共查询到20条相似文献,搜索用时 15 毫秒
1.
Toshinobu Yogo Wataru Sakamoto Tadayuki Isaji Koichi Kikuta Shin-ichi Hirano 《Journal of the American Ceramic Society》1997,80(7):1767-1772
Transparent and highly oriented Ba2 NaNb5 O15 (BNN) thin films have been prepared by using metal alkoxides. A homogeneous precursor solution was prepared by the controlled reaction of NaOC2 H5 , Nb(OC2 H5 )5 , and barium metal. The BNN precursor included a molecular-level mixture of NaNb(OC2 H5 )6 and Ba[Nb(OC2 H5 )6 ]2 in ethanol. The alkoxy-derived powder crystallized to a low-temperature phase, and then transformed to orthorhombic BNN (tungsten bronze) at 600°C. BNN precursor films on substrates crystallized to orthorhombic BNN at 800°C via the low-temperature phase. Highly (002) oriented BNN films of tungsten bronze structure were successfully prepared on MgO (100) substrates at 700°C by using BNN underlayer. 相似文献
2.
Shin-ichi Hirano Toshinobu Yogo Ko-ichi Kikuta Toshiyuki Morishita Yasuhiro Ito 《Journal of the American Ceramic Society》1992,75(6):1701-1704
Perovskite potassium tantalate niobate (KTN) powders and thin films were synthesized from a metal alkoxide solution. Homogeneous KTN coating solutions were prepared from KOC2 H5 , Ta(OC2 H5 )5 , and Nb(OC2 H5 )5 in absolute ethanol. The precursor crystallized to pyrochlore at ∼ 650°C, and then to perovskite at ∼ 750°C, depending upon Ta:Nb ratio. H2 O vapor during calcination was found to play a prominent role in the direct and predominant crystallization of perovskite films with preferred orientation. Highly oriented KTN films of perovskite structure were successfully prepared on MgO (100) substrates at 675°C. 相似文献
3.
Toshinobu Yogo Koichi Kikuta Yasuhiro Ito Shin-ichi Hirano 《Journal of the American Ceramic Society》1995,78(8):2175-2179
Highly oriented K(Ta,Nb)O3 (Ta:Nb = 65:35) (KTN) thin films of perovskite structure were synthesized successfully on Pt(100)/MgO(100) substrates from a metal alkoxide solution through reaction control. Homogeneous KTN coating solutions prepared from KOC2 H5 , Ta(OC2 H5 )5 , and Nb(OC2 H5 )5 in ethanol were analyzed by 1 H, 13 C, and 93 Nb NMR spectroscopy. The KTN precursor included a molecular-level mixture of K[M(OC2 H5 )6 ] (M = Ta, Nb) units interacting in ethanol solution. X-ray pole figure measurement showed that perovskite KTN films crystallized on Pt(100)/MgO(100) substrates had not only a (100) orientation but also a three-dimensional regularity of grains. The remanent polarization and coercive field of the KTN film (thickness, 1.0 μm) crystallized at 700°C were 1.5 μC/cm2 and 8.7 kV/cm, respectively, at 225 K. 相似文献
4.
QI-MING YUAN JIA-QI TAN JI-YAO SHEN XUAN-HUI ZHU ZHENG-FANG YANG 《Journal of the American Ceramic Society》1986,69(3):268-269
A high-purity stoichiometric mullite precursor was obtained by hydrolysis of the alkoxides Al(OC3 H7 )3 and Si(OC2 H2 )4 . Fully sintered mullite ceramics can be prepared from sol-gel powders by sintering them at 1600°C for 4 h in air with the addition of 15 to 20 Vol% ZrO2 or 1 to 3 mol% Y2 O3 or both. Introduction of 1 to 3 mol% Y2 O3 aids the retention of tetragonal ZrO2 ; the volume fraction of t -ZrO2 retained increases with increasing Y2 O3 content. The maximum t -ZrO2 retained reaches 34% in a matrix of synthetic mullite with 3 mol% Y2 O3 , but most of this t -ZrO2 does not undergo stress-induced transformation during grinding. 相似文献
5.
