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1.
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
2.
Kyoung R. Han Soyoung Park Young-Soon Kwon Chang Sam Kim 《Journal of Electroceramics》2006,17(2-4):965-970
Low-temperature-sinterable PMN-PT-BT [0.96 (0.91Pb(Mg1/3Nb2/3)O3-0.09PbTiO3)-0.04BaTiO3] powder was first prepared by the modified mixed oxide method and then metal (M = Cu, Mg, Ag) oxides were introduced as their
nitrate salts. Precalcined PMN-PT-BT/MO composite powders were surface modified with the magnesia sol to suppress diffusion
of Ag or metal oxides. Such prepared composite powders were sintered > 98% T.D. at 850–900∘C and showed homogeneous microstructures with <100 nm Ag or metal oxide particles. Nanoparticles were located mostly in grains
and some on grain boundaries. Grain growth was substantially inhibited and resulted in grain size of ∼2 μm. The nanocomposites
of PBT/Ag and PBT/MgO showed substantially improved sintered densities and dielectric properties at sintering temperature
below 1000∘C, but the PBT/CuO composite was hardly affected. The PBT/Ag composites treated with the MgO sol showed good handling strength
of MOR > 120 MPa. The proper amount of the magnesia sol for surface modification seemed to be 0.5–1.0 wt. 相似文献
3.
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
4.
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
5.
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
6.
Ceramics of 0.2CaTiO3-0.8Li0.5Nd0.5TiO3) have been prepared by the mixed oxide route using additions of Bi2O3-2TiO2 (up to 15 wt%). Powders were calcined 1100∘C; cylindrical specimens were fired at temperatures in the range 1250–1325∘C. Sintered products were typically 95% dense. The microstructures were dominated by angular grains 1–2 μm in size. With increasing
levels of Bi2O3-2TiO2 additions, needle and lath shaped second phases developed. For Bi2Ti2O7 additions up to 5 wt%, the relative permittivity increased from 95 to 131, the product of dielectric Q value and measurement frequency increased from 2150 to 2450 GHz and the temperature coefficient of resonant frequency (τ
f
) increased from −28pp/∘C to +22pp/∘C. A product with temperature stable τ
f
could be obtained at ∼2 wt% Bi2Ti2O7 additions. For high levels of additives, there is minimal change in relative permittivity, the Qxf values degrade and τ
f
becomes increasingly negative. 相似文献
7.
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
8.
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
9.
Barium bismuth niobate, Ba(1-x)Bi(2+2x/3)Nb2O9 (BBN with x = 0.0, 0.1, 0.2, 0.3, 0.4) ceramic powders in the nanometer range were prepared by chemical precursor decomposition method
(CPD). The single phase layered perovskite was prepared throughout the composition range studied. No intermediate phase was
found during heat treatment at and above 600°C. The crystallite size and the particle size, obtained from XRD and TEM respectively,
were in the range of 15–30 nm. The addition of Bi2O3 substantially improved the sinterability associated with high density (96%) which was otherwise difficult in the case of
pure BaBi2Nb2O9 (BBN x = 0.0). The sintering was done at 900°C for 4 h. The relative permittivity of BBN ceramics at both room temperature and in
the vicinity of the temperature of maximum permittivity (Tm) has increased significantly with increase in bismuth content and loss is also decreased to a certain level of bismuth doping.
Tm increased with increase in Bi2O3. The diffuseness (γ) in the phase transition was found to increase from 1.54 to 1.98 with the increase in Ba2+ substitution level from x = 0.0 to x = 0.3. 相似文献
10.
Joo-Sin Lee 《Journal of Electroceramics》2006,17(2-4):709-711
The densification behavior and grain growth of Ce0.8Gd0.2O1.9 ceramics were investigated with the strontium gallate concentration ranging from 0 to 5 mol%. Both the sintered density and
grain size were found to increase rapidly up to 0.5 mol% Sr2Ga2O5, and then to decrease with further addition. Dense Ce0.8Gd0.2O1.9 ceramics with 97% of the theoretical density could be obtained for 0.5 mol% Sr2Ga2O5-added specimen sintered at 1250∘C for 5 h, whereas pure Ce0.8Gd0.2O1.9 ceramics needed to be sintered at 1550∘C in order to obtain an equivalent theoretical density. The addition of Sr2Ga2O5 was found to promote the sintering properties of Gd2O3-doped CeO2. 相似文献
11.
