共查询到20条相似文献,搜索用时 15 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.
Mahamoud S. Alkathy K. C. James Raju 《Journal of Materials Science: Materials in Electronics》2016,27(9):8957-8965
Polycrystalline Sr(1–x)(Bi, Li)xTiO3 ceramics (x = 0 and 0.02) are prepared by a microwave processing method. The effect of co-substitution on structural, dielectric properties and ac-conductivity were investigated. The XRD of ceramics shows single phase with cubic structure. The lattice parameter of the compounds is estimated from the XRD patterns which confirm the incorporation of Bi and Li in SrTiO3 ceramics. Studies revealed that the dielectric constant and dielectric loss increased with an increase of temperature and decreased with an increase in frequency. The maximum dielectric constant obtained at room temperature is around 570 and increased to around 104 at 600 °C measured at 1 kHz frequency whereas the maximum dielectric loss measured was 0.048 at 600 °C and the loss measured at room temperature is 0.02. The activation energy of the samples were investigated using Arrhenius plots. 相似文献
3.
W. Z. Yang C. L. Song X. Q. Liu H. Y. Zhu X. M. Chen 《Journal of Materials Science》2011,46(19):6339-6343
Single tetragonal La1.5Sr0.5CoO4 ceramics with the space group of I 4/mmm (139) were prepared by a solid-state reaction process, and dielectric characteristics were investigated on a broad frequency
and temperature range. There was one obvious dielectric relaxation around room temperature plus a low temperature upturn on
the curve of temperature dependence of dielectric properties for La1.5Sr0.5CoO4 ceramics. This dielectric relaxation was a thermal-activated process. It should be attributed to the mixed-valence structure
(Co2+/Co3+) since its activation energy was similar to that of small polaronic hopping process. After annealing the sample in O2 atmosphere, dielectric constants and ac conductivities of La1.5Sr0.5CoO4 ceramics increased and decreased after annealing the sample in N2 atmosphere. This abnormal phenomenon should be attributed to the variation of concentration for holes (Co3+). 相似文献
4.
X. H. Zheng X. M. Chen Y. W. Zeng 《Journal of Materials Science: Materials in Electronics》2005,15(11):733-737
The effects of La/Sn co-substitution for Ba/Ta were investigated for the modification of Ba5NdTi3Ta7O30 ceramics. The modified ceramics (Ba5–x
La
x
)NdTi3(Ta7–x
Sn
x
)O30 exhibited single tetragonal tungsten bronze phase for x<1.5, while a small amount of secondary phase BaTi4O9 was observed for x>1.5. The lattice constants decreased with increasing La/Sn content, while the axial ratio 101/2c/a decreased when x was below 1.5, then slightly increased. With increasing La and Sn content, the temperature coefficient of dielectric constant (at 1 MHz) was remarkably lowered from –1560 ppm/ °C to –286 ppm/ °C, while the dielectric constant gradually reduced, and the dielectric loss slightly increased. There were some clear relationships between the temperature coefficient and bond valence, tolerance factor: the temperature coefficient of dielectric constant linearly increased when the bond valence of the ions at B sites increased, while the same effect occurred when the tolerance factor decreased. In addition, the stability of the tetragonal tungsten bronze phase is discussed in relation to electronic difference and tolerance factor. 相似文献
5.
X. H. Zheng X. M. Chen Y. W. Zeng 《Journal of Materials Science: Materials in Electronics》2004,15(11):733-737
The effects of La/Sn co-substitution for Ba/Ta were investigated for the modification of Ba5NdTi3Ta7O30 ceramics. The modified ceramics (Ba5?x La x )NdTi3(Ta7?x Sn x )O30 exhibited single tetragonal tungsten bronze phase for x<1.5, while a small amount of secondary phase BaTi4O9 was observed for x>1.5. The lattice constants decreased with increasing La/Sn content, while the axial ratio 101/2c/a decreased when x was below 1.5, then slightly increased. With increasing La and Sn content, the temperature coefficient of dielectric constant (at 1 MHz) was remarkably lowered from ?1560 ppm/ °C to ?286 ppm/ °C, while the dielectric constant gradually reduced, and the dielectric loss slightly increased. There were some clear relationships between the temperature coefficient and bond valence, tolerance factor: the temperature coefficient of dielectric constant linearly increased when the bond valence of the ions at B sites increased, while the same effect occurred when the tolerance factor decreased. In addition, the stability of the tetragonal tungsten bronze phase is discussed in relation to electronic difference and tolerance factor. 相似文献
6.
