共查询到20条相似文献,搜索用时 15 毫秒
1.
Liying Chen Shunhua Wu Shuang Wang Guoqing Wang 《Journal of Materials Science: Materials in Electronics》2008,19(5):463-465
The microwave dielectric properties of BaO–TiO2–ZnO (BTZ) system ceramics were studied as a function of the amount of Nb2O5 dopant. With the addition of 0–0.025 mol% Nb2O5, the substitution of Ti4+ ions with Nb5+ ions decreased the sintering temperature and increased the dielectric constant εr and quality factor Q of the system due to the similar atomic radius of Nb5+ and Ti4+ ions. When the amount of Nb5+ increased further (>0.025 mol%), Q was decreased by increasing the titanium vacancies. When the system doped with 0.025 mol%
Nb2O5 was sintered at 1160 °C for 6 h, the εr, Qf0, and the temperature coefficient of resonant frequency (τf) were 36.7, 41,000 GHz, and −5.0 ppm/°C, respectively, at 5 GHz. 相似文献
2.
X. M. Chen Y. Suzuki N. Sato 《Journal of Materials Science: Materials in Electronics》1995,6(1):10-16
The microstructures and the microwave dielectric characteristics of BaO·Nd2O3·5TiO2 ceramics were determined as a function of the sintering conditions. The ceramics were confirmed to have a ternary orthorhombic major phase with minor amounts of Nd2Ti2O7 and TiO2, and nearly equiaxed fine structures and homogeneous columnar structures were obtained at sintering temperatures of 1340 C and 1370 C, respectively, while discontinuous and excess grain growth were observed at sintering temperatures 1350–1360 C and 1380 C, due to the formation of a liquid phase. The desired value of Qf was achieved in ceramics with fine-grained and/or homogeneous microstructures, and the discontinuous and excess grain growth was found to be seriously harmful to the dielectric properties. 相似文献
3.
Nakamori Ryogo Kawano Naoki Nakauchi Daisuke Kato Takumi Fukushima Hiroyuki Takebuchi Yuma Shinozaki Kenji Yanagida Takayuki 《Journal of Materials Science: Materials in Electronics》2022,33(26):20470-20478
Journal of Materials Science: Materials in Electronics - 1Eu2O3–3BaO–20Nb2O5–76TeO2 glass and the corresponding glass-ceramics were synthesized with the aim to investigate the... 相似文献
4.
Chunchun Li Xiaoyong Wei Haixue Yan Michael J. Reece Hongjun Ye 《Journal of Materials Science: Materials in Electronics》2013,24(6):1947-1954
A series of ceramics with a general formula Ca1+xLa4?xNbxTi5?xO17 (0 ≤ x ≤ 4) were fabricated using the solid-state ceramic route. The phase, microstructure, and microwave dielectric properties varied distinctly with composition or the value of x. X-ray diffraction results showed that the two end member phases, CaLa4Ti5O17 and Ca5Nb4TiO17, crystallized into single phases with orthorhombic and monoclinic crystal structure, respectively. For intermediate compounds with x = 1, 2, and 3, mixture phases CaLa4Ti5O17 and Ca5Nb4TiO17 coexisted and a trace amount of second phase was detected. The ceramics showed high ε r in the range of 45–52, relatively high quality factors with Q × f in the range of 9,870–15,680 GHz and τ f value in the range between ?38 and ?126.4 ppm/°C. τ f of CaLa4Ti5O17 can be tuned to a near-zero value by addition of suitable amount of TiO2. 相似文献
5.
Yihe Zhang Li Yu Qingsong Su Hong Zheng Haitao Huang H. L. W. Chan 《Journal of Materials Science》2012,47(4):1958-1963
A sol–gel process was used to prepare polyimide–silica hybrid films from the fluorinated polyimide precursors (6FDA-ODA) and
tetraethylorthosilicate (TEOS) in N,N-dimethyl acetamide. The hybrid film was then treated with hydrofluoric acid to remove the dispersed silica particles, leaving
inside the film pores with diameters ranged from 80 nm to 1 μm, which depended on the size of the silica particles. The chemical
structures and morphology of the hybrid and porous films were characterized by Fourier transform infrared spectroscopy and
scanning electron microscopy, respectively. The synthesized porous fluorinated polyimide films show low relative dielectric
permittivity of 1.9, rendering them promising for microelectronic packaging materials. 相似文献
6.
7.
Phase relations in the Na2O–Al2O3–Nb2O5and CaO–Al2O3–Nb2O5systems were studied. The Na2O system was found to contain neither ternary compounds nor niobate–aluminate solid solutions. In the CaO system, a ternary compound of composition 4CaO · Al2O3·Nb2O5was identified (cubic structure, a= 7.628 Å, Z= 2, meas= x= 4.43 g/cm3). 相似文献
8.
