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Hirotaka Ogawa - One of the best experts on this subject based on the ideXlab platform.

  • influence of sintering temperature on Microwave Dielectric Property and crystal structure of corundum structured mg4nbsbo9 ceramic
    Journal of Alloys and Compounds, 2009
    Co-Authors: Akinori Kan, Hirotaka Ogawa
    Abstract:

    Abstract The relationships between the influence of the sintering temperature on the Microwave Dielectric properties and crystal structure of Mg 4 NbSbO 9 (MNS) ceramics with corundum structure were investigated in this study. From the XRPD patterns, it was found that the MgO compound was identified as a secondary phase in the XRPD patterns of MNS ceramic when the samples were sintered at the sintering temperatures higher than 1500 °C because of the vaporization of Sb in MNS ceramic. The Dielectric constants of MNS ceramic increased from 10 to 13 in the temperature range of 1375–1500 °C, whereas those of MNS ceramic decreased at the sintering temperatures above 1550 °C. The quality factors ( Q · f ) of MNS ceramic also decreased from 275,000 to 5000 GHz at the sintering temperatures above 1550 °C. Such a decrease in Q · f values may be related to the vaporization of Sb and the formation of a secondary phase. The temperature coefficient of resonant frequency was ranged from −56 to −46 ppm/°C.

  • synthesis and crystal structure Microwave Dielectric Property relations in sn substituted ca3 zr1 xsnx si2o9 solid solutions with cuspidine structure
    Japanese Journal of Applied Physics, 2007
    Co-Authors: Akinori Kan, Hirotaka Ogawa, Hitoshi Ohsato
    Abstract:

    The effects of Sn substitution for Zr on the Microwave Dielectric properties and crystal structure of Ca3(Zr1-xSnx)Si2O9 (CZSS) solid solutions were investigated in this study. The X-ray powder diffraction (XRPD) patterns of CZSS solid solutions were indicated to be a single phase, which corresponded to the cuspidine-type structure. The lattice parameters of CZSS solid solutions linearly decreased with increasing composition x, following Vegard's law. The Dielectric constant (er) of CZSS solid solutions slightly decreased from 10.6 to 8.4, whereas the quality factor (Qf) of the solid solutions increased from 54791 to 93296 GHz, depending on the composition x. As a result, the highest Qf value of 93296 GHz was obtained at x=1 where the Dielectric constant and temperature coefficient of resonant frequency were 8.4 and -64.7 ppm/°C, respectively. The decreases in the Dielectric constant and the increase in Qf values primarily depend on the composition x. This may be caused by the increase in the covalency of the (Zr,Sn)–O bond in the octahedron.

  • relationship between crystal structure and Microwave Dielectric properties of melilite type ceramic
    Journal of The European Ceramic Society, 2007
    Co-Authors: Atsushi Yokoi, Akinori Kan, Hirotaka Ogawa, Yoshifumi Nakamura
    Abstract:

    Abstract Crystal structure–Microwave Dielectric Property relations in the melilite-type Ba 2 (Mg 1− x Zn x )Si 2 O 7 ceramics were investigated in this study. The formation of a secondary phase was not detected over the whole composition range. Also, the lattice parameter, a , of the solid solutions decreased linearly with increasing the composition x , while the lattice parameter, c , was increased by the Zn substitution for Mg. Also, the covalency of the Mg O bond increased from 26 to 35% in the composition range of 0–0.75. Moreover, the covalency of the Zn O bond increased in the composition range of 0.25–1, while that of Si O bonds in the SiO 4 tetrahedron remained approximately constant over the whole composition range. The Dielectric constants ( ɛ r ) of the solid solutions were on the order of approximately 7.5, and the quality factors ( Q · f ) of the solid solutions increased with increasing the composition x . The temperature coefficient of resonant frequency ( τ f ) of the solid solutions varied from −62 to −74 ppm/°C with increasing the composition x ; therefore, the Zn substitution for Mg was not effective in improving the τ f value in this system.

