共查询到20条相似文献,搜索用时 31 毫秒
1.
Shuang Wang Hao Su Liying Chen Haiyi Yuan 《Journal of Materials Science: Materials in Electronics》2010,21(11):1159-1163
The high dielectric constant X8R dielectric materials could be sintered at 1,240 °C by doping 2.5 mol% Pb(Ti,Sn)O3 additives into the BaTiO3 ceramics, with a dielectric constant greater than 3,400 at 25 °C, dielectric loss lower than 2.0% and temperature coefficient
of capacitance (TCC) less than ±15% from −55 to 150 °C, which satisfied X8R specification. The effects of Pb(Ti,Sn)O3 on the microstructure and dielectric properties of BaTiO3-based ceramics were investigated. Doped with Pb(Ti,Sn)O3 additives, the partial solid solution was formed between Pb(Ti,Sn)O3 and BaTiO3. Due to the high Curie point of Pb(Ti,Sn)O3, the Curie point of the ceramics was markedly shifted to higher temperature about 150 °C, and the temperature coefficient
of capacitance curves was flattened. The increase of the tetragonality (c/a ratio) and the fine microstructure were resulted
in the increase of dielectric constant. With Pb(Ti, Sn)O3 content up to 3 mol%, the depression of Ti4+’s polarization and the decrease of the tetragonality (c/a ratio) were resulted in the decrease of dielectric constant. 相似文献
2.
Bo Li Shuren Zhang Xiaohua Zhou Sheng Wang Zhu Chen 《Journal of Materials Science》2007,42(6):2090-2096
BaTiO3-based ultrafine nonreducible dielectrics for multilayer ceramic capacitors were prepared by a newly developed nanocomposite
doping process. According to TG-DTA, XRD and TEM analysis, the nanocomposite dopants via sol–gel method were uniform and well
dispersive. The micromechanism was investigated based on comparing conventional process with nano-doping process. It indicated
that due to the special nano-effect, doping effect of additives became more effective and the microstructure and dielectric
properties of ceramics were improved. The results showed that high performance dielectrics satisfying X8R specification were
achieved, with high dielectric constant of 2,900, low dielectric loss of 0.6% and large insulation resistivity of 1012 Ω cm. 相似文献
3.
Xiaohua Zhou Shuren Zhang Ying Yuan Bo Li Jingsong Liu 《Journal of Materials Science: Materials in Electronics》2006,17(2):133-136
Nonreducible X7R dielectric materials, which can be cofired with Ni electrode, were obtained by doping nanometer additives
to BaTiO3 powders synthesized by employing a sol-gel method. The crystallization process, structure and constituent of nanometer additives,
as well as morphologies were studied via differential thermal and thermogravimetric analyses (DTA/TG), X-ray diffraction (XRD)
and transmission electron microscopy (TEM). The effects of the calcining temperature of dopants on the dielectric properties
were also discussed. The experiment results proved that higher-performance X7R dielectric materials could be obtained via
nanometer doping compared with conventional doping. At room temperature, dielectric constant is more than 3000; dielectric
loss lower than 1.0% and insulation resistance more than 1011Ω ⋅cm. 相似文献
4.
Liying Chen Shunhua Wu Shuang Wang Guoqing Wang 《Journal of Materials Science: Materials in Electronics》2008,19(4):327-331
The relationship between the microstructures and dielectric properties of BaTiO3-based X7R ceramics has been investigated at different calcination temperatures. The XRD and SEM results show that calcinations
of BaTiO3 raw powders increase the grain size and stabilize the tetragonality (c/a ratio) of the ceramics. The grain growth caused by
the calcination prevents the doped ions from diffusing into the interior of the grains, and then increases the volume fraction
of the tetragonal phased core. This process greatly increases the dielectric constant by improving the ferroelectricity. As
a result, the relaxation mechanism of the domain reorientation generates high loss tangent. The BaTiO3 ceramics with X7R specifications were prepared at the calcination temperature of 1200 °C and the sintering temperature of
1240 °C, whose dielectric properties were ɛ
r ≥ 4500, Δɛ
r/ɛ
r25 ≤ ± 10%(−55∼125 °C), tanδ ≤ 0.012(25 °C), respectively. 相似文献
5.