Huanfu Zhou Hong Wang Xiaoyan Ding Xi Yao 《Journal of Materials Science: Materials in Electronics》2009,20(1):39-43
A new Li2O–Nb2O5–TiO2 (LNT) ceramic with the Li2O:Nb2O5:TiO2 mole ratio of 3:1:3 has been investigated. The compound is composed of two phases, the Li2TiO3 and “M-phase” solid solution phase. The microwave dielectric ceramic has low sintering temperature (∼1100 °C) and good microwave
dielectric properties of a relatively high permittivity (∼51), high Q × f value up to 8700, and small temperature coefficient (∼37 ppm/°C). The low-amount doping of 0.83Li2O–0.17V2O5 (LV) can effectively lower the sintering temperature from 1100 to 900 °C and induce no obvious degradation of the microwave
dielectric properties. Typically, the 1 wt.% LV-doped ceramic sintered at 900 °C has better microwave dielectric properties
of εr = 51.3, Q × f = 7235 GHz, τ
f
= 22 ppm/°C, which suggests that the ceramics can be applied in microwave LTCC devices. 相似文献
9.
Zupei Yang Hongmei Ren Xiaolian Chao Pengfei Liang 《Materials Research Bulletin》2012,47(5):1273-1277
The phase structure, microstructure and dielectric properties of Na0.5Bi0.5?xLaxCu3Ti4O12 (NBLCTO) ceramics were investigated. La3+ substitution had a great influence on the phase structure and dielectric properties. The results showed that the pure phase could be more easily obtained when substituting La3+ for Bi3+. Under the same processing condition (970 °C for 7.5 h) and measuring condition (10 kHz around room temperature), NBLCTO ceramics with x = 0.10 possessed the highest permittivity (1.02 × 104) and lowest dielectric loss (0.022). The obtained NBLCTO ceramics with x = 0.10 also had good frequency stability and good temperature stability (?1.87% to +3.27%) from ?60 °C to 120 °C at both 1 and 10 kHz. Complex impedance results revealed that the grain resistance Rg was 7.18 Ω cm and the grain boundary resistance Rgb was 1.19 × 106 Ω cm. 相似文献
10.
Phase relations in the systems Al2TiO5–Fe2O3, Al2TiO5–Cr2O3, and Al2O3–TiO2–Fe2O3 are investigated, and the composition ranges of pseudobrookite Al2
– 2x
M2x
TiO5 (M = Fe, Cr) solid solutions are determined. 相似文献
11.
12.
Xingyu Chen Weijun Zhang Shuxin Bai 《Journal of Materials Science: Materials in Electronics》2013,24(1):224-229
The effects of Bi4B2O9 addition on the sintering temperature, phase transition and microwave dielectric properties of BaO–Nd2O3–4TiO2 (BNT) ceramics have been investigated. With 10 wt% Bi4B2O9 addition, the sintering temperature of the BNT ceramics can be lowered down to about 1,150 °C. The secondary phase was observed at the level of 15 wt% Bi4B2O9 addition. The Bi4B2O9 addition can significantly affects the microwave dielectric properties. The Q × f 0 value is a function of the sintering temperature and the Bi4B2O9 content. For the samples sintered at 1,150 °C, Q × f 0 value varies from 6,300 to 3,300 GHz as the Bi4B2O9 addition increases from 5 to 20 wt%. The addition of Bi4B2O9 does not induce much degradation in εr but modified the τf value to near zero. Typically, When 10 wt% Bi4B2O9 is added, the τf of the ceramics could be tuned to a near-zero value (~1.2 ppm/°C), a substantial εr (~86) and Q × f 0 (~4,670 GHz) could also be achieved simultaneously. The Bi4B2O9 is an efficient sintering additive to decrease the sintering temperature and tune the τf value of the microwave dielectric materials for the practical microwave applications. 相似文献
13.
Choon-W. Nahm 《Journal of Materials Science: Materials in Electronics》2012,23(2):457-463
The effect of sintering process on microstructure, electrical properties, and ageing behavior of ZnO–V2O5–MnO2–Nb2O5 (ZVMN) varistor ceramics was investigated at 875–950 °C. The sintered density decreased from 5.52 to 5.44 g/cm3 and the average grain size increased from 4.4 to 9.6 μm with the increase of sintering temperature. The breakdown field (E1 mA) decreased from 6991 to 943 V/cm with the increase of sintering temperature. The ZVMN varistor ceramics sintered at 900 °C
led to surprisingly high nonlinear coefficient (α = 50). The donor concentration (Nd) increased from 3.33 × 1017 cm−3 to 7.64 × 1017 cm−3 with the increase of sintering temperature and the barrier height (Φb) exhibited the maximum value (1.07 eV) at 900 °C. Concerning stability, the varistors sintered at 925 °C exhibited the most
stable accelerated ageing characteristics, with %ΔE1 mA = 1.5% and %Δα = 13.3% for DC accelerated ageing stress of 0.85 E1 mA/85 °C/24 h. 相似文献
14.