A modified sol-gel process has been developed for the production of thin films of PbTiO3 . The new route uses the mixed ligand complex titanium diisopropoxide bis(acetylacetonate), Ti(OC3 H7 )2 (CH3 COCHCOCH3 )2 , in place of titanium tetraisopropoxide, Ti(OC3 H7 )4 . For base-catalyzed conditions, the maximum thickness of crack-free PbTiO3 films after one high-temperature firing cycle is 1 μm. This value represents a twofold increase in thickness over that obtained using existing sol-gel routes based on Ti(OC3 H7 )4 . 相似文献
6.
Yoshikazu Nakamura Tsuneharu Aoi Atsushi Aruga Yoshihisa Watanabe Shigekazu Hirayama Shirou Fujimoto 《Journal of the American Ceramic Society》1995,78(6):1457-1462
A perovskite structure of 0.4Pb(Mg1/3 Nb2/3 )O3 ·0.3Pb(Mg1/2 W1/2 )O3 ·0.3PbTiO3 was prepared from metallo-organic precursors through the solid-state reaction of the mixed gels. Three types of mixed gels were crystallized to obtain PbTiO3 , MgNb2 O6 , and MgWO4 powders. These powders were calcined at 900°C after mixing with a stoichiometric amount of Pb(CH3 COO)2 ·3H2 O. The dielectric constant of the ceramic fired at 900°C was improved by adding an excess of 10 mol% Mg(OC2 H5 )2 , and the ceramic achieved X7T specification of the Electric Industries Association standard. The dielectric loss was reduced by adding an excess of 5 mol% Pb(CH3 COO)2 ·3H2 O. 相似文献
7.
Guangming Li Masayuki Nogami Yoshihiro Abe 《Journal of the American Ceramic Society》1994,77(11):2885-2888
Borosilicate glasses, 5B2 O3 · 95SiO2 (mol%), containing TeO2 and ZnO nominally equivalent to 10 wt% Te and ZnTe were prepared by a solgel method from Si(OC2 H5 )4 , B(OCH3 )3 , H6 TeO6 , and Zn(NO3 )2 . A study by electron spectroscopy for chemical analysis (ESCA) showed that glasses heated at high temperature (450°C) in air contained both Te6+ and Te4+ ions on the surface layer, but that mainly Te4+ ions occurred inside the bulk glass. When solgel-derived borosilicate glasses containing the TeO2 compound were reduced at elevated temperature in a hydrogen atmosphere, Te crystallites ranging in size from 4 to 15 nm were produced at a lower temperature, between 200° and 250°C. The absorption edge moved from the infrared to the visible wavelength region as the particle size decreased to about 4 nm. For glasses containing both TeO2 and ZnO, ZnTe crystallites formed at high temperature—over 300°C—and existed along with the Te phase. 相似文献
8.
Atsushi Aruga Yoshikazu Nakamura Tsuneharu Aoi Yoshihisa Watanabe Shigekazu Hirayama Shirou Fujimoto 《Journal of the American Ceramic Society》1993,76(11):2939-2941
0.4Pb(Mg1/3 Nb2/3 )O3 –0.3Pb(Mg1/2 W1/2 )O3 –0.3PbTiO3 + x MgO ( x = 0 to 0.04) were prepared by a metal alkoxide method. The percent of perovskite phase of the calcined powders increased with increased calcination temperatures. About 89% of perovskite phase was obtained at 1050°C. The dielectric constant of the pellets fired at 1100°C was increased by the addition of 10 wt% excess Mg(OC2 H5 )2 and had a maximum value of 7532 at 1 kHz. 相似文献
9.