Ying Yuan Min Du Shuren Zhang Zhenlin Pei 《Journal of Materials Science: Materials in Electronics》2009,20(2):157-162
The microstructure and dielectric properties of ternary system BaTiO3 (BT)–Bi0.5Na0.5TiO3 (BNT)–BiNbO4 were investigated. In the case of 1 mol% BNT addition, the Curie point (T
c) of BaTiO3 was increased from 130 to 140 °C. The dielectric constant peak at T
c was markedly depressed with the addition of BiNbO4, whereas an enhancement in the dielectric constant at lower temperature was observed. The addition of BiNbO4 improved the temperature dependence of the dielectric constants of BaTiO3-BNT system ceramics and the temperature coefficient of capacitance curves satisfied the EIA X8R specification with 3–4 mol%
BiNbO4. The dielectric constant peak at T
c was suppressed evidently due to over high-sintering temperature. As the BiNbO4 content was increased, the Curie point progressively moved to lower temperatures. SEM indicated that fine and homogeneous
grains were observed with 1 mol% BiNbO4 addition. However, secondary phase grains appeared with increasing the BiNbO4 content, which were identified as Ba2TiO4, NaBiTi2O6, and BaTiNb4O13 by XRD. Moreover, the proportion of the secondary phase grains increased as the BiNbO4 content increased. 相似文献
6.
Shuang Wang Hao He Hao Su 《Journal of Materials Science: Materials in Electronics》2012,23(10):1875-1880
The high performance X9R ceramics could be sintered at as low as 1,120?°C by doping 3?mol% synthesized BaTiO3 (SB) additives into the BaTiO3-based ceramics, with a dielectric constant greater than 2,200 at 25?°C and dielectric loss lower than 1.7?%. The effects of SB additives on the microstructure and dielectric properties of BaTiO3-based ceramics were investigated. The dielectric constant of BaTiO3-based ceramics doped with 3?mol% SB was increased due to the promotion of the densification of ceramics. With SB content up to 4.5?mol%, Ti4+’s polarization was depressed, which resulted in the decrease of augmented dielectric constant at 25?°C. The partial solid solution was formed between Pb(Ti, Sn)O3 and BaTiO3, and the substitutions of Pb at A-sites and Sn at B-sites were existed. The strengthen of Ti–O bonds and higher Curie point of Pb(Ti0.55Sn0.45)O3 was helpful to increased the Curie point of the ceramics effectively. Doped with SB additives, the volume of ferroelectric core was increased, and the sharp peak intensity at Curie point was increased accordingly. Capacitance temperature characteristics was improved attributed to the mutual effects of SB and Pb(Ti0.55Sn0.45)O3. The formation of core–shell structure was sensitive to the sintering temperature, so the dielectric properties of ceramics were highly depended on the sintering temperature. 相似文献
7.
Ag-doped BaTiO3 based X7R (temperature coefficient of capacitance within the range of ±15% between −55 and +125 °C) ceramics with different amounts of silver (0.0-20.0 mol%) were prepared in this paper. The X-ray diffraction analysis indicated that no phases other than BaTiO3 and silver were observed in the ceramics. The energy dispersive X-ray spectroscopy analysis showed that the silver particles presented homogeneous distribution in the BaTiO3 ceramics. The dielectric properties of Ag-doped ceramics were investigated. A small amount of silver (<0.5 mol%) and a large amount of silver (>2.0 mol%) could both improve the sintered density and permittivity, but more content of silver (0.5-2.0 mol%) would decrease the relative density and permittivity. Specially, the temperature coefficient of capacitors of the ceramics doped with 20 mol% silver still met the X7R characteristics, and the room temperature permittivity of the ceramics was 6823, which was the highest dielectric constant in the BaTiO3 based X7R ceramics. 相似文献
8.
We have studied the effect of heat treatment of the starting BaTiO3 powder on the dielectric properties and microstructure of X7R-type BaTiO3-based ceramics. The results demonstrate that annealing of BaTiO3 stabilizes the degree of tetragonality in the crystal lattice of the ceramics. Microstructural analysis shows that the annealing
temperature has no effect on the average grain size of the ceramics. Increasing the BaTiO3 annealing temperature increases the dielectric permittivity of the core phase and reduces the temperature coefficient of
capacitance (TCC). We obtained an X7R-type BaTiO3-based ceramic material (BaTiO3 annealing temperature, 1150°C; firing temperature, 1160°C) with the following properties: ɛ25°C = 2230, TCC = ±12% (−55 to 125°C), and tanδ25°C = 0.013. 相似文献
9.