Ceramics of solid solution compositions in the system BaTi1–x–ySnxZryO3 have been fabricated using conventional mixed oxide processing routes. Samples with y = 0 or 0.01 exhibited maximum relative permittivities,
r
max
of ~ 65000 and ~ 62000 respectively. The Curie peaks became broader and
r
max
decreased with increasing zirconium substitutions. The Curie temperature decreased linearly from 35°C for y = 0 to –40°C for y = 0.11: for the latter,
r
max
was equal to ~ 20000. The results are interpreted on the basis of microstructural features and on the degree of compositional inhomogeneity in the system. 相似文献
15.
Ricardo Guido Follador Neto Eder Carlos Ferreira de Souza André Vitor Chaves de Andrade Sandra Regina Masetto Antunes Augusto Celso Antunes 《Journal of Materials Science: Materials in Electronics》2013,24(3):938-944
This work investigated the influence of Nb2O5 dopant on the varistor behavior of the ternary system (99.95 ? x)%TiO2, 0.05 %Cr2O3, x%Nb2O5, where x = 0.10; 0.15; 0.20; 0.25 % in mol. The processing was carried out using the conventional oxide mixture method. The initial oxides were homogenized in alcoholic media in a ball mill, for 3 h, dried in oven and isostatically pressed at 210 MPa and sintered at 1,400 °C for 2 h in air atmosphere and cooled at 5 °C/min cooling rate, resulting in pellets with high densification. Electrical measurements in continuous current at different temperatures revealed that for the lowest Nb2O5 concentration the breakdown electric field, EB = 4.41 V/cm and non-linear coefficient, α = 4.6 were obtained, and for the highest Nb2O5 concentration the breakdown electric field, EB = 9.71 V/cm and non-linear coefficient, α = 15.3 were obtained. These low values in the breakdown electric field enable these varistor systems to be used in protection systems for low-voltage energy grids. Changes in the potential barrier present in the grain–grain boundaries could also be observed, in which the height increased and the width decreased with the increase in the dopant concentration. However, for x = 0.25 % in mol Nb2O5, a significant reduction in the potential barrier height and the voltage per barrier was obtained. Furthermore, the tendency to increase the volume of the unitary cell with the increase of dopant concentration, which was interrupted in the system with 0.25 % Nb2O5, was another evidence that suggested the occurrence of Nb2O5 segregation in the grain boundaries, or even that the reduction in the average grain size could possibly dilute Nb2O5 concentration in the grain boundaries. The average grain size was calculated through SEM micrographs and ranged from 7 to 16 μm, with larger sizes occurring for lower dopant concentrations and presenting higher porosity and lower uniformity in the grains shape. 相似文献
16.
Prabhakaran Sreekumari Anjana Isuhak Naseema Jawahar Mailadil Thomas Sebastian 《Journal of Materials Science: Materials in Electronics》2009,20(7):587-596
(1 − x)ZnNb2O6–xZn3Nb2O8 mixed phase ceramics have been prepared by conventional solid state ceramic route by both mixing ZnO with Nb2O5 and by ZnNb2O6 with Zn3Nb2O8, respectively. The sintered ceramics have high relative permittivity (ε
r
= 23–25), high quality factor (Q
u
xf) up to 95,500 GHz and temperature coefficient of resonant frequency (τ
f
) in the range −55 to −73 ppm/°C. The quality factors are higher for the mixtures when prepared from ZnNb2O6 and Zn3Nb2O8. The 0.5ZnNb2O6–0.5Zn3Nb2O8 has Q
u
xf = 95,500 GHz (at 5.16 GHz), ε
r
= 22.7 and τ
f
= −65 ppm/°C when sintered at 1200 °C. The τ
f
of the ceramic has been tuned close to zero by the addition of ZnTa2O6, which has a positive τ
f
. The ceramic composition (1 − y)[0.5ZnNb2O6–0.5Zn3Nb2O8]–yZnTa2O6 with y = 0.91 shows ε
r
= 34.7 and Q
u
xf = 41,950 GHz (at 4.63 GHz) and zero τ
f
. In order to lower the sintering temperature of 0.5ZnNb2O6–0.5Zn3Nb2O8 ceramic for low temperature co-fired ceramic applications, low melting additives such as CuO, B2O3 and ACuB2O5 (A—Ba, Sr, Zn, Ca) have been added. 12 wt% ZnCuB2O5 added 0.5ZnNb2O6–0.5Zn3Nb2O8 ceramic sintered at 875 °C has Q
u
xf = 39,750 GHz (at 5.89 GHz), ε
r
= 18.3 and τ
f
= −88 ppm/°C. 相似文献
17.
