共查询到20条相似文献,搜索用时 46 毫秒
1.
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
2.
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
3.
Yong Soo Cho Dong Joo Shin In June Kim Hyung Sub Lee Dong Suck Jeong 《Journal of Electroceramics》2006,17(2-4):461-465
The mixed system of BaTiO3 and AlN has been investigated in terms of dielectric properties and microstructure. Two different types of additives, bismuth
oxide and bismuth borosilicate glass, were used to lower sintering temperature. First, the addition of a fixed content (3
wt.%) of Bi2O3 provided densification at 1200∘C where monotonous decreases of dielectric constant were found with increasing the content of AlN. On the other hand, the
bismuth borosilicate glass was effectively used to decrease firing temperature to 850∘C, which is suitable for thick film capacitor applications. A practical demonstration of thick film capacitors using a Ag
electrode on a 96% alumina substrate indicated that the optimum composition of 76BaTiO3-20AlN-4glass may be adequate for generating k of 79.4 and tan δ of 0.014 at 1 MHz as a result of the low temperature firing
of 850∘C in air atmosphere. 相似文献
4.
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
5.
This study examined the effect of spark plasma sintering (SPS) on the densification behavior and resulting dielectric and
piezoelectric properties of Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 ceramics with a 5 mol% excess of PbO. Through normal sintering at 1200∘C, the density of the specimen reached only 92% of the theoretical density (TD). However, with the SPS treatment, the density
of the PMN-PT ceramics increased to more than 99% of the TD at 900∘C, and maintained over 98% of the TD during subsequent heat-treatment at 1200∘C for 10 h. The increased density of the Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 ceramics resulted in an improvement in the dielectric and piezoelectric properties. The SPS treatment was also successfully
applied to the densification of a PMN-PT single crystal grown on a BaTiO3 seed crystal using a solid-state crystal growth (SSCG) process. 相似文献
6.
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
7.
Thin films of Pb(Mg1/3,Nb2/3)O3 (PMN) and Pb(Mg1/3,Nb2/3)O3-PbTiO3 (PMN-PT) were fabricated on Si and Pt/Ti/SiO2/Si substrates by MOCVD using ultrasonic nebulization and their characteristics were investigated. PMN-PT films deposited
at 350∘C were annealed in a RTA (Rapid Thermal Annealing) system at 650∘C for 30 sec to improve the micostructural properties. The crystallographic properties of PMN-PT films strongly depend on
the content ratio of PbTiO3. The content of pyrochlore phase in PMN-PT films decreased with the increase of Ti content and nearly single phase perovskite
films were obtained at the composition of 80PMN-20PT. The PMN-PT films with perovskite phase showed a typical butterfly type
C-V curve which verifies the ferroelectricity and had the relative dielectric constant of about 60. 相似文献
8.
H. Asakura C. D. Madhusoodana Y. Kameshima A. Nakajima K. Okada 《Journal of Electroceramics》2006,17(1):31-36
Faujasite-type zeolite films were prepared on foamed stainless steel by the in-situ crystallization method. Precursor solutions
were prepared by dissolving water glass and NaAlO2in a NaOH solution and aged at room temperature for two days. The concentrations of the starting materials were varied from
0.29 to 2.3 M (in SiO2concentration) keeping the molar ratios of Na2O:SiO2:Al2O3fixed at 3.6:3.0:1.0. The foamed stainless steel substrate had about 90% of porosity and an average pore size of 600 μ m. It was dip-coated in the precursor solution four times, then hydrothermally treated at 80∘, 110∘ and 150∘C for 6–48 h. The XRD patterns and SEM photographs revealed that faujasite-type zeolite was formed predominantly at a SiO2concentration of 1.1 M, temperature of 110∘C and duration of 24 h, with a product particle size of 2–5 μ m. At higher concentrations of the precursor solution, hydroxylsodalite becomes the major product rather than faujasite-type
zeolite. The adherence strength of the zeolite grains deposited on the foamed stainless steel is higher in the in-situ crystallization
method than when a conventional solution method is used. Thus, the in-situ crystallization method is concluded to be effective
for preparing zeolite films even on metal substrates. 相似文献
9.