The microstructure and dielectric properties of Yb-Mn- and Yb-Ni-substituted BaTiO3 ceramics are investigated in this paper. Both Yb-Mn- and Yb-Ni-substituted BaTiO3 ceramics satisfy the X8R specification (−55 ∘C to 150 ∘C, Δ C = ±15% or less) for automotive application when CaZrO3 is incorporated in the formulations. It is found that both Mn and Ni ions can suppress the diffusion of Yb and CaZrO3 into BaTiO3 grains, resulting in formation of core-shell structures in the grains. It is found that Mn is more favorable to stabilize
the core-shell structure in BaTiO3 ceramics as compared with Ni. 相似文献
10.
Shuang Wang Hao He Hao Su 《Journal of Materials Science: Materials in Electronics》2013,24(7):2385-2389
Medium-temperature sintering X8R ceramics were fabricated based on BaTiO3-based ceramics with Bi2O3 additives. The effects of sintering aids Bi2O3 on crystalline structure and electrical properties of BaTiO3-based ceramics were investigated. The sinterability of BaTiO3 ceramics was significantly improved by adding Bi2O3, whose densification sintering temperature reduced from 1,260 to 1,130 °C. However, the dielectric constant (ε) of BaTiO3-based ceramics doped with Bi2O3 was decreased dramatically. Both low ε phase Bi4Ti3O12 and the decrease of the tetragonality (c/a ratio), which are demonstrated by XRD pattern, are resulted in the decrease of ε. The ε of samples doped with 5.5 wt% Bi2O3 was higher than the other doped samples. The substitution of Bi3+ for the Ba2+ in BaTiO3 resulted in the increase of electrovalence (from +2 to +3) of A-site ion, so the attractive force between A and B (Ti4+) sites becomes stronger. Thus Ti4+’s polarization enhances, then ε was increased to some extent. The X8R BaTiO3-based ceramics could be sintered at as low as 1,130 °C by doping 5.5 wt% Bi2O3 additives into the BaTiO3-based ceramics, with a ε greater than 2,430 at 25 °C, dielectric loss lower than 1.3 % and temperature coefficient of capacitance <±15 % (?55–150 °C). 相似文献
11.
Ch. Sameera Devi M. Vithal G. S. Kumar G. Prasad 《Journal of Materials Science: Materials in Electronics》2011,22(12):1855-1864
Lead free (Ba(1−3x)Nd(2x))(Ti(1−y)Zry)O3 (x = 0, 0.025, y = 0, 0.025, 0.05) ceramics were prepared successfully using sol–gel method. The effect of Nd, Zr content
on dielectric and polarisation properties of BaTiO3 were studied using dielectric and hysteresis measurements. SEM analysis proved that the particle size of compounds as prepared
were in the order of 30–60 nm. The ferroelectric phase transition from tetragonal to cubic phase was observed around 130 °C
for pure BaTiO3. With the addition of Nd (2.5 mol%) and increasing content of Zr (2.5 and 5 mol%), it was observed that transition temperature
(Tc) shifts to lower temperatures (70–50 °C), but didn’t show any relaxor behaviour. Dielectric measurements showed an increase
in the values at room temperature in all the doped samples. The synthesized ceramics exhibited typical P–E hysteresis loops
at room temperature accompanied by saturation polarisation (Ps) and remanent polarisation (Pr). Behaviour of polarisation phenomena in these compounds showed interesting results with increasing temperature. 相似文献
12.
Ling-xia Li Ye-mei Han Ping Zhang Cui Ming Xue Wei 《Journal of Materials Science》2009,44(20):5563-5568
The effects of (Na0.5Bi0.5)TiO3 (NBT) and MgO addition on the dielectric properties and microstructures of BaTiO3 (BT) ceramics were investigated. NBT was first added to Nb2O5-doped BT system. As NBT content increases from 0 to 0.2 mol, the Curie temperature of the systems shifts to high temperatures
and dielectric constant peak at T
c is suppressed evidently. The variation of capacity (ΔC/C
20 °C (%)) of the system at 200 °C decreases with increasing NBT content from 0.1 to 0.2 mol, but that of −55 and 125 °C increases
monotonously. The stable temperature characteristics of the dielectric properties improved by NBT doping would be connected
with the distortion and deformation of the structure induced by substitution of Na+ and Bi3+ into Ba sites. MgO was employed to further flatten the ΔC/C
20 °C–T curve. It is very helpful for this ceramic system to satisfy the requirement of EIA-X9R specification on ΔC/C
20 °C and still keep a satisfied dielectric constant. The addition of MgO improved effectively the temperature stability of the
dielectric properties. Changes of the crystalline structure and microstructure induced by MgO doping might contribute to these
improvements. 相似文献
13.