  • low temperature sintering Microwave Dielectric Property relations in ba3 vo4 2 ceramic
    Journal of Alloys and Compounds, 2006
    Co-Authors: Ryosuke Umemura, Hirotaka Ogawa, Atsushi Yokoi, Hitoshi Ohsato
    Abstract:

    Abstract The Ba 3 (VO 4 ) 2 – x  wt.%B 2 O 3 ( x  = 0–5) ceramics were prepared by the solid state reaction method in order to reduce the sintering temperature. The saturated bulk densities of Ba 3 (VO 4 ) 2 – x  wt.%B 2 O 3 ceramics were shifted toward lower sintering temperatures with increased the amounts of B 2 O 3 doping, and then an improvement in the quality factor ( Q · f ) of the samples was recognized at the lower sintering temperatures. As a result, the Q · f value of 41,065 GH, the ɛ r of 12.5 and the τ f value of 38.8 ppm/°C were obtained in the sample of the Ba 3 (VO 4 ) 2 –0.5 wt.%B 2 O 3 ceramic sintered at the temperature of 950 °C. However, the Q · f values of the sample with B 2 O 3 higher than that of 3 wt.% additions decreased because of the formation of secondary phase and abnormal grain growth of the sample. As for the chemical compatibility with silver, no secondary phase was detected in the XRPD pattern when the mixtures of Ba 3 (VO 4 ) 2 –1 wt.%B 2 O 3 ceramics and Ag powders were heat-treated at 900 °C for 1 h in air.

  • crystal structure Microwave Dielectric Property relations in sm nb1 xtax ti1 yzry o6 ceramics
    Journal of The European Ceramic Society, 2006
    Co-Authors: Takeshi Oishi, Hitoshi Ohsato, Akinori Kan, Hirotaka Ogawa
    Abstract:

    Abstract The effects of the Ta substitution for Nb and the Zr substitution for Ti on the Microwave Dielectric properties and crystal structure of Sm(Nb 1− x Ta x )(Ti 1− y Zr y )O 6 ceramics were investigated in this study. The Sm(Nb 1− x Ta x )TiO 6 ( x  = 0–1) ceramics were single phase, whereas the limit of solid solutions for the SmTa(Ti 1− y Zr y )O 6 ceramics was y  = 0.4. In the case of the Sm(Nb 1− x Ta x )TiO 6 ceramics, the Dielectric constant and the temperature coefficient of resonant frequency were decreased, whereas the quality factor was increased by the Ta substitution for Nb. The maximum Q  ·  f value was obtained when the SmTaTiO 6 was synthesized, and the Microwave Dielectric properties are, ɛ r  = 37.6; τ f  = 24.2 ppm/°C; and Q  ·  f  = 24541 GHz. On the other hand, the Dielectric constants of the SmTa(Ti 1− y Zr y )O 6 ceramics were decreased from 37.6 to 28.9, whereas the quality factor was increased from 24541 to 38320 GHz with increasing composition y from 0 to 0.4. The temperature coefficient of resonant frequency of the ceramics varied from 24.2 to −11.6 ppm/°C. A near zero temperature coefficient of resonant frequency results from the composition of y  = 0.3 with a Dielectric constant of 31.1 and Q  ·  f value of 37481 GHz.

Hitoshi Ohsato - One of the best experts on this subject based on the ideXlab platform.

  • synthesis and crystal structure Microwave Dielectric Property relations in sn substituted ca3 zr1 xsnx si2o9 solid solutions with cuspidine structure
    Japanese Journal of Applied Physics, 2007
    Co-Authors: Akinori Kan, Hirotaka Ogawa, Hitoshi Ohsato
    Abstract:

    The effects of Sn substitution for Zr on the Microwave Dielectric properties and crystal structure of Ca3(Zr1-xSnx)Si2O9 (CZSS) solid solutions were investigated in this study. The X-ray powder diffraction (XRPD) patterns of CZSS solid solutions were indicated to be a single phase, which corresponded to the cuspidine-type structure. The lattice parameters of CZSS solid solutions linearly decreased with increasing composition x, following Vegard's law. The Dielectric constant (er) of CZSS solid solutions slightly decreased from 10.6 to 8.4, whereas the quality factor (Qf) of the solid solutions increased from 54791 to 93296 GHz, depending on the composition x. As a result, the highest Qf value of 93296 GHz was obtained at x=1 where the Dielectric constant and temperature coefficient of resonant frequency were 8.4 and -64.7 ppm/°C, respectively. The decreases in the Dielectric constant and the increase in Qf values primarily depend on the composition x. This may be caused by the increase in the covalency of the (Zr,Sn)–O bond in the octahedron.