Sang-Hoon Shin Sung-Dae Kim Jong-Ha Moon Jin-Hyeok Kim 《Journal of Electroceramics》2006,17(2-4):1097-1101
Er3+/Pr3+ co-doped soda-lime glass thin films have been fabricated using RF magnetron sputtering method and their structural and optical
properties have been studied. Deposition rate, crystallinity, and composition of glass thin films were investigated by scanning
electron microscopy, transmission electron microscopy, and electron probe micro area analysis. Refractive index, birefringence
and binding characteristics have been investigated using a prism coupler and X-ray photoelectron spectroscopy. Er3+/Pr3+ co-doped soda lime glass thin films were prepared by changing substrate temperature (room temp. ∼550∘C), RF power (90 W–130 W), and Ar/O2 gas flow ratio at processing pressure of 4 mTorr. Glass thin films could be obtained at the optimized processing condition
at 350∘C, RF power of 130 W, and gas flow of Ar:O2 = 40:0 with maximum deposition rate of 1.6 μm/h. Refractive index and birefringence increased from 1.5614 to 1.5838 and from
0.000154 to 0.000552, respectively, as the content of Pr3+ increased. Binding energy of Pr3d also increased as the content of Pr3+ increased. 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.
Ahmed Mohamed El-Toni Shu Yin Yuichiro Hayasaka Tsugio Sato 《Journal of Electroceramics》2006,16(1):9-14
White nanoparticles of calcia-doped ceria were prepared from the precipitate by reacting CeCl3-CaCl2mixed solution with NaOH solution at pH 12 and the oxidation with hydrogen peroxide solution at 40∘C, followed by the calcination at 700∘C for 1 h. The sample before calcination contained significant amount of OH− in the lattice and was yellow, but the powders calcined above 700∘C were white, indicating that cation defect formed by replacing O2 − with OH− played as the color center. It is confirmed that calcia-doped ceria showed much lower photocatalytic activity as well as
lower generation of singlet oxygen under UV light irradiation than those with titania and zinc oxide. Calcia-doped ceria particles
were coated with amorphous silica by means of sol-gel reaction technique using hydrolysis of tetraethylorthosilicate (TEOS)
or acid hydrolysis of sodium silicate. The silica coating by sol-gel reaction with TEOS was much more efficient for the reduction
of catalytic activity of ceria for the oxidation of organic materials without loss of UV-shielding ability than that by acid
hydrolysis of sodium silicate. 相似文献
12.
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
13.
A systematic investigation of cerium and stannum doped 0.94(Bi0.5Na0.5)TiO3−0.06BaTiO3 (Sn&Ce-BNT6BT) based lead-free piezoelectric ceramics is undertaken to understand the influence of sintering temperature
on electrical properties. The X-ray diffraction patterns showed that all of the Sn&Ce-BNT6BT ceramics exhibited a single perovskite
structure with the co-existence of the rhombohedral and tetragonal phase. The smaller grain size of Sn&Ce-BNT6BT ceramics
was obtained at lower sintering temperature, and more cubical grains of Sn&Ce-BNT6BT ceramics were obtained at higher sintering
temperature. The temperature dependence of dielectric permittivity of the compositions exhibited strong dispersion with the
increasing temperature, and the dielectric loss tangent increased dramatically while the temperature over 225∘C. The depolarization temperature T
d
of Sn&Ce-BNT6BT ceramics sintered at 1160∘C was 92.6∘C. The remnant polarizations P
r
for Sn&Ce-BNT6BT ceramics sintered at 1120 and 1200∘C were found to be 28.8 and 33.4 μC/cm2 at room temperature, respectively. 相似文献
14.
Youngha Kim Sungkwan Kim Young-Ah Jeon Yunseok Kim Hanjong Paik Yangsoo Kim Sang-Chul Han Young-Hee Han Nyeon-Ho Jeong Tae-Hyun Sung Jong-In Hong Kwangsoo No 《Journal of Electroceramics》2006,17(2-4):1063-1067
YBa2Cu3Ox (Y123) superconducting films were fabricated on Cu substrates using a simple screen-printing method, from Cu-free powders
(Y2O3 and BaCO3). In the process, CuO, which causes superconducting properties of Y123 films to deteriorate, was formed on the film surface.
