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1.
M. Aoyama J. Temuujin M. Senna T. Masuko C. Ando H. Kishi 《Journal of Electroceramics》2006,17(1):61-64
Z-type hexaferrites (Ba3(1 − x)Sr3x
Co2Fe24O41with x = 0–0.5, Z-hex) were prepared in a nearly phase pure state by a two-step calcination with an intermediate wet milling. The
first calcination of the starting mixture comprising oxides or hydroxides at temperatures below 1100∘C brought about a mixture of layer-structured M and Y-type hexaferrite phases, together with a spinel phase of Co ferrite.
Z-hex was fully crystallized after the second calcination up to 1230∘C. Wet milling between the two calcination steps was decisive for the phase purity. Emphasis was laid on the quantitative
analyses of Z-hex, together with the evaluation of anisotropic growth of the crystallites. Sr addition stabilizes Z-hex, while
decreases degree of anisotropy simultaneously. 相似文献
2.
Fransiska Cecilia Kartawidjaja Zhaohui Zhou John Wang 《Journal of Electroceramics》2006,16(4):425-430
Heterolayered Pb(Zr1 − x
Ti
x
)O3 thin films consisting of alternating PbZr0.7Ti0.3O3 and PbZr0.3Ti0.7O3 layers were successfully deposited via a multistep sol-gel route assisted by spin-coating. These heterolayered PZT films,
when annealed at a temperature in the range of 600–700∘C show (001)/(100) preferred orientation, demonstrate desired ferroelectric and dielectric properties. The most interesting
ferroelectric and dielectric properties were obtained from the six-layered PZT thin film annealed at 650∘C, which exhibits a remanent polarization of 47.7 μC/cm2 and a dielectric permittivity of 1002 at 100 Hz. Reversible polarization constituents a considerably high contribution towards
the ferroelectric hysteresis of the heterolayered PZT films, as shown by studies obtained from C-V and AC measurement. 相似文献
3.
ZnNb2O6-TiO2 mixture thin films with multilayer structures were fabricated via a sol-gel spin coating process. TiO2 layers were deposited on the pre-crystallized ZnNb2O6 layers in order to suppress the formation of the ixiolite phase which always forms in the bulk system. The phase constitution
of the thin films, confirmed by X-ray diffraction (XRD), could be controlled by the annealing temperatures, which, in turn,
influenced the dielectric properties of the thin films. TiO2 layers crystallized as the anatase phase and then transformed to the rutile phase at temperatures higher than 725∘C. Dielectric constants of the mixture thin films, measured at 1 MHz with an MIM (metal-insulator-metal) structure, increased
from 27 to 41 with dielectric losses below 0.005 as the annealing temperature increased from 700∘C to 900∘C. The increase in the dielectric constants was understood to originate from the increasing amounts of the rutile phase. Temperature
coefficients of capacitance (TCC) were also measured between 25∘C and 125∘C, which showed a decreasing manner from positive values to negative values with increasing annealing temperatures. When annealed
at 850∘C, the TCC of the thin films could be tuned to be approximately 0 ppm/oC with dielectric constant and dielectric loss of 36 and 0.002, respectively. 相似文献
4.
I. H. Kim D. Y. Ku J. H. Ko D. Kim K. S. Lee J.-h. Jeong T. S. Lee B. Cheong Y.-J. Baik W. M. Kim 《Journal of Electroceramics》2006,17(2-4):241-245
To improve the stability of sputter-deposited ZnO:Al (AZO) films at high temperature above 300∘C, an amorphous Zn-Sn-O (ZTO) film was deposited on the top of AZO films as an protective layer by co-sputtering of pure ZnO
and SnO2 targets. Amorphous ZTO films had resistivity in the range from 10−2 to 10−3 Ωcm and were stable up to temperature of 400∘C. Heat treatments of bare AZO films in the atmosphere at 400∘C resulted in a dramatic increase in the resistivity accompanied by substantial decrease in carrier concentration and Hall
mobility. The AZO films covered with the ZTO film showed remarkable improvement in thermal stability for subsequent heat treatments
in the temperature range from 200 to 400∘C in the atmosphere as well as chemical stability in weak acidic solution. X-ray photoelectron spectroscopy analysis showed
that the improvement was attained by ZTO layer acting as diffusion barrier of oxygens and/or water vapors. 相似文献
5.