  • raman spectroscopic evaluation and Microwave Dielectric Property of order disorder and stoichiometric non stoichiometric ba zn1 3ta2 3 o3
    Ferroelectrics, 2007
    Co-Authors: Eiichi Koga, Kenichi Kakimoto, Hiroki Moriwake, Hitoshi Ohsato
    Abstract:

    The phonon vibrations, crystal phases, lattice defects and Q factors of stoichiometric Ba(Zn1/3Ta2/3)O3 (BZT) and non-stoichiometric BZT were studied. The significant Q factor decrement and the change of the phonon vibration were simultaneously observed in the non-stoichiometric disordered BZT formed in Ba-rich region. The Q factor decrement in the non-stoichiometric disordered BZT can be attributed to the change of A 1g (O) mode. These results suggest that the lattice defects (B site vacancy and oxygen vacancy) formed by excessive Ba should play an important role in the phonon vibration and Q factor of BZT. On the contrary, in the case of the stoichiometric BZT, the ionic vibrations detected by Raman scattering were independent of the crystal-structural ordering and Microwave Q factor.

  • low temperature sintering Microwave Dielectric Property relations in ba3 vo4 2 ceramic
    Journal of Alloys and Compounds, 2006
    Co-Authors: Ryosuke Umemura, Hirotaka Ogawa, Atsushi Yokoi, Hitoshi Ohsato
    Abstract:

    Abstract The Ba 3 (VO 4 ) 2 – x  wt.%B 2 O 3 ( x  = 0–5) ceramics were prepared by the solid state reaction method in order to reduce the sintering temperature. The saturated bulk densities of Ba 3 (VO 4 ) 2 – x  wt.%B 2 O 3 ceramics were shifted toward lower sintering temperatures with increased the amounts of B 2 O 3 doping, and then an improvement in the quality factor ( Q · f ) of the samples was recognized at the lower sintering temperatures. As a result, the Q · f value of 41,065 GH, the ɛ r of 12.5 and the τ f value of 38.8 ppm/°C were obtained in the sample of the Ba 3 (VO 4 ) 2 –0.5 wt.%B 2 O 3 ceramic sintered at the temperature of 950 °C. However, the Q · f values of the sample with B 2 O 3 higher than that of 3 wt.% additions decreased because of the formation of secondary phase and abnormal grain growth of the sample. As for the chemical compatibility with silver, no secondary phase was detected in the XRPD pattern when the mixtures of Ba 3 (VO 4 ) 2 –1 wt.%B 2 O 3 ceramics and Ag powders were heat-treated at 900 °C for 1 h in air.

  • crystal structure Microwave Dielectric Property relations in sm nb1 xtax ti1 yzry o6 ceramics
    Journal of The European Ceramic Society, 2006
    Co-Authors: Takeshi Oishi, Hitoshi Ohsato, Akinori Kan, Hirotaka Ogawa
    Abstract:

    Abstract The effects of the Ta substitution for Nb and the Zr substitution for Ti on the Microwave Dielectric properties and crystal structure of Sm(Nb 1− x Ta x )(Ti 1− y Zr y )O 6 ceramics were investigated in this study. The Sm(Nb 1− x Ta x )TiO 6 ( x  = 0–1) ceramics were single phase, whereas the limit of solid solutions for the SmTa(Ti 1− y Zr y )O 6 ceramics was y  = 0.4. In the case of the Sm(Nb 1− x Ta x )TiO 6 ceramics, the Dielectric constant and the temperature coefficient of resonant frequency were decreased, whereas the quality factor was increased by the Ta substitution for Nb. The maximum Q  ·  f value was obtained when the SmTaTiO 6 was synthesized, and the Microwave Dielectric properties are, ɛ r  = 37.6; τ f  = 24.2 ppm/°C; and Q  ·  f  = 24541 GHz. On the other hand, the Dielectric constants of the SmTa(Ti 1− y Zr y )O 6 ceramics were decreased from 37.6 to 28.9, whereas the quality factor was increased from 24541 to 38320 GHz with increasing composition y from 0 to 0.4. The temperature coefficient of resonant frequency of the ceramics varied from 24.2 to −11.6 ppm/°C. A near zero temperature coefficient of resonant frequency results from the composition of y  = 0.3 with a Dielectric constant of 31.1 and Q  ·  f value of 37481 GHz.