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
12.
Electrical properties and sintering behaviors of (1 − x)Pb(Zr0.5Ti0.5)O3-xPb(Cu0.33Nb0.67)O3 ((1 − x)PZT-xPCN, 0.04 ≤ x ≤ 0.32) ceramics were investigated as a function of PCN content and sintering temperature. For the specimens
sintered at 1050∘C for 2 h, a single phase of perovskite structure was obtained up to x = 0.16, and the pyrochlore phase, Pb2Nb2O7 was detected for further substitution. The dielectric constant (ε r), electromechanical coupling factor (Kp) and the piezoelectric coefficient (d
33) increased up to x = 0.08 and then decreased. These results were due to the coexistence of tetragonal and rhombohedral phases in the composition
of x = 0.08. With an increasing of PCN content, Curie temperature (Tc) decreased and the dielectric loss (tanδ) increased. Typically, εr of 1636, Kp of 64% and d33 of 473pC/N were obtained for the 0.92PZT-0.08PCN ceramics sintered at 950∘C for 2 h. 相似文献
13.
Jong-Yoon Ha Ji-Won Choi Chong-Yun Kang Seok-Jin Yoon Doo Jin Choi Hyun-Jai Kim 《Journal of Electroceramics》2006,17(2-4):399-403
The effect of the addition of glass on the densification, low temperature sintering, and microwave dielectric properties of
the Ca[(Li1/3Nb2/3)1−x
Tix]O3−δ(CLNT) was investigated. Addition of glass (B2O3-ZnO-SiO2-PbO system) improved the densification and reduced the sintering temperature from 1150∘C to 900∘C of Ca[(Li1/3Nb2/3)1−x
-Tix]O3−δ microwave dielectric ceramics. As increasing glass contents from 10 wt% to 15 wt%, the dielectric constants (εr) and bulk density were increased. The quality factor (Q⋅f0), however, was decreased slightly. The temperature coefficients of the resonant frequency (τf) shifted positive value as increasing glass contents over Ti content is 0.2 mol. The dielectric properties of Ca[(Li1/3Nb2/3)0.75Ti0.25]O3−δ with 10 wt% glass sintered at 900∘C for 3 h were εr = 40 Q·f0 = 11500 GHz, τf = 8, ppm/°C. The relationship between the microstructure and dielectric properties of ceramics was studied by X-ray diffraction
(XRD), and scanning electron microscope (SEM). 相似文献
14.
The electric mechanisms of perovskite-type LaMnO3 was investigated with B-site substitution in this paper. Samples of La(TixMn1 − x)O3 (0.1 ≰ x ≰ 0.7) were sintered at different temperature. The voltage-temperature (V-T) curves of the samples were tested from room
temperature (25∘C) to 300∘C, then the electric properties were measured and analyzed. The experimental results showed that the resistivity-temperature
(ρ-T) curves of the samples matched NTC characteristic. The resistivity increased slightly with the increase of Ti amount as x was less than 0.5, however, it rose greatly after x exceeded 0.5; The sintering temperatures have a little influence on the resistivity, except for the sample with x = 0.7. 相似文献
15.
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
16.
Microwave dielectric properties of low temperature sintering ZnNb2O6 ceramics doped with CuO-V2O5-Bi2O3 additions were investigated systematically. The co-doping of CuO, V2O5 and Bi2O3 can significantly lower the sintering temperature of ZnNb2O6 ceramics from 1150 to 870C. The secondary phase containing Cu, V, Bi and Zn was observed at grain boundary junctions, and the amount of secondary phase increased with increasing CuO-V2O5-Bi2O3 content. The dielectric properties at microwave frequencies (7–9 GHz) in this system exhibited a significant dependence on the relative density, content of additives and microstructure of the ceramics. The dielectric constant ( r) of ZnNb2O6 ceramics increased from 21.95 to 24.18 with increasing CuO-V2O5-Bi2O3 additions from 1.5 to 4.0 wt%. The quality factors (Q× f) of this system decreased with increasing CuO-V2O5-Bi2O3 content and ranged from 36118 to 67100 GHz for sintered ceramics, furthermore, all Q× f values of samples with CuO-V2O5-Bi2O3 additions are lower than that of un-doped ZnNb2O6 ceramics sintered at 1150C for 2 h. The temperature coefficient of resonant frequency ( f) changed from –33.16 to –25.96 ppm/C with increasing CuO-V2O5-Bi2O3 from 1.5 to 4.0 wt% 相似文献
17.