Acceptor doped-ceria is a possible electrolyte material for the IT-SOFC (intermediate temperature solid oxide fuel cell) due
to its high oxygen-ion conductivity. However, its use has been limited by its mechanical weakness and the appearance of electronic
conductivity in reducing condition. In this study, alumina was selected as an additive in the doped-ceria to see if it increases
the oxygen-ion conductivity and mechanical strength. Effects of alumina addition in doped ceria were studied as a function
of alumina content and acceptor (Gd) content.
The electrical conductivity of (Ce1−x
Gd
x
O2−δ)1−y
+ (Al2O3)
y
(x = 0–0.35, y = 0–0.10) was measured by using impedance spectroscopy. The grain conductivity of Ce0.8Gd0.2O2-δ (GDC20) with 5 mol% alumina increased ∼3 times from that of GDC20 at 300∘C. The grain conductivity was even ∼2 times higher than that of Ce0.9Gd0.1O2−δ (GDC10) at 300∘C. The electrical conductivity of GDC20 without alumina addition, measured at 500∘C in air, rapidly decreased after exposure to reducing condition (Po2∼10−22 atm) at 800∘C. However, the decrease was much slower in GDC20 with alumina addition, indicating the improved mechanical strength.
Among the examined compositions, (Ce0.75Gd0.25 O2-δ)0.95 + (Al2O3)0.05 (GDC25A5) showed the highest conductivity at most temperatures. 相似文献
6.
A. N. Baranov G. N. Panin Masahiro Yoshimura Young-Jei Oh 《Journal of Electroceramics》2006,17(2-4):847-852
ZnO nanorods synthesized at 700∘C by heating the mixture of solution processed Zn precursor with NaCl−Li2CO3 salt were examined. The size of the nanorods was in the range of 15–100 nm in diameter and 0.5–5 μm in length. The nanorods
show the single crystal structure being free from second phases. The Mn and MnSn-doped nanorods by demonstrated ferromagnetic
properties and unique luminescence properties due to doping and charge carrier confinement effects. Magnetic susceptibility
of the samples as a function of temperature shows Curie–Weiss behavior. Hysteresis with the coercive field <200 Oe was clearly
observed in magnetization versus field curves at 5 and 300 K. Increasing the Mn concentration increases significantly the
magnetic hysteresis. 相似文献
7.
The amorphous films were annealed in a wide temperature range (250–1000∘C) and film properties of TiO2 thin films were studied. Nano-sized anatase polycrystallites had been induced by thermal annealing for the films annealed
at and above 300∘C as confirmed by X-ray diffraction. Strong LO-phonon Raman modes, especially B1g
(395 cm−1) and E
g
(636 cm−1) in Raman spectra and the absorption peak at 436 cm−1 in absorbance spectra by Fourier transform infrared spectroscopy also indicated the existence of anatase phase in crystalline
thin films. In addition, with the increase of the annealing temperature, the wettability of the film surface was enhanced
as shown by the decrease of water contact angle from over 90∘ to less than 40∘. Moreover, upon UV laser irradiation on film surface, the water contact angle saturated at 10∘ indicative of a highly hydrophilic surface for all the films, which arose from the dissociative adsorption of water molecules
on the defect sits of the surface generated by the photocatalysis reactions of TiO2. This behavior makes the film a good potential candidate for self-clean coatings. 相似文献
8.
Jong-Hee Kim Dong-Hyun Peck Rak-Hyun Song Gil-Young Lee Dong-Ryul Shin Sang-Hoon Hyun Jürgen Wackerl Klaus Hilpert 《Journal of Electroceramics》2006,17(2-4):729-733
Synthesis and sintering properties of the (La0.8Ca0.2−x
Sr
x
)CrO3 samples doped by two alkaline earth metals in comparison to the doped only by one alkaline earth metal were evaluated by
phase analysis, sintering properties, thermal expansion behaviors, and electrical conductivity. The sintered (La0.8Ca0.2−x
Sr
x
)CrO3 (x = 0, 0.05, and 0.1) and (La0.8Ca0.2−x
Sr
x
)CrO3 (x = 0.2) were found to have orthorhombic and rhombohedral symmetries, respectively. Relative density of the (La0.8Sr0.2)CrO3 sample sintered at 1500∘C for 5 h was lower than that of the (La0.8Ca0.2−x
Sr
x
)CrO3 (x = 0, 0.05, and 0.1) sample. TECs of the (La0.8Ca0.2−x
Sr
x
)CrO3 (x = 0, 0.05, 0.1, and 0.2) in air were 11 × 10−6/∘C, 11.2 × 10−6/∘C, 11.2 × 10−6/∘C, and 11.3 × 10−6/∘C, respectively. The electric conductivity of the (La0.8Ca0.2−x
Sr
x
)CrO3 sample was determined. 相似文献
9.