  • Microwave Dielectric Property microstructure relationships in y2ba cu1 xmg x o5 solid solutions
    Journal of The European Ceramic Society, 2004
    Co-Authors: Katsuhiro Mori, Hirotaka Ogawa, Akinori Kan, Hitoshi Ohsato
    Abstract:

    Abstract Y 2 Ba(Cu 1− x Mg x )O 5 solid solutions were synthesized by the solid state reaction method and the microstructure was studied by using SEM in order to clarify the Microwave Dielectric Property–structure relationship. From the variations in the lattice parameters obtained by Rietveld analysis and the least-squares method, it was clarified that the limit of Y 2 Ba(Cu 1− x Mg x )O 5 solid solutions is approximately at x =0.2. Grain growth and the reduction of porosity in the samples increased with the composition x . The Dielectric constants were constant and the quality factors were extremely increased from 3800 to 42 300 GHz, as the composition x increased from 0 to 0.2. Thus, it was found that the quality factors of the samples were closely related to the morphological changes and a formation of the porosity; the temperature coefficient of resonant frequency of the samples ranged from −35.0 to −56.5 ppm/°C. Moreover, compared to Y 2 Ba(Cu 1− x Mg x )O 5 compound without cold isotropic pressure (CIP), that with CIP especially exhibited approximately 16% higher Q · f value.

Akinori Kan - One of the best experts on this subject based on the ideXlab platform.

  • influence of sintering temperature on Microwave Dielectric Property and crystal structure of corundum structured mg4nbsbo9 ceramic
    Journal of Alloys and Compounds, 2009
    Co-Authors: Akinori Kan, Hirotaka Ogawa
    Abstract:

    Abstract The relationships between the influence of the sintering temperature on the Microwave Dielectric properties and crystal structure of Mg 4 NbSbO 9 (MNS) ceramics with corundum structure were investigated in this study. From the XRPD patterns, it was found that the MgO compound was identified as a secondary phase in the XRPD patterns of MNS ceramic when the samples were sintered at the sintering temperatures higher than 1500 °C because of the vaporization of Sb in MNS ceramic. The Dielectric constants of MNS ceramic increased from 10 to 13 in the temperature range of 1375–1500 °C, whereas those of MNS ceramic decreased at the sintering temperatures above 1550 °C. The quality factors ( Q · f ) of MNS ceramic also decreased from 275,000 to 5000 GHz at the sintering temperatures above 1550 °C. Such a decrease in Q · f values may be related to the vaporization of Sb and the formation of a secondary phase. The temperature coefficient of resonant frequency was ranged from −56 to −46 ppm/°C.

  • synthesis and crystal structure Microwave Dielectric Property relations in sn substituted ca3 zr1 xsnx si2o9 solid solutions with cuspidine structure
    Japanese Journal of Applied Physics, 2007
    Co-Authors: Akinori Kan, Hirotaka Ogawa, Hitoshi Ohsato
    Abstract:

    The effects of Sn substitution for Zr on the Microwave Dielectric properties and crystal structure of Ca3(Zr1-xSnx)Si2O9 (CZSS) solid solutions were investigated in this study. The X-ray powder diffraction (XRPD) patterns of CZSS solid solutions were indicated to be a single phase, which corresponded to the cuspidine-type structure. The lattice parameters of CZSS solid solutions linearly decreased with increasing composition x, following Vegard's law. The Dielectric constant (er) of CZSS solid solutions slightly decreased from 10.6 to 8.4, whereas the quality factor (Qf) of the solid solutions increased from 54791 to 93296 GHz, depending on the composition x. As a result, the highest Qf value of 93296 GHz was obtained at x=1 where the Dielectric constant and temperature coefficient of resonant frequency were 8.4 and -64.7 ppm/°C, respectively. The decreases in the Dielectric constant and the increase in Qf values primarily depend on the composition x. This may be caused by the increase in the covalency of the (Zr,Sn)–O bond in the octahedron.