Jae-Hwan Park Byung-Kook Kim Kug-Hyun Song Soon Ja Park 《Journal of Materials Science: Materials in Electronics》1995,6(2):97-101
The effects of Nb2O5 addition and MnO2Nb2O5 co-addition on the piezoelectric properties of Pb(Zr0.53Ti0.47)O3 (PZT) ceramics are investigated. When Nb2O5 is added to PZT, the planar coupling factor (K
p) significantly increases but the mechanical quality factor (Q
M) as well as the electrical quality factor (Q
E) decreases. When MnO2 and Nb2O5 are co-doped, Q
M increases remarkably while K
p rarely changes. This increase in Q
M is ascribed to the domain pinning by Mn as is the case of previously reported MnO2-doped PZT, and the negligible change in K
p is ascribed to the barely changed tetragonality. Even though MnO2-Nb2O5 co-doped PZT shows a smaller induced strain than that of Nb2O5- doped PZT, excellent temperature stability is obtained. It is shown that MnO2Nb2O5 co-doped PZT may be a very suitable material for high-power piezoelectric actuators because of its high K
p, Q
M and Q
E, its low dielectric constant and its excellent temperature stability. 相似文献
18.
19.
Xiaoyan Liu Yongping Pu Pin Li Ting Wu Pan Gao 《Journal of Materials Science: Materials in Electronics》2014,25(7):3044-3051
Ferroelectric glass-ceramics of the SrO–BaO–Nb2O5–CaO–SiO2–B2O3 system with different nucleating agents Cr2O3, BaF2, ZrO2, CaF2 and CeO2, have been prepared by conventional melt casting followed by controlled crystallization processing. The effect of different nucleating agent additions on crystallization mechanism, crystallization behaviors, microstructures and dielectric properties of the glass-ceramics are studied using DTA, XRD techniques, SEM and LCR analyzer. The results show that the addition of different nucleating to the glass-ceramics decreases the crystallization temperatures, accelerates the secondary phase elimination and promotes the uniform distribution of grain size. The well development of microstructure promoted by the nucleating agents can result in the improvement of the dielectric constant as well as energy storage density remarkably. The sample with CeO2 as the optimum nucleating agent achieves the dielectric constant of 301, breakdown strength of 622 kV/cm and the highest energy storage density of 5.15 J/cm3. 相似文献
20.
El-Meliegy E Hamzawy EM El-Kady AM Salama A El-Rashedi A 《Journal of materials science. Materials in medicine》2012,23(9):2069-2080
Osteoconductive bioglasses, free of K(2)O and Al(2)O(3) and with content of Na(2)O lower than 10?mol%, were designed based on the ratio (SiO(2)?+?MgO)/(P(2)O(5)?+?CaO?+?Na(2)O) in the system Na(2)O-CaO-MgO-P(2)O(5)-SiO(2). The developed glasses have shown a strong potential for the formation of hydroxycarbonated apatite (HCA) in vitro. The particles of HCA aggregates tend to be of finer size with increasing the ratio of (SiO(2)?+?MgO)/(CaO?+?P(2)O(5)?+?Na(2)O) in the glass chemical composition indicating significant bioactivity. Critical size bone defects created in the femurs of albino adult female rats, and grafted with the glass particles for 12?weeks post implantation, were completely healed by filling with mineralized bone matrix without infection showing a strong potential for new bone formation in vivo. Osteoblasts and osteocytes were observed close to the surface of the granular implants with active areas of bone deposition, resorption and remodelling. The bioglass with lowest (SiO(2)?+?MgO)/(CaO?+?P(2)O(5)?+?Na(2)O) ratio has shown the highest bioactivity while the bioglass with the highest (SiO(2)?+?MgO)/(CaO?+?P(2)O(5)?+?Na(2)O) has shown the lowest bioactivity. The newly formed bone in vivo has shown a similar structure to that of the original bone as indicated by the histology and microstructural results. In addition, Ca/P molar ratio of the newly formed bone was found to be (~1.67), which is similar to that of the original bone. 相似文献