Jae Chun Lee Hyuk Chun Kwon Yong-Pil Kwon Sung Park Hae-Won Lee Jong-Ho Lee Joosun Kim 《Journal of Electroceramics》2006,17(2-4):1109-1111
Porous ceramic fiber composites were coated with pyrolytic carbon by the decomposition of either propane or infiltrated phenolic
resin in a nitrogen atmosphere at 800–900∘C. The amount of carbon coating was varied to tailor the electrical conductivity of the carbon-coated composites. The electrical
and thermal conductivity of the composites were measured at room temperature using a two-point method and a hot-wire one,
respectively. Up to 30 wt% pyrolytic carbon, the electrical conductivity σ showed linearly increasing tendency and was fitted
by the effective conductivity according to the parallel rule of a mixture σ =ΣV
i⋅σi with an effective conductivity of pyrolytic carbon σc and volume fraction of coated carbon V
c. The electrical conductivity of coated carbons prepared from propane at 900∘C and phenolic resin at 800∘C was of the order of 100 and 10−1 S cm−1, respectively. 相似文献
10.
Ferroelectric Ba0.5Sr0.5TiO3 (BST) films were prepared on Pt/Ti/SiO2/Si substrates by the sol-gel process. The films were spin-coated at 2000 rpm for 30 secs and then pyrolysed for 5 mins at
the temperature of 350∘C. This coating procedure was repeated for 3, 4, 5 and 6 times to obtain BST films with different thicknesses. After coating
the films with the desired repetition times, the films were finally annealed in a conventional furnace at temperatures ranging
from 600∘C to 800∘C with a 50∘C interval in between. The films obtained with an annealing procedure of 750∘C were polycrystalline with the presence of an impurity BaCO3 phase. The capacitance and leakage current were measured and used to extract information on the metal-BST interface. With
the series capacitance model and modified Schottky emission equation, the thickness of the dead layers for Au/BST and Pt/BST
interfaces were calculated to be less than 6 nm and 5 nm, respectively. 相似文献
11.
Films of (1−x)Pb(Zn1/3Nb2/3)O3-xPb(Zr0.4Ti0.6) O3 (x = 0.6, 40PZN-60PZT) were deposited on Pt/TiO2/ SiO2/Si substrate through spin coating. Using a combination of homogeneous precursor solution preparation and two-step pyrolysis
process, we were able to obtain the 40PZN-60PZT thin films of perovskite phase virtually without pyrochlore phase precipitation
after annealing above 650∘C. But since annealing done at the high temperatures for extended time can cause diffusion of Pt, TiO2 and Si, and precipitation of nonstoichiometric PbO, we adopted 2-step annealing method to circumvent these problems. The
2-step annealed films show dense microstructure than the 1-step films annealed at higher temperature. Furthermore, the root-mean-square
surface roughness of 220 nm thick films which are annealed at 720∘C for 1 min and then annealed at 650∘C for 5 min was found to be 3.9 nm by atomic force microscopy as compared to the 12 nm surface roughness of the film annealed
only at 720∘C for 5 min. The electrical properties of 2-step annealed films are virtually same and those of the 1-step annealed films
annealed at high temperature. The film 2-step annealed at 720∘C for brief 1 min and with subsequent annealing at 650∘C for 5 min showed a saturated hysteresis loop at an applied voltage of 5 V with remanent polarization (P
r) and coercive voltage (V
c) of 25.3 μC/cm2 and 0.66 V respectively. The leakage current density was lower than 10−5A/cm2 at an applied voltage of 5 V. 相似文献
12.
P-type thermoelectric Bi0.5Sb1.5Te3 compounds were prepared by the spark plasma sintering method with temperature ranges of 300–420∘C and powder sizes of ∼75 μm, 76–150 μm, 151–250 μm. As the sintering temperature increased, the electrical resistivity and
thermal conductivity of the compound were greatly changed due to an increase in the relative density. The Seebeck coefficient
and electrical resistivity were varied largely with decreasing the powder size. Subsequently, the compound sintered at 380∘C with the powders of ∼75 μm showed the maximum figure-of-merit of 2.65 × 10−3K−1 and the bending strength of 73 MPa. 相似文献
13.