  • relationship between crystal structure and Microwave Dielectric properties of melilite type ceramic
    Journal of The European Ceramic Society, 2007
    Co-Authors: Atsushi Yokoi, Akinori Kan, Hirotaka Ogawa, Yoshifumi Nakamura
    Abstract:

    Abstract Crystal structure–Microwave Dielectric Property relations in the melilite-type Ba 2 (Mg 1− x Zn x )Si 2 O 7 ceramics were investigated in this study. The formation of a secondary phase was not detected over the whole composition range. Also, the lattice parameter, a , of the solid solutions decreased linearly with increasing the composition x , while the lattice parameter, c , was increased by the Zn substitution for Mg. Also, the covalency of the Mg O bond increased from 26 to 35% in the composition range of 0–0.75. Moreover, the covalency of the Zn O bond increased in the composition range of 0.25–1, while that of Si O bonds in the SiO 4 tetrahedron remained approximately constant over the whole composition range. The Dielectric constants ( ɛ r ) of the solid solutions were on the order of approximately 7.5, and the quality factors ( Q · f ) of the solid solutions increased with increasing the composition x . The temperature coefficient of resonant frequency ( τ f ) of the solid solutions varied from −62 to −74 ppm/°C with increasing the composition x ; therefore, the Zn substitution for Mg was not effective in improving the τ f value in this system.

  • crystal structure Microwave Dielectric Property relations in sm nb1 xtax ti1 yzry o6 ceramics
    Journal of The European Ceramic Society, 2006
    Co-Authors: Takeshi Oishi, Hitoshi Ohsato, Akinori Kan, Hirotaka Ogawa
    Abstract:

    Abstract The effects of the Ta substitution for Nb and the Zr substitution for Ti on the Microwave Dielectric properties and crystal structure of Sm(Nb 1− x Ta x )(Ti 1− y Zr y )O 6 ceramics were investigated in this study. The Sm(Nb 1− x Ta x )TiO 6 ( x  = 0–1) ceramics were single phase, whereas the limit of solid solutions for the SmTa(Ti 1− y Zr y )O 6 ceramics was y  = 0.4. In the case of the Sm(Nb 1− x Ta x )TiO 6 ceramics, the Dielectric constant and the temperature coefficient of resonant frequency were decreased, whereas the quality factor was increased by the Ta substitution for Nb. The maximum Q  ·  f value was obtained when the SmTaTiO 6 was synthesized, and the Microwave Dielectric properties are, ɛ r  = 37.6; τ f  = 24.2 ppm/°C; and Q  ·  f  = 24541 GHz. On the other hand, the Dielectric constants of the SmTa(Ti 1− y Zr y )O 6 ceramics were decreased from 37.6 to 28.9, whereas the quality factor was increased from 24541 to 38320 GHz with increasing composition y from 0 to 0.4. The temperature coefficient of resonant frequency of the ceramics varied from 24.2 to −11.6 ppm/°C. A near zero temperature coefficient of resonant frequency results from the composition of y  = 0.3 with a Dielectric constant of 31.1 and Q  ·  f value of 37481 GHz.

  • Microwave Dielectric Property microstructure relationships in y2ba cu1 xmg x o5 solid solutions
    Journal of The European Ceramic Society, 2004
    Co-Authors: Katsuhiro Mori, Hirotaka Ogawa, Akinori Kan, Hitoshi Ohsato
    Abstract:

    Abstract Y 2 Ba(Cu 1− x Mg x )O 5 solid solutions were synthesized by the solid state reaction method and the microstructure was studied by using SEM in order to clarify the Microwave Dielectric Property–structure relationship. From the variations in the lattice parameters obtained by Rietveld analysis and the least-squares method, it was clarified that the limit of Y 2 Ba(Cu 1− x Mg x )O 5 solid solutions is approximately at x =0.2. Grain growth and the reduction of porosity in the samples increased with the composition x . The Dielectric constants were constant and the quality factors were extremely increased from 3800 to 42 300 GHz, as the composition x increased from 0 to 0.2. Thus, it was found that the quality factors of the samples were closely related to the morphological changes and a formation of the porosity; the temperature coefficient of resonant frequency of the samples ranged from −35.0 to −56.5 ppm/°C. Moreover, compared to Y 2 Ba(Cu 1− x Mg x )O 5 compound without cold isotropic pressure (CIP), that with CIP especially exhibited approximately 16% higher Q · f value.

Atsushi Yokoi - One of the best experts on this subject based on the ideXlab platform.

