共查询到20条相似文献,搜索用时 15 毫秒
1.
Michael Rozumek Peter Majewski Linda Sauter Fritz Aldinger 《Journal of the American Ceramic Society》2003,86(11):1940-1946
Phase stability studies were performed within the quasi-ternary system LaGaO3 -SrGaO2.5 -"LaMgO2.5 ". Emphasis was cast on the temperature dependence of the homogeneity region of La1− x Sr x Ga1− y Mg y O3−δ perovskite solid solutions. Isothermal sections were determined at 1100°, 1250°, 1400°, and 1500°C in a static air atmosphere. The single-phase homogeneity region was found to considerably diminish with decreasing temperature, indicating a reduction of the solid solubility of Sr and Mg, and below 1100°C the doped perovskite becomes unstable. Consequently, the cubic perovskite phase was found to exist only at elevated temperatures and for high Sr and Mg amounts. Sample preparation was performed by the mixed-oxide process as well as by a modified combustion synthesis. 相似文献
2.
The effect of the addition of V2 O5 on the structure, sintering and dielectric properties of M -phase (Li1+ x − y Nb1− x −3 y Ti x +4 y )O3 ceramics has been investigated. Homogeneous substitution of V5+ for Nb5+ was obtained in LiNb0.6(1− x ) V0.6 x Ti0.5 O3 for x ≤ 0.02. The addition of V2 O5 led to a large reduction in the sintering temperature and samples with x = 0.02 could be fully densified at 900°C. The substitution of vanadia had a relatively minor adverse effect on the microwave dielectric properties of the M -phase system and the x = 0.02 ceramics had [alt epsilon]r = 66, Q × f = 3800 at 5.6 GHz, and τf = 11 ppm/°C. Preliminary investigations suggest that silver metallization does not diffuse into the V2 O5 -doped M -phase ceramics at 900°C, making these materials potential candidates for low-temperature cofired ceramic (LTCC) applications. 相似文献
3.
Sergey Kucheiko Dong-Hun Yeo Ji-Won Choi Seok-Jin Yoon Hyun-Jai Kim 《Journal of the American Ceramic Society》2002,85(5):1327-1329
The microwave dielectric properties of CaTi1− x (Al1/2 Nb1/2 ) x O3 solid solutions (0.3 ≤ x ≤ 0.7) have been investigated. The sintered samples had perovskite structures similar to CaTiO3 . The substitution of Ti4+ by Al3+ /Nb5+ improved the quality factor Q of the sintered specimens. A small addition of Li3 NbO4 (about 1 wt%) was found to be very effective for lowering sintering temperature of ceramics from 1450–1500° to 1300°C. The composition with x = 0.5 sintered at 1300°C for 5 h revealed excellent dielectric properties, namely, a dielectric constant (ɛr ) of 48, a Q × f value of 32 100 GHz, and a temperature coefficient of the resonant frequency (τf ) of −2 ppm/K. Li3 NbO4 as a sintering additive had no harmful influence on τf of ceramics. 相似文献
4.
Tianmin He Qiang He Li Pei Yuan Ji Jiang Liu 《Journal of the American Ceramic Society》2006,89(8):2664-2667
A colloidal deposition without any binder was developed to prepare a dense La0.8 Sr0.2 Ga0.85 Mg0.15 O3−δ (LSGM) film on porous NiO/YSZ substrates, using an incompletely crystallized LSGM powder as starting material. Both the dense LSGM film with a thickness of 15 μm and the required phase composition of the LSGM were achieved simultaneously by sintering at 1400°C for 6 h. The conductivity of the supported LSGM film attained 0.102 S/cm at 800°C, which was comparable with those of the self-supported LSGM films. The maximum power density of the LSGM film cell was 480 at 800°C and 614 mW/cm2 at 850°C, respectively. 相似文献
5.