By varying the atomic ratio of Y to Ba (Y:Ba = 1:1∼1:4), the ratio needed to prevent CuO formation was found for the film
surface that had been heat-treated at 980∘C for 17 s. The film, with the ratio of Y to Ba (Y:Ba = 1:1), is reheat-treated at 930∘C for 9 min 30 s to form a superconducting Y123 phase. It was possible to prevent CuO formation by controlling the ratio of
Cu-free powders in the mixture and to fabricate YBCO superconductors on Cu substrates using a two-step heat-treatment. 相似文献
15.
MEMS structures for micro gas sensors had advantage for lower power consumption, reducing size, and easily making cavity structures.
Also, co-planar type MEMS structures (CPMS) for gas sensors with low power consumption heater and dispensed sensing materials were newly proposed and
investigated. CPMS, which were formed with micro heater and sensing electrodes at the same layer, to reduce process steps,
diffusions between upper layer and lower layer, and thermal differences between the center and the periphery of the sensing
layer compared with stacked structure. Dispensing method guided by back-side etched well was good for forming sensing material
on sensing electrode and had advantage that various sensing materials could be applied for array type sensors. CPMS were fabricated
on four-inch diameter and double side polished (100) silicon wafers and using anisotropic bulk silicon micromachining for
membrane formation and etched well. A size of chips with 1.15 mm × 1.15 mm membrane was 4.8 mm × 4.8 mm. And co-planar type
sensing electrodes were located in the middle of low stress SiO2/Si3N4 (400 nm /1 μm) membranes. Membranes are thermally isolated from the chip frame because they have low thermal conductivity,
generally. Temperatures were measured using IR thermometer with linearly increasing applied power. Power consumption at 400∘C was 150 mW. Membranes of CPMS were withstood up to 730∘C at the power of 350 mW. Characteristics of micro heaters for various heater widths of 50 μm, 75 μm, 100 μm and ratios of
membrane dimension to heater dimension were measured. Sensing materials guided by micromachined well were dispensed on sensing
electrodes. CPMS were mounted on a TO-8 package. From these results, fabricated and characterized CPMS could be used for applications
in portable gas sensors for detection of CO, NOx, CHx, H2S, and so on. 相似文献
16.
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
17.
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
18.
C. K. Tan Gregory K. L. Goh D. Z. Chi Albert C. W. Lu B. K. Lok 《Journal of Electroceramics》2006,16(4):581-585
Polycrystalline BaTiO3 films were hydrothermally grown on Ti-coated substrates from 80∘C to 200∘C. Films grown at 200∘C exhibited the lowest dielectric loss of around 0.1. Proton incorporation was more severe for the 80∘C film resulting in higher dielectric losses and leakage currents about two orders of magnitude higher. Post deposition oxygen
plasma treatment removed incorporated protons and reduced the loss tangent but did not reduce defect density. As such, the
leakage current of the 80∘C film remained high. The films had dielectric constants of 275 to 675 from 100 Hz to 100 kHz and a value of 67 from 100 MHz
to 3 GHz. 相似文献
19.
Jong-Bong Lim Sahn Nahm Hyo-Tae Kim Jong-Hee Kim Jong-Hoo Paik Hwack-Joo Lee 《Journal of Electroceramics》2006,17(2-4):393-397
The effect of B2O3 and CuO on the sintering temperature and microwave dielectric properties of BaTi4O9 ceramics was investigated. The BaTi4O9 ceramics were able to be sintered at 975∘C when B2O3 was added. This decrease in the sintering temperature of the BaTi4O9 ceramics upon the addition of B2O3 is attributed to the formation of BaB2O4 second phase whose melting temperature is around 900∘C. The B2O3 added BaTi4O9 ceramics alone were not sintered below 975∘C, but were sintered at 875∘C when CuO was added. The formation of BaCu(B2O5) second phase could be responsible for the decrease in the sintering temperature of the CuO and B2O3 added BaTi4O9 ceramics. The BaTi4O9 ceramics containing 2.0 mol% B2O3 and 5.0 mol% CuO sintered at 900∘C for 2 h have good microwave dielectric properties of εr = 36.3, Q× f = 30,500 GHz and τf = 28.1 ppm/∘C 相似文献
20.
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