Kazuyuki Suzuki Wataru Sakamoto Toshinobu Yogo Shin-ichi Hirano 《Journal of the American Ceramic Society》1999,82(6):1463-1466
K(Ta,Nb)O3 (KTN) thin films have been prepared by the chemical solution deposition method. KTN precursors consisted of a uniform mixture of K[Ta(OC2 H5 )6 ] and K[Nb(OC2 H5 )6 ] with interaction at the molecular level. Perovskite KTN thin films with the desired composition (Ta/Nb = 65/35, 50/50, and 35/65) were synthesized from the precursor solutions by the dip coating method. KTN thin films with (100) preferred orientation were successfully synthesized on MgO(100) and Pt(100)/MgO(100) substrates. X-ray pole figure measurements showed that grains of KTN films had a prominent three-dimensional regularity on MgO(100) and Pt(100)/MgO(100) surfaces. The Curie temperatures of KTN films decreased with increasing Ta/Nb ratio. Typical P-E hysteresis loops were observed for KTN thin films of three compositions on Pt(100)/MgO(100) substrates. The values of remanent polarization ( P r ) of KTN films increased as the Ta/Nb ratio changed from 65/35 to 35/65. 相似文献
10.
Takatoshi Akase Takuya Ryoke Hiromitsu Kozuka 《Journal of the American Ceramic Society》2009,92(9):1951-1958
Titania gel films were prepared from a coating solution with a starting mole ratio of Ti(OC3 H7 i )4 :H2 O:HNO3 :C2 H5 OH=1:1:0.2:30 on Si(100) wafers by spin coating, with and without sol–gel-derived, fired silica, and titania underlayers. In situ measurement was conducted on the in-plane stress in the titania gel films during heating up to 500°C at 5°C/min. Basically, for all the gel films, the in-plane, tensile stress increases once with increasing temperature, and then decreases around the temperature of crystallization. The increase in stress was thought to result from the capillary pressure due to solvent evaporation and from the densification of the coatings. The reduction in stress around the temperature of crystallization was ascribed to the accelerated atomic diffusion in the coatings and to the difference in thermal expansion coefficient between the coatings and the Si wafer. However, when the stress–temperature curves were examined more in detail, differences were found in the variation in stress, depending on the underlayers. Then, the question of how the underlayers could induce the crystallization and relax the strain in the coatings was discussed. 相似文献
11.
Synthesis of Potassium Niobate from Metal Alkoxides 总被引:1,自引:0,他引:1
Preparation of potassium niobate from metal alkoxides was investigated. Potassium-niobium ethoxide, KNb(OC2 H5 )6 , and potassium-niobium propoxide, KNb(OC3 H7 )6 , were synthesized and subsequently hydrolyzed using several water concentrations (0.75 to 6.0 mol of water/(mol of alkoxide)). Rapid precipitation of potassium-deficient particles occurred when higher concentrations of water were used. This resulted in the formation of a multiphase material after calcination, as X-ray diffraction showed the presence of both KNbO3 and potassium-deficient oxide phases(s). Single-phase KNbO3 could be prepared by two methods: (1) hydrolysis of KNb(OC3 H7 )6 /propanol solutions using 1 mol of water (per mole of propoxide) added as a water/propanol solution and (2) hydrolysis of KNb(OC2 H5 )6 /ethanol solutions using 1 mol of water (per mole of ethoxide) added as a water/methanol solution. The latter method provided advantages of low calcination temperature for the formation of single-phase KNbO3 and low weight loss after calcination. 相似文献
12.
Sergey Kucheiko Ji-Won Choi Hyun-Jai Kim Seok-Jin Yoon Hyung-Jin Jung 《Journal of the American Ceramic Society》1997,80(11):2937-2940
The dielectric properties of (Pb1− x Ca x ){(Fe1/2 Nb1/2 )1– y Sn y }O3 solid solutions, where 0.4 lessthan equal tox ≤ 0.6, y = 0.05, 0.1, have been investigated at microwave frequencies. The replacement of Fe3+ /Nb5+ by Sn4+ at the B–site of the perov-skite structure considerably improves the loss quality factor Q and does not remarkably affect the dielectric constant epsilonr and the temperature coefficient of resonant frequency tauf . The tauf value of nearly 0 ppm/°C can be realized for x= 0.55. New high-quality dielectric ceramics having epsilonr of 85.3-89.9,Qf values of 7510-8600 GHz, and τf of 0-9 ppm/°C were obtained at 1150°C for 3 h sintering in air. The influence of the sintering atmosphere on dielectric properties was also investigated. 相似文献
13.