Hyo Tae Kim Thomas Shrout Clive Randall Michael Lanagan 《Journal of the American Ceramic Society》2002,85(11):2738-2744
The sintering behavior and dielectric properties of perovskite Ag(Nb1− x Ta x )O3 (0 < x < 1) solid solutions and two-phase composite assemblages were explored. A small amount of CuO (1 wt%) was used for liquid-phase sintering and led to high densification at temperatures <950°C. The temperature coefficient of capacitance, TCC, was adjusted by varying the Nb:Ta ratio within the solid-solution series and by creating composite microstructures. Two-phase assemblages consisting of Ag(Nb3/4 Ta1/4 )O3 and Ag(Nb1/4 Ta3/4 )O3 were synthesized to achieve a temperature-stable dielectric material for high-frequency applications. The composite dielectric with CuO addition had an average dielectric constant of 390 and a Q × f factor of 410 GHz at 2 GHz, with a stable TCC (0 to −180 ppm/°C) in the temperature range from −20° to +60°C. In addition, process compatibility with a silver conductor was confirmed by high-frequency ring-resonator measurements and microstructural characterization. The Ag(Nb1− x Ta x )O3 solid solutions and composites are promising candidates as embedded capacitors for radio-frequency/microwave applications. 相似文献
6.
Hyun-Cheol Song Kyung-Hoon Cho Hwi-Yeol Park Cheol-Woo Ahn Sahn Nahm Kenji Uchino Seung-Ho Park Hyeung-Gyu Lee 《Journal of the American Ceramic Society》2007,90(6):1812-1816
(1− x )(Na0.5 K0.5 )NbO3 – x LiNbO3 [(1− x )NKN– x LN] ceramics were produced by the conventional solid-state sintering method, and their microstructure and piezoelectric properties were investigated. The formation of the liquid phase and K6 Li4 Nb10 O30 second phase that were observed in the (1− x )NKN– x LN ceramics was explained by the evaporation of Na2 O during the sintering. A morphotropic phase boundary (MPB) was observed in the specimens with 0.05< x <0.08. Promising piezoelectric properties were obtained for the specimens with x =0.07. Therefore, the piezoelectric properties of this 0.93NKN–0.07LN ceramic were further investigated and were found to be influenced by their relative density and grain size. In particular, grain size considerably affected the d 33 value. Two-step sintering was conducted at different temperatures to increase the grain size. Piezoelectric properties of d 33 =240 (pC/N) and k p =0.35 were obtained for the 0.93NKN–0.07LN ceramics sintered at 1030°C and subsequently annealed at 1050°C. 相似文献
7.
Ching-Fang Tseng Cheng-Liang Huang Cheng-Hsing Hsu 《Journal of the American Ceramic Society》2007,90(5):1619-1622
The microwave dielectric properties and the microstructures of Nd(Co1/2 Ti1/2 )O3 (NCT) ceramics using starting powders of Nd2 O3 , CoO, and TiO2 prepared by the conventional solid-state route have been researched. The dielectric constant values (ɛr ) saturated at 24.8–27. Quality factor ( Q × f ) values of 37 900–140 000 (at 9 GHz) and the measured τf values ranging from −45 to −48 ppm/°C can be obtained when the sintering temperatures are in the range of 1410°–1500°C. The ɛr value of 27, the Q × f value of 140 000 (at 9 GHz) and the τf value of −46 ppm/°C were obtained for NCT ceramics sintered at 1440°C for 4 h. For applications of high selective microwave ceramic resonator, filter, and antenna, NCT is proposed as a suitable material candidate. 相似文献
8.