Doped ceria (CeO2) compounds are fluorite type oxides, which show oxide ionic conductivity higher than yttria stabilized zirconia, in oxidizing
atmospheres. As a consequence of this, considerable interest has been shown in application of these materials for `low (500∘–650∘C)’ temperature operation of solid oxide fuel cells (SOFCs). In this study, some rare earth (eg. Gd, Sm, and Dy) doped CeO2 nano-powders were synthesized via a carbonate co-precipitation method. Fluorite-type solid solution were able to be formed
at low temperature, such as 400∘C and dense sintered bodies were subsequently fabricated in the temperature ranging from 1000∘ to 1450∘C by conventional sintering (CS) method. To develop high quality solid electrolytes, the microstructure at the atomic level
of these doped CeO2 solid electrolytes were examined using transmission electron microscopy (TEM). The specimens obtained by CS had continuous
and large micro-domains with a distorted pyrochlore structure or related structure, within each grain. We conclude that the
conducting properties in these doped CeO2 systems are strongly influenced by the micro-domain size in the grain. To minimize the micro-domain size, spark plasma sintering
(SPS) was examined. SPS has not been used to fabricate dense sintered bodies of doped CeO2 electrolytes, previously; carbon from the graphite dies penetrates the specimens and inhibits densification. To overcome
this challenge, and to be able to produce dense sintered bodies of doped CeO2 of a grain size that minimizes the microdomain growth, a combination of SPS and CS methods were examined. Using this combined
method we report that we were able to produce fully dense specimens with improved conductivity. This is correlated with a
reduction in the size of the micro-domains. Consequently we conclude that the control of micro-domain size within the grain
structure is a key component in the successful design of electrolyte materials with improved conductivity. 相似文献
14.
ZnGa2O4 thin film phosphors have been synthesized on ITO coated glass and soda-lime glass at a firing temperature of 500∘C and an annealing temperature of 500∘C and 600∘C via a chemical solution method using Zinc acetate dihydrate, Gallium nitrate hydrate and 2-methoxiethanol as a solution.
XRD patterns of the film phosphors synthesized showed the peaks of ZnGa2O4 crystalline phases. AFM surface morphologies of the ZnGa2O4 thin film phosphors revealed marked differences according to an annealing temperature of 500∘C and 600∘C under an annealing atmosphere (3% H2/Ar). On the other hand, the sheet resistance of ZnGa2O4 thin film phosphors, which were measured by four-point probe instrument, was approximately 5.76 Ω /square and 7.86 Ω /square
with annealing temperature, respectively. The ZnGa2O4 thin film phosphors exhibited blue emission spectra with peak wavelength of 434 nm and 436 nm by ultra-violet excitation
around 230 nm. 相似文献
15.
The efficiency of simultaneous application of chemically-derived starting powders and melt-forming sintering aids in low temperature
sintering has been demonstrated. Doping of cryochemically processed BiNbO4 powders with CuO/V2O5 causes reducing sintering temperatures from 850–900∘C to 700–720∘C. Similar doping of Zn3Nb2O8 fine powders allows to obtain ceramics with density 97–98% and Q × F values up to 40 000 GHz at T > 720∘C. The sintering of solution-derived BaCeO3 powders doped with CuO results in dense ceramics at T = 1000∘C. Morphological evolution during sintering was observed using hot stage SEM. Low temperature liquid phase sintering of fine
powders is rather sensitive to the traces of secondary phases and to the micromorphology of starting powders though observed
reduction of sintering temperatures is substantially larger than for traditional liquid phase sintering of coarse-grained
oxide powders. 相似文献
16.
Wataru Sakamoto Yu-ki Mizutani Naoya Iizawa Toshinobu Yogo Takashi Hayashi Shin-ichi Hirano 《Journal of Electroceramics》2006,17(2-4):293-297
Ferroelectric Si-doped (Bi,Nd)4Ti3O12 thin films have been prepared on Pt/TiOx/SiO2/Si substrates through metal-organic compounds by the chemical solution deposition. The Bi3.25Nd0.75Ti2.9Si0.1O12 (BNTS) precursor films were found to crystallize into the Bi-layered perovskite Bi4Ti3O12 single-phase above 600∘C. The synthesized BNTS films revealed a random orientation having a strong 117 reflection. The BNTS thin films prepared between
600∘C and 700∘C showed well-saturated P-E hysteresis loops with P
r of 13–14 μ C/cm2 and E
c of 100–110 kV/cm at an applied voltage of 5 V. The surface roughness of the BNTS thin films was improved by Si doping compared
with that of undoped Bi3.35Nd0.75Ti3O12 films. 相似文献
17.