Masayuki Nogami Naoya Hayakawa Naoya Sugioka Yoshihiro Abe 《Journal of the American Ceramic Society》1996,79(5):1257-1261
Samarium ions (Sm2+ ) incorporated into aluminosilicate glasses by a sol-gel process showed persistent spectral hole burning at room temperature. Gels of the system Na2 O-Al2 O3 SiO2 synthesized by the hydrolysis of Si(OC2 H5 )4 , Al(OC4 H9 )3 , CH3 COONa, and SmCl3 ·6H2 O were heated in air at 500°C, then reacted with H2 gas to form Sm2+ ions. Whereas Al3+ ions effectively dispersed the Sm3+ ions in the glass structure, Na+ ions were not effective. The Al2 O3 -SiO2 glasses proved appropriate for reacting the Sm3+ ions with H2 gas and exhibited the intense photoluminescence of Sm2+ ions. The reaction of Sm3+ ions with H2 in the Al2 O2 -SiO2 glasses was determined by first-order kinetics, and the activation energy equaled 95 kJ/mol. At 800°C, the maximum photoluminescence of the Sm2+ ions was achieved within 20 min. 相似文献
14.
Jin-Ho Lee Masatomo Yashima Masato Kakihana Masahiro Yoshimura 《Journal of the American Ceramic Society》1998,81(4):894-900
The phase equilibria in the Y2 O3 -Nb2 O5 system have been studied at temperatures of 1500° and 1700°C in the compositional region of 0-50 mol% Nb2 O5 . The solubility limits of the C-type Y2 O3 cubic phase and the YNbO4 monoclinic phase are 2.5 (±1.0) mol% Nb2 O5 and 0.2 (±0.4) mol% Y2 O3 , respectively, at 1700°C. The fluorite (F) single phase exists in the region of 20.1-27.7 mol% Nb2 O5 at 1700°C, and in the region of 21.1-27.0 mol% Nb2 O5 at 1500°C, respectively. Conductivity of the Y2 O3 - x mol% Nb2 O5 system increases as the value of x increases, to a maximum at x = 20 in the compositional region of 0 ≤ x ≤ 20, as a result of the increase in the fraction of F phase. In the F single-phase region, the conductivity decreases in the region of 20-25 mol% Nb2 O5 , because of the decrease in the content of oxygen vacancies, whereas the conductivity at x = 27 is larger than that at x = 25. The conductivity decreases as the value of x increases in the region of 27.5 ≤ x ≤ 50, because of the decrease in the fraction of F. The 20 mol% Nb2 O5 sample exhibits the highest conductivity and a very wide range of ionic domain, at least up to log p O 2 =−20 (where p O 2 is given in units of atm), which indicates practical usefulness as an ionic conductor. 相似文献
15.
Masayuki Nogami Yoichi Goto Yasushi Tsurita Toshihiro Kasuga 《Journal of the American Ceramic Society》2001,84(11):2553-2556
The effect of phosphorus ions on the proton conductivity was examined for the sol–gel-derived glasses. The porous glasses were prepared through hydrolysis of PO(OCH3 )3 and Si(OC2 H5 )4 , in which the phosphorus ions consisted of the POH bonds and were dissolved into the silica matrix without any P-O-Si bond. The electrical conductivity increased in a humid atmosphere and reached ∼30 mS/cm at 50°C under 70% RH. High conductivity is achieved by both the POH bonds and the molecular water bonded to the POH bonds. The conductivity increased with a change in humidity from 40% to 80% RH. The phosphorus ions were selectively dissolved in water, resulting in a lower conductivity. 相似文献
16.