Fabrication of Low-Porosity Indium Tin Oxide Ceramics in Air from Hydrothermally Prepared Powder 总被引:1,自引:0,他引:1
Chandana P. Udawatte Kazumichi Yanagisawa 《Journal of the American Ceramic Society》2001,84(1):251-253
Compositionally homogeneous indium tin oxide (ITO) ceramics with low porosity were obtained successfully by sintering hydrothermally prepared powders. The fabrication technique began with the preparation of microcrystalline, homogeneously tin-doped (5 wt%) indium oxyhydroxide powder, under hydrothermal conditions. Low-temperature (∼500°C) calcination of the hydrothermally derived powder led to the formation of a substitutional-vacancy-type solid solution of In2 Sn1− x O5− y , and further heating of this phase at temperatures of >1000°C resulted in the formation of the tin-doped indium oxide phase, which had the C -type rare-earth-oxide structure. The sintering of uniformly packed, calcined powder compacts at 1450°C for 3 h in air resulted in low-porosity (∼0.7%) ITO ceramics. 相似文献
9.
Charles N. Pieczulewski Kelly S. Kirkpatrick Thomas O. Mason 《Journal of the American Ceramic Society》1990,73(7):2141-2143
The phase relations involving the 24 K n -type Nd2- x Ce x CuO4 superconductor were investigated at 1000°C in air. The terminal solid solubility was confirmed to be x = 0.2. This solid solution is the only ternary phase in the Nd2 O3 –CeO2 –CuO diagram. A binary (1 − y )CeO2 – y NdO1.5 solid solution exists out to y = 0.4. Phase diagrams for NdO1.5 –CeO2 –CuO (1000°C) and NdO1.5 –CeO2 (900° to 1500°C) are presented. 相似文献
10.
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
11.
Improvement of Mechanical Properties and Corrosion Resistance of Porous β-SiAlON Ceramics by Low Y2 O3 Additions 总被引:2,自引:1,他引:1
Jian-Feng Yang Guo-Jun Zhang Ji-Hong She Tatsuki Ohji Shuzo Kanzaki 《Journal of the American Ceramic Society》2004,87(9):1714-1719
Addition of Y2 O3 as a sintering additive to porous β-SiAlON (Si6− z Al z O z N8− z , z = 0.5) ceramics has been investigated for improved mechanical properties. Porous SiAlON ceramics with 0.05–0.15 wt% (500–1500 wppm) Y2 O3 were fabricated by pressureless sintering at temperatures of 1700°, 1800°, and 1850°C. The densification, microstructure, and mechanical properties were compared with those of Y2 O3 -free ceramics of the same chemical composition. Although this level of Y2 O3 addition did not change the phase formation and grain size, the grain bonding appeared to be promoted, and the densification to be enhanced. There was a significant increase in the flexural strength of the SiAlON ceramics relative to the Y2 O3 -free counterpart. After exposure in 1 M hydrochloric acid solution at 70°C for 120 h, no remarkable weight loss and degradation of the mechanical properties (flexural and compression strength) was observed, which was attributed to the limited grain boundary phase, and with the minor Y2 O3 addition the supposed formation of Y-α-SiAlON. 相似文献
12.
Lead-free (Na0.52 K0.48− x )(Nb1− x − y Sb y )O3 - x LiTaO3 (NKNS–LT) piezoelectric ceramics have been fabricated by ordinary sintering. A special attention was paid to the composition design through which the dielectric and piezoelectric properties of the (Li, Ta, Sb) modified NKN systems were significantly promoted. A property spectrum was generated with a particular discussion on the relationship between the Sb content, the LT content, the polymorphic phase transition, and the electrical properties and their temperature stability. Excellent and tunable electrical properties of d 33 =242–400 pC/N, k p =36%–54%, , and T c =230°–430°C demonstrate a tremendous potential of the compositions studied for device applications. 相似文献
13.
Noboru Tohge Satoshi Takahashi Tsutomu Minami 《Journal of the American Ceramic Society》1991,74(1):67-71
Ferroelectric films, PbZr x Ti1− x O3 ( x = 0 to 0.6), have been prepared from corresponding metal alkoxides partially stabilized with acetylacetone through the sol-gel process. The films dip-coated in an ambient atmosphere were heat-treated at 400°C for decomposition of residual organics and then at temperatures between 500° and 700°C for crystallization of the films. The perovskite phase precipitated at temperatures above 560°C, accompanied by an increase in dielectric constant. The dielectric constant of the films, which was comparable with that of sintered bodies, showed a maximum (∼620) at around x = 0.52 in PbZr x Ti1− x O3 . These films showed D – E hysteresis, with slightly higher values of coercive field, compared with those of sintered bodies. 相似文献
14.