Qian Qian Jia Hui Ming Ji Xiao Lei Li Yong Hui Xing Hui Liang 《Journal of Materials Science: Materials in Electronics》2011,22(9):1450-1455
Compositionally graded multilayer BaxSr0.95−xCa0.05TiO3 (BSCT) ceramics were prepared via tape casting method using nanometer powders from co-precipitation. Microstructures and
dielectric properties of the BSCT system were investigated. The powders were characterized by using transmission electron
microscope and BET surface area measurement. Surface morphologies of the sintered samples and multilayer structure were examined
by scanning electron microscopy. BSCT particles were of spherical shape with diameters in the range of 73–93 nm. Their specific
surface areas were in the range of 11.7–14.6 m2/g. The graded BSCT ceramics with nine layers laminated in vertical way exhibited a higher sintered density, with an average
grain size of 0.4 μm, after sintered at 1,200 °C. Dielectric constant, dielectric loss and tunability of the graded ceramics
were 2223.94, 1.5 × 10−3 at 2 MHz and 42.9% at 3.0 kV/mm, with good dielectric temperature and frequency stability, which made it a promising candidate
used for tunable ceramic capacitors and phase shifters. 相似文献
14.
15.
Dehua Xiong Hong Li Jinshu Cheng 《Journal of Materials Science: Materials in Electronics》2010,21(9):882-888
Temperature and frequency dependence on electrical properties (dielectric constant, dielectric loss and conductivity) of Li2O–Na2O–K2O–Al2O3–SiO2(R2O–Al2O3–SiO2) system glass–ceramics used as anodic bonding materials were discussed. The results showed that the main crystal phase of
glass–ceramics was lithium metasilicate (Li2SiO3). Compared with the parent glass, both the dielectric constant and dielectric loss of glass–ceramics decreased, the dielectric
constant and dielectric loss increased gradually with the increasing of the test temperature from room temperature to 400 °C,
Testing frequency (30–300 MHz) had very little influence on the dielectric properties of samples. The electrical conductivity
of glass–ceramics showed a trend of first decrease and then increase with the increasing of temperature. The glass–ceramics
which has a lower dielectric constant, dielectric loss and better stability under high frequency was obtained after an appropriate
heat treatment; it could be used as anodic bonding materials under very high frequency. 相似文献
16.
In this work, the effects of Nb2O5 addition on the dielectric properties and phase formation of BaTiO3 were investigated. A core–shell structure was formed for Nb-doped BaTiO3 resulted from a low diffusivity of Nb5+ ions into BaTiO3 when grain growth was inhibited. In the case of 0.3–4.8 mol% Nb2O5 additions, two dielectric constant peaks were observed. The Curie dielectric peak was determined by the ferroelectric-paraelectric
transition of grain core, whereas the secondary broad peak at lower temperature was due to strong chemical inhomogeneity in
Nb-doped BaTiO3 ceramics. The dielectric constant peak at Curie temperature was markedly depressed with the addition of Nb2O5. On the other hand, the secondary dielectric constant peak was enhanced when sintered above 1280 °C for higher Nb2O5 concentrations (≥1.2 mol%). The Curie temperature was shifted to higher temperatures, whereas the transition temperature
corresponding to the secondary peak moved to lower temperatures as increasing the amount of Nb2O5 more than 1.2 mol%. The decrease of this lower transition temperature was assumed to be closely related with the secondary
phase formation when Nb concentration greater than 1.2 mol%. From XRD analyses, a large amount of secondary phases was observed
when Nb2O5 amount exceeded 1.2 mol%. The coefficients of thermal expansion of Nb-doped BaTiO3 were increased with increasing Nb2O5 contents, resulting in large internal stress between cores and shells. Therefore, the shift of Curie temperature to higher
temperatures was attributed to internal stress resulting from the formation of a core–shell structure and a large amount of
secondary phase grains. 相似文献
17.