Toshiaki Yamaguchi Wataru Sakamoto Toshinobu Yogo Shin-ichi Hirano 《Journal of the American Ceramic Society》2002,85(4):909-914
The effects of the substitution of transition-metal ions and/or reductant gases on the catalytic properties of barium hexaaluminogallate were investigated. Transition-metal-substituted hexaaluminogallates (BaM(Al,Ga)11 O19 , M = transition metal, Al/Ga = 9/3) were synthesized from aqueous metal nitrates and ammonium carbonate by the coprecipitation followed by crystallization at 1100°C. The direct NO x reduction was observed over BaM(Al,Ga)11 O19 to be around 10%. The NO x removal activity of BaM(Al,Ga)11 O19 powders was improved by addition of C3 H6 as a reductant gas. Co-, Ni- and Cu-substituted BaM(Al,Ga)11 O19 catalysts exhibited about 40% NO x reduction with C3 H6 in excess oxygen at a high space velocity of 10 000 h−1 . The NO x reduction on Mn- and Fe-substituted BaM(Al,Ga)11 O19 catalysts was less than 10% even in the presence of C3 H6 . The temperature of the effective NO x reduction on BaM(Al,Ga)11 O19 catalysts could be adjusted from 350° to 500°C by the selection of the transition-metal substitution in the catalysts. The catalysts hold high activities for NO x reduction even at 500°C in water vapor produced in the combustion system of reductant gases. 相似文献
17.
Masayuki Nogami Katsumi Nagaska Etsuro Kato 《Journal of the American Ceramic Society》1990,73(7):2097-2099
The sol–gel process has been applied successfully to the preparation of small-particle-size CdS-doped silica glasses with a significant quantum size effect. Gels prepared through the hydrolysis of a complex solution of Si(OC2 H5 )4 and Cd(CH3 COO)2 ·2H2 O were heated at 500°C, then reacted with H2 S gas to form fine, hexagonal, CdS-microcrystal-doped glasses. The optical absorption edge is blue shifted by ∼0.4 eV compared with the bulk absorption value of CdS crystal. This result is interpreted in terms of a quantum-confinement effect of small crystal size. 相似文献
18.
The crystals of Ca2 (Al x Fe1− x )2 O5 with 0 ≤ x ≤ 0.4 were examined using powder XRD at temperatures between 25° and 1000°C. The Pcmn to Ibm 2 phase transition was readily detected by the disappearance of the 131 and 151 reflections ( h + k + l odd). Thus, the phase relationship has been determined as combined functions of the temperature and x -value. At 25°C, the space group changed from Pcmn (0 ≤ x ≤ 0.23) to Ibm 2 (0.24 ≤ x ≤ 0.40) across x = 0.235. With increased x -value, the cell dimensions of both phases steadily decreased, showing the nearly complete continuity at that phase boundary. For the crystal with x = 0 (Ca2 Fe2 O5 ), the cell dimensions steadily increased during heating to 685°C, at which temperature the phase transition occurred. There was a slight discontinuous decrease in cell dimensions just after the transition. Subsequent heating to 1000°C of the Ibm 2 phase led to a steady thermal expansion along the b -axis and c -axis, while a slight contraction occurred along the a -axis up to 800°C. 相似文献
19.
Masayuki Nogami Yi-Qing Zhu Yoshihide Tohyama Katsumi Nagasaka Takashi Tokizaki Arao Nakamura 《Journal of the American Ceramic Society》1991,74(1):238-240
The sol–gel process has been applied successfully to the preparation of small-sized CuCl-doped silica glass with a significant quantum-sized effect. Gel synthesized by the hydrolysis of a complex solution of Si(OC2 H5 )4 and CuCl with an HCl catalyst is heated to 900°C to form fine, cubic CuCl crystals. Above 700°C, absorption peaks observed at ∼370 and ∼380 nm are attributed to the excitation of confined Z1,2 and Z3 excitons, respectively, in the CuCl microcrystals. As the size of the CuCl crystals decreases, exciton energy shifts to the higher-energy side. The resonant third-order nonlinear susceptibility at 77 K is 1.1 × 10−8 esu, which originates from the enhancement by the quantum-sized effect of the exciton. 相似文献
20.
Kanichi Kamiya Tomoaki Nishijima Katsuhisa Tanaka 《Journal of the American Ceramic Society》1990,73(9):2750-2752
Dip-coated sol–gel-derived TiO2 films on an alumina substrate were converted to nonstoichiometric titanium nitride (TiN x ( x ≦ 1)) films by heating at approxmately 1000°C in NH3 gas. TiO2 films made from TiO2 sols prepared from Ti(O– i -C3 H7 )4 and stabilized by diethanolamine were more easily nitrided than those from sols containing HCl as a deflocculant reagent. This appears to be a result of the more porous structure of the former films. 相似文献