Sintering behavior, phase evolution, and microwave dielectric properties of Bi(Sb1− x Ta x )O4 ceramics (0.05≤ x ≤0.60) were studied and their relationships were discussed in detail. Phase studies revealed that a pure monoclinic phase could be formed when x ≤0.20 and a pure orthorhombic phase could be obtained when x ≥0.50. As the x value increased from 0.05 to 0.60, the densified temperature of Bi(Sb1− x Ta x )O4 ceramics decreased from 1050° to about 960°C whereas the density increased from 8.07 to 8.41 g/cm3 . The microwave dielectric constant increased from 20.5 to 34 whereas the Q × f value decreased from 60 000 to 29 000 GHz. In the monoclinic phase region, the temperature coefficients of resonant frequency shifted linearly from −58 to −45 ppm/°C as the x value increased from 0.05 to 0.2 and then remained constant at about −12 ppm/°C when x ≥0.40. The Bi(Sb1− x Ta x )O4 ceramics are promising for application of low-temperature cofired ceramics technology. 相似文献
15.
Chang Wei Zheng Shu Ya Wu Xiang Ming Chen Kai Xin Song 《Journal of the American Ceramic Society》2007,90(5):1483-1486
MgAl2 O4 microwave dielectric ceramics were modified by Zn substitution for Mg, and their dielectric characteristics were evaluated, along with their structures. Dense (Mg1− x Zn x )Al2 O4 ceramics were obtained by sintering at 1550°–1650°C in air for 3 h, and the (Mg1− x Zn x )Al2 O4 solid solution was determined in the entire composition range. With Zn substitution for Mg, the dielectric constant ɛ of MgAl2 O4 just varied from 7.90 to 8.56, while the Q × f value had significantly improved up to a maximal value of 106 000 GHz at x =1.0. Moreover, the τf of MgAl2 O4 ceramics had declined from −73 to −63 ppm/°C. 相似文献
16.
Ni Qin Marjeta Maek Krmanc Danilo Suvorov 《Journal of the American Ceramic Society》2008,91(8):2593-2600
K x Ba1− x Ga2− x Ge2+ x O8 (0.6≤ x ≤1) polycrystalline ceramics are potential materials for glass-free low-temperature cofired ceramics (LTCC) substrates. We have made a comprehensive study of the kinetics of the monoclinic-to-monoclinic P 21 / a ⇔ C 2/ m phase transition. The low-temperature-stable P 21 / a phase with a high Q × f value was synthesized using a subsolidus method and was well sintered at the LTCC temperature with a H3 BO3 additive. A good combination of low sintering temperature (910°–920°C), high Q × f values (96 700–104 500 GHz), low permittivities (5.6–6.0), and a small temperature coefficient of resonant frequency (∼−20 ppm/°C) was obtained for ceramics with x =0.67 and 0.9 and with 0.1 wt% of H3 BO3 . 相似文献
17.
Nahum Masó Hector Beltrán Raquel Muñoz Beatriz Julián Juan B. Carda Purificación Escribano Eloisa Cordoncillo 《Journal of the American Ceramic Society》2003,86(3):425-430
The development of red pigments is of great interest to the ceramic industry. Pr(IV) stabilization in a CeO2 matrix yields materials with a red color. In this study, the traditional ceramic method involving solid-state reaction was used to prepare pigments in the system Ce1− x Pr x O2−δ (0.005 ≤ x ≤ 0.1) from mixtures of rare-earth oxides. The chemical stability of these pigments was then determined in some industrial glazes. The glazing tests indicate that the powder samples calcined at 1200° and1300°C are unstable, whereas those calcined at 1400° and 1500°C are stable. These findings are related to the nonformation of a solid solution, to which the pigmenting power is attributed, in calcinations at temperatures below 1400°C. 相似文献
18.