Wave-transparent materials used at high temperature environment generated by high supersonic and hypersonic speeds must possess
excellent mechanical property. In this paper, porous Si3N4 ceramics with high strength were fabricated by low molding pressure (10 MPa) and pressureless sintering process, without
any other pore forming agents. The sintering behavior and the effect of porosity on the mechanical strength and dielectric
properties were investigated. The flexural strength of porous Si3N4 ceramics was up to 57–176 MPa with porosity of 45–60%, dielectric constant of 2.35–3.39, and dielectric loss of 1.6–3.5 × 10−3 in the frequency range of 8–18 GHz, at room temperature. With the increase of porosity, the flexural strength, dielectric
constant, and dielectric loss all decreased. 相似文献
18.
Ying Yuan Shuren Zhang Changmin Li 《Journal of Materials Science: Materials in Electronics》2004,15(9):601-606
The effect of doping process on the dielectric properties, sintering behavior and microstructure were investigated on the BaTiO3–Nb2O5–Co3O4 ternary system ceramic. Temperature stable dielectric ceramics were obtained by different doping processes if only appropriate Nb5++Co3+ amount and Nb5+/Co3+ ratio were adopted. The dielectric constant was enhanced to the largest extent by nanometer oxide doping and the temperature characteristic satisfied the X7R specification. Two kinds of grains were observed in all the samples: matrix grains (BaTiO3) and the secondary phase grains (Ba6Ti17O40) formed by the incorporation of Nb5+ and Co3+ into BaTiO3 lattice and Ti4+ segregation. The matrix grains were about 1 m in diameter and showed little grain growth with increasing temperature in all the doped samples, whereas the sizes of the secondary phase grains were strongly dependent on the doping process. The secondary phase formed liquid phase during firing, but the liquid phase contributed little to the densification of ceramics. 相似文献
19.
Reenamoni Saikia Chaliha V. S. Tiwari P. K. Gupta K. Annapurna Anal Tarafder Basudeb Karmakar 《Journal of Materials Science: Materials in Electronics》2011,22(7):728-734
Glasses in the composition of 25K2O-25Nb2O5-50SiO2 (mol %) have been prepared by melt quenching technique and isothermally heat-treated at 800 °C for different duration (0–200 h).
The formed nanocrystalline KNbO3 phase, crystallite size and morphology are examined by X-ray diffraction, Fourier transform infrared reflection spectroscopy,
field emission scanning and transmission electron microscopes. The frequency and temperature dependent dielectric constant
and loss tangent are measured in the frequency and temperature ranges 0.1–1000 kHz and 200–500 °C respectively. The dielectric
constant and loss tangent are found to decrease with increasing frequency and increase with increasing temperature. The dielectric
constant and loss tangent versus temperature curve at different frequency revealed the phase transition of KNbO3 from paraelectric cubic to ferroelectric tetragonal around 425 and 397 °C (Curie temperature) for nano glass–ceramics obtained
after 1 and 200 h heat-treatment respectively. 相似文献
20.
Lanfang Gao Yanqiu Huang Liang Liu Tiantian Liu Chunfeng Liu Fei Zhou Xinwu Wan 《Journal of Materials Science》2008,43(18):6267-6271
(1 − x)BaTiO3–x(Bi0.5Na0.5)TiO3 (x ranged from 0.01 to 0.96) ceramics were fabricated by the conventional ceramic technique. The crystal structure, as well
as dielectric and piezoelectric properties of the ceramics were studied. All the ceramics formed single-phase solid solutions
with perovskite structure after sintering in air at 1150–1250 °C for 2–4 h. The crystal structure and microstructure varied
gradually with the increase of (Bi0.5Na0.5)TiO3 (BNT) content. The Curie temperature, T
c, shifted monotonously to high temperature as BNT increased. The ceramics with 20–90 mol% BNT had relatively low and stable
dielectric loss characteristics. The piezoelectric constant, d
33, enhanced with the increase of BNT content through a maximum value in a composition of 93 mol% BNT and then tended to decrease.
The maximum value, 148 pC/N, of piezoelectric constant d
33 together with the electromechanical coupling factors, k
t, 19.8% and k
p, 15.8%, were obtained when BNT was 93 mol%. 相似文献