Yi-Cheng Liou Jen-Hsien Chen Yi-Chen Huang Chi-Ting Wu Yow-Renn Chen 《Journal of Electroceramics》2006,16(3):213-220
Pb(Ni1/3Nb2/3)0.72Ti0.28O3 (PNNT) perovskite ceramics produced by a reaction-sintering process were investigated. Without any calcination, the mixture
of PbO, Ni(NO3)2, Nb2O5 and TiO2 was pressed and sintered directly into PNNT ceramics. PNNT ceramics of 100% perovskite phase were obtained. For PNNT sintered
for 2 h in PbO compensated atmosphere, maximum density reaches a value 8.49 g/cm3 (99.8% of the theoretical value) at 1250∘C. A maximum dielectric constant 20600 occurred around 37∘C at 1 kHz in PNNT sintered at 1250∘C for 2 h. 相似文献
18.
Jeong-Ryeol Kim Geun-Kyu Choi Dong Kyun Yim Jong-Sung Park Kug Sun Hong 《Journal of Electroceramics》2006,17(1):65-69
Glasses in the ZnO-B2O3-MO3(M = W, Mo) ternary were examined as potential replacements to PbO-B2O3-SiO2-ZnO glass frits with the low firing temperature (500–600∘C) for the dielectric layer of a plasma display panels (PDPs). Glasses were melted in air at 950–1150∘C in a narrow region of the ternary using standard reagent grade materials. The glasses were evaluated for glass transition
temperature (T
g
), softening temperature (T
d
), the coefficient of thermal expansion (CTE), dielectric constant (ε
r
), and optical property. The glass transition temperature of the glasses varied between 470 and 560∘C. The coefficient of thermal expansion and the dielectric constant of the glasses were in the range of 5–8 × 10− 6/∘C and 8–10, respectively. The addition of MO3to ZnO-B2O3binary could induce the expansion of glass forming region, the reduction of T
g
and the increase in the CTE and the dielectric constant of the glasses. Also, the effect of the addition of MO3to ZnO-B2O3binary on the transmittance in the visible-light region (350–700 nm) was investigated. 相似文献
19.
Ni-Cu-Zn ferrites of composition Ni1 − x − yCuyZnxFe2O4 with 0.4 ≰ x ≰ 0.6 and 0 ≰ y ≰ 0.25 were prepared by standard ceramic processing routes. The density of samples sintered at 900^∘C increases with copper
concentration y. Dilatometry reveals a significant decrease of the temperature of maximum shrinkage with y. The permeability has maximum values of μ = 500–1000 for x = 0.6. The Curie temperature is sensitive to composition and changes form about 150^∘C for x = 0.6 to Tc > 250^∘C for x = 0.4, almost independent on the Cu-content. A small iron deficiency in Ni0.20Cu0.20Zn0.60 + zFe2 − zO4 − (z/2) with 0 ≰ z ≰ 0.06 significantly enhances the density of samples sintered at 900^∘C. The maximum shrinkage rate is shifted to T < 900∘C. These compositions are therefore appropriate for application in low temperature co-firing processes. The permeability is
reduced with z, hence a small z = 0.02 seems to be the optimum ferrite composition for high sintering activity and permeability. 相似文献
20.
High-performance pyroelectric infrared detectors have been fabricated using Lithium tantalite (LiTaO3) thin films deposited on Pt(111)/Ti/SiO2/Si(100) substrates by diol-based sol-gel method and rapid thermal annealing (RTA) technique. The dielectric and pyroelectric
properties of IR detectors of LiTaO3 thin films crystallized by conventional and RTA processes are investigated. Experimental results reveal that the heating
rate will influence strongly on dielectricity and pyroelectricity of LiTaO3 thin films. The voltage responsivities (Rv) measured at 80 Hz increase from 5496 to 8455 V/W and the specific detecivities
(D∗) measured at 300 Hz increase from 1.94 × 108 to 2.38 × 108 cmHz1/2/W with an increase of heating rate from 600 to 1800∘C/min. However, the voltage responsivity and the specific detecivity decrease with heating rate in excess of 1800∘C/min. The results show that the LiTaO3 thin film detector with a heating rate of 1800∘C/min exists both the maximums of voltage responsivity and specific detecivity. 相似文献