes (MWNTs) on the Positive Temperature Coefficient (PTC) characteristics of conventional carbon black (CB)/high-density polyethylene (HDPE) composites. MWNT/CB/HDPE hybrid nanocomposites were prepared by the combined solution and melt-mixing process. The obtained results indicated that the PTC intensity and repeatability of the hybrid nanocomposites were dramatically improved by adding a small amount of MWNT and that the optimal MWNT content corresponded to the CB content. The initial resistivity of the materials decreased with increasing MWNT content, but not always in the PTC intensity.

Takaaki Tsurumi - One of the best experts on this subject based on the ideXlab platform.

  • bulk response and grain boundary microelectrical activity of high t c batio 3 bi 1 2 k 1 2 tio 3 based Positive Temperature Coefficient of resistance ceramics
    2013
    Co-Authors: Hiroaki Takeda, C Leach, Robert Freer, Takuya Hoshina, Mohammad A Zubair, Takaaki Tsurumi
    Abstract:

    Lead-free Positive Temperature Coefficient of resistance (PTC) thermistors were synthesized from (1 − x/100)BaTiO3–(x/100)(Bi1/2K1/2)TiO3-based solid solutions, using a conventional mixed-oxide fabrication route, and sintered in N2 followed by air annealing. A maximum TC of 205 °C was achieved for x = 20. An increase in x from 0 to 20 decreased the grain size by more than 92% and increased room Temperature resistivity (ρRT) by 7 orders of magnitude. For x ≤ 10, PTC ratio (ρmax/ρmin) ≈ 104.5 and Temperature Coefficient of resistivity (α) > 10.3%/°C were achieved using Mn and Al2O3:SiO2:TiO2 (AST) additions. For x > 10, ρmax/ρmin > 103 and α > 8%/°C were only obtained in samples sintered in N2 without subsequent air annealing. Complex impedance analysis revealed three relaxation processes, attributed to a semiconducting grain core, a PTC active grain boundary interface, and a grain boundary insulating layer. Local electrical activity was investigated by hot-stage conductive mode microscopy. The existence of symmetrical grain boundary electron beam-induced current and β-conductivity contrast at the grain boundaries, consistent with the presence of an electron trapping two-dimensional grain boundary plane, compensated by Positive space charge layers and a low conductivity vacancy-rich layer, was revealed for the first time within this system.

  • fabrication and Positive Temperature Coefficient of resistivity properties of semiconducting ceramics based on the batio3 bi1 2k1 2 tio3 system
    2010
    Co-Authors: Hiroaki Takeda, Hisashi Harinaka, Tadashi Shiosaki, M A Zubair, C Leach, Robert Freer, Takuya Hoshina, Takaaki Tsurumi
    Abstract:

    Abstract BaTiO 3 –(Bi 1/2 K 1/2 )TiO 3 (BT–BKT) ceramics have a low ρ RT of 10 1 –10 2  Ω cm like that of semiconducting materials prepared by sintering in a N 2 flow with low O 2 concentration. By annealing in air, the BT–BKT ceramics show an abrupt increase in their resistivity near the T c , namely, a Positive Temperature Coefficient of resistivity (PTC) characteristic. With 5 mol% and 10 mol% BKT added to BT, the ceramics display the PTC characteristic at 155 °C and 165 °C, respectively. Furthermore, the ratio, ρ max / ρ RT , of the highest resistivity ( ρ max ) and the resistivity at room Temperature ( ρ RT ) of the ceramics increased on adding a small amount of Mn and a sintering aid.