Ba(Zn1/3X2/3)O3 materials where X = Ta or Nb (respectively named BZT and BZN) exhibit attractive properties suitable for applications in type I Multi Layer Ceramics Capacitors (MLCC). Nevertheless, to produce such components using Base Metal Electrodes such as copper, a significant reduction of their sintering temperature is required. The aim of this work is first to study the effects of glass phases additions and secondly the stoichiometry influence on the sintering temperature of BZT and BZN. It is shown for example, that our materials can be sintered in air at a temperature lowered by 450C when sintering agents (B2O3 with LiF) are combined with a slight non-stoichiometry. The sintered samples are characterised in terms of final density, microstructure and phase content and it was underlined that such modifications (additions and stoichiometry) does not affect the dielectric properties. 相似文献
18.
LSM-YSZ composite electrodes are prepared from a mixture of YSZ and LSM particles. Commercial YSZ particles were mixed with
polymerizable complex method-driven LSM powders of two different particle sizes, 81 and 210 nm. The correlations between sintering
temperature, microstructure and performance of composite cathode have been studied. It was found that optimum sintering temperature
differs depending upon the LSM particle size. The composite cathode derived from finer LSM particles displayed lowest polarization
resistance ∼0.46 Ωcm2 when sintered at 1100∘C, whereas the same resistance was observed for the electrode involving larger LSM sintered at 1200∘C. The microstructural changes evolved during the course of sintering and the resulting electrodes were investigated by scanning
electron microscopy and impedance spectroscopy. 相似文献
19.
Low temperature sintering and microwave dielectric properties of Ba3Ti5Nb6O28 with B2O3 and CuO additions 总被引:1,自引:0,他引:1
Jeong-Ryeol Kim Dong-Wan Kim Sung Hun Yoon Kug Sun Hong 《Journal of Electroceramics》2006,17(2-4):439-443
The low sintering temperature and the good dielectric properties such as high dielectric constant (ε
r
), high quality factor (Q × f), and small temperature coefficient of resonant frequency (TCF) are required for the application of chip passive components
in wireless communication low temperature co-fired ceramics (LTCC). In the present study, the sintering behaviors and dielectric
properties of Ba3Ti5Nb6O28 ceramics were investigated as a function of B2O3-CuO content. The pure Ba3Ti5Nb6O28 system showed a high sintering temperature (1250∘C) and had the good microwave dielectric properties: Q × f of 10,600 GHz, ε
r
of 37, TCF of −12 ppm/∘C. The addition of B2O3-CuO was revealed to lower the sintering temperature of Ba3Ti5Nb6O28, 900∘C and to enhance the microwave dielectric properties: Q × f of 32,500 GHz, ε
r
of 40, TCF of 9 ppm/∘C. From the X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) studies, these phenomena were explained
in terms of the reduction of oxygen vacancies and the formation of secondary phases having the good microwave dielectric properties. 相似文献
20.
Bismith sodium titanate (BNT)-based powders were prepared by conventionally mixed-oxide method using Bi2O3, Na2CO3 and TiO2. The La2O3 was added as the modifier to the BNT composition for easily poling and reducing an abnormal dielectric loss at high temperatures. In this study, the investigated compositions were Bi0.5Na0.5TiO3 and Bi0.5Na0.485La0.005TiO3. The powders were calcined at 900 °C for 2 h by slow heating rate at 100 °C/h. The calcined BNT-based powders were then attrition-milled for 3 h with a high speed at 350 rpm. After drying, the fine powders were uniaxially pressed and then cold-isostatically pressed (CIP) at 240 MPa for 10 min. All pressed pellets were sintered at 1000–1100 °C for 2 h in air atmosphere. The microstructure of sintered pellets was investigated by SEM. Results of dielectric and piezoelectric property measurement were also reported. 相似文献