  • relationship between crystal structure and Microwave Dielectric properties of melilite type ceramic
    Journal of The European Ceramic Society, 2007
    Co-Authors: Atsushi Yokoi, Akinori Kan, Hirotaka Ogawa, Yoshifumi Nakamura
    Abstract:

    Abstract Crystal structure–Microwave Dielectric Property relations in the melilite-type Ba 2 (Mg 1− x Zn x )Si 2 O 7 ceramics were investigated in this study. The formation of a secondary phase was not detected over the whole composition range. Also, the lattice parameter, a , of the solid solutions decreased linearly with increasing the composition x , while the lattice parameter, c , was increased by the Zn substitution for Mg. Also, the covalency of the Mg O bond increased from 26 to 35% in the composition range of 0–0.75. Moreover, the covalency of the Zn O bond increased in the composition range of 0.25–1, while that of Si O bonds in the SiO 4 tetrahedron remained approximately constant over the whole composition range. The Dielectric constants ( ɛ r ) of the solid solutions were on the order of approximately 7.5, and the quality factors ( Q · f ) of the solid solutions increased with increasing the composition x . The temperature coefficient of resonant frequency ( τ f ) of the solid solutions varied from −62 to −74 ppm/°C with increasing the composition x ; therefore, the Zn substitution for Mg was not effective in improving the τ f value in this system.

  • low temperature sintering Microwave Dielectric Property relations in ba3 vo4 2 ceramic
    Journal of Alloys and Compounds, 2006
    Co-Authors: Ryosuke Umemura, Hirotaka Ogawa, Atsushi Yokoi, Hitoshi Ohsato
    Abstract:

    Abstract The Ba 3 (VO 4 ) 2 – x  wt.%B 2 O 3 ( x  = 0–5) ceramics were prepared by the solid state reaction method in order to reduce the sintering temperature. The saturated bulk densities of Ba 3 (VO 4 ) 2 – x  wt.%B 2 O 3 ceramics were shifted toward lower sintering temperatures with increased the amounts of B 2 O 3 doping, and then an improvement in the quality factor ( Q · f ) of the samples was recognized at the lower sintering temperatures. As a result, the Q · f value of 41,065 GH, the ɛ r of 12.5 and the τ f value of 38.8 ppm/°C were obtained in the sample of the Ba 3 (VO 4 ) 2 –0.5 wt.%B 2 O 3 ceramic sintered at the temperature of 950 °C. However, the Q · f values of the sample with B 2 O 3 higher than that of 3 wt.% additions decreased because of the formation of secondary phase and abnormal grain growth of the sample. As for the chemical compatibility with silver, no secondary phase was detected in the XRPD pattern when the mixtures of Ba 3 (VO 4 ) 2 –1 wt.%B 2 O 3 ceramics and Ag powders were heat-treated at 900 °C for 1 h in air.

Yoshifumi Nakamura - One of the best experts on this subject based on the ideXlab platform.

  • relationship between crystal structure and Microwave Dielectric properties of melilite type ceramic
    Journal of The European Ceramic Society, 2007
    Co-Authors: Atsushi Yokoi, Akinori Kan, Hirotaka Ogawa, Yoshifumi Nakamura
    Abstract:

    Abstract Crystal structure–Microwave Dielectric Property relations in the melilite-type Ba 2 (Mg 1− x Zn x )Si 2 O 7 ceramics were investigated in this study. The formation of a secondary phase was not detected over the whole composition range. Also, the lattice parameter, a , of the solid solutions decreased linearly with increasing the composition x , while the lattice parameter, c , was increased by the Zn substitution for Mg. Also, the covalency of the Mg O bond increased from 26 to 35% in the composition range of 0–0.75. Moreover, the covalency of the Zn O bond increased in the composition range of 0.25–1, while that of Si O bonds in the SiO 4 tetrahedron remained approximately constant over the whole composition range. The Dielectric constants ( ɛ r ) of the solid solutions were on the order of approximately 7.5, and the quality factors ( Q · f ) of the solid solutions increased with increasing the composition x . The temperature coefficient of resonant frequency ( τ f ) of the solid solutions varied from −62 to −74 ppm/°C with increasing the composition x ; therefore, the Zn substitution for Mg was not effective in improving the τ f value in this system.