Qun Zeng Wei Li Jian-lin Shi Xian-lin Dong Jing-kun Guo 《Journal of the American Ceramic Society》2008,91(2):644-647
A group of new y M-phase/(1− y ) Li2+ x Ti1−4 x Nb3 x O3 composite ceramics with adjustable permittivities for low-temperature co-fired ceramic applications was initially investigated in the study. The 0.5 M-phase/0.5 Li2+ x Ti1−4 x Nb3 x O3 ( x =0.01, 0.02, 0.04, 0.06, 0.081) composite ceramics were first investigated to find the appropriate "Li2 TiO3 ss" composition ( x value). The best dielectric properties of ɛr =40.1, Q × f values up to 9318 GHz, τf =25 ppm/°C, were obtained for the ceramics composites at x =0.02. Based on the good dielectric properties, the suitable "Li2 TiO3 ss" composition with x =0.02 was mixed with the Li1.0 Nb0.6 Ti0.5 O3 powder as the ratio of y "M-phase"/(1− y ) "Li2 TiO3 ss" ( y =0.2, 0.4, 0.5, 0.6, 0.8). By adjusting the y values, the group of composite ceramics could exhibit largely are adjustable permittivities varying from ∼20 to ∼60, while Q × f and τf values relatively good. Nevertheless, in this study, because there are interactions between the M-phase and Li2 TiO3 ss during sintering process, their microwave dielectric properties could not be predicted precisely by the empirical model. 相似文献
19.
Gui-hua Peng Min Liang Zhen-hua Liang Qing-yu Li Wen-lan Li Qian Liu 《Journal of the American Ceramic Society》2009,92(9):2122-2124
Silicon nitride ceramics were prepared by spark plasma sintering (SPS) at temperatures of 1450°–1600°C for 3–12 min, using α-Si3 N4 powders as raw materials and MgSiN2 as sintering additives. Almost full density of the sample was achieved after sintering at 1450°C for 6 min, while there was about 80 wt%α-Si3 N4 phase left in the sintered material. α-Si3 N4 was completely transformed to β-Si3 N4 after sintering at 1500°C for 12 min. The thermal conductivity of sintered materials increased with increasing sintering temperature or holding time. Thermal conductivity of 100 W·(m·K)−1 was achieved after sintering at 1600°C for 12 min. The results imply that SPS is an effective and fast method to fabricate β-Si3 N4 ceramics with high thermal conductivity when appropriate additives are used. 相似文献
20.
Jiagang Wu Ting Peng Yuanyu Wang Dingquan Xiao Jumu Zhu Yong Jin Jianguo Zhu Ping Yu Lang Wu Yihang Jiang 《Journal of the American Ceramic Society》2008,91(1):319-321
(1− x )(K0.48 Na0.52 )(Nb0.95 Ta0.05 )O3 – x LiSbO3 [(1− x )KNNT− x LS] lead-free piezoelectric ceramics were prepared by the conventional solid-state sintering method. A morphotropic phase boundary (MPB) between orthorhombic and tetragonal phases was identified in the composition range of 0.03< x <0.05. The ceramics near the MPB exhibit a strong compositional dependence and enhanced electrical properties. The (1− x )KNNT– x LS ( x =0.04) ceramics exhibit good electrical properties ( d 33 =250 pC/N, k p =45.1%, k t =46.3%, T c =348°C, T o − t =74°C, P r =25.9 μC/cm2 , E c =10.7 kV/cm, ɛr ∼1352, tan δ∼3%). These results show that (1− x )KNNT– x LS ceramic is a promising lead-free piezoelectric material. 相似文献