Liang Fang Zhao Yang Hui Zhang Chunchun Li Xiyang Peng Changzheng Hu Dongjin Chu 《Journal of Materials Science: Materials in Electronics》2011,22(9):1208-1212
Polycrystalline samples of Ba4Ln2Fe2Ta8O30 (Ln = La and Nd) were prepared by a high temperature solid-state reaction technique. The formation, structure, dielectric
and ferroelectric properties of the compounds were studied. Both compounds are found to be paraelectrics with filled tetragonal
tungsten bronze (TB) structure at room temperature. Dielectric measurements revealed that the present ceramics have exceptional
temperature stability, a relatively small temperature coefficient of dielectric constant (τ
ε
) of −25 and −58 ppm/°C, with a high dielectric constant of 118 and 96 together with a low dielectric loss of 1.2 × 10−3 and 2.8 × 10−3 (at 1 MHz) for Ba4La2Fe2Ta8O30 and Ba4Nd2Fe2Ta8O30, respectively. The measured dielectric properties indicate that both materials are possible candidates for the fabrication
of discrete multilayer capacitors in microelectronic technology. 相似文献
7.
Y. X. Mao H. L. Pan Y. W. Zhang Q. Q. Liu H. T. Wu 《Journal of Materials Science: Materials in Electronics》2017,28(18):13278-13282
Li2Mg3SnO6 (abbreviation for LMS) ceramics doped with 1–4 wt% lithium fluoride (LiF) were prepared by the conventional solid-state reaction method. The effects of LiF addition on the phase compositions, sintering behaviors and microwave dielectric properties of LMS ceramics were investigated. A small amount of LiF addition could effectively decrease the sintering temperatures due to the liquid phase in the sintering process and induced no apparent degradation of the microwave dielectric properties. The optimized quality factor values for each composition firstly increased and then decreased with the increase of the LiF content. Whereas, the optimized dielectric permittivity increased with increasing of the LiF content. Distinguished microwave dielectric properties with a dielectric constant (ε r) of 11.13, a quality factor (Q·f) of 104,750 GHz, and a temperature coefficient of resonant frequency (τ f ) of ?10.83 ppm/°C were obtained for LMS ceramics sintered at 950?°C doped with 3 wt% LiF, which showed that the materials were suitable for the low temperature co-fired ceramics applications (LTCC). 相似文献
8.
Zixing Wang Changlai Yuan Baohua Zhu Qin Feng Fei Liu Lei Miao Changrong Zhou Guohua Chen 《Journal of Materials Science: Materials in Electronics》2018,29(3):1817-1822
A novel microwave dielectric ceramics Bi(Sc1/3Mo2/3)O4 with low firing temperature were prepared via the solid reaction method. The specimens have been characterized using scanning electron microscopy, X-ray diffraction, Raman spectroscopy and DC conductivity. The Bi(Sc1/3Mo2/3)O4 ceramics showed B-site ordered Scheelite-type structure with space group C2/c. Raman analysis indicated that prominent bands were attributed to the normal modes of vibration of MoO4 2? tetrahedra. The dielectric loss of Bi(Sc1/3Mo2/3)O4 ceramics can be depended strongly the bulk conductivity by DC measurement. The superior microwave dielectric properties are achieved in the Bi(Sc1/3Mo2/3)O4 ceramic sintered at 875 °C/4 h, with dielectric constant?~?25, Q?×?f ~?51,716 GHz at 6.4522 GHz and temperature coefficient of resonance frequency ~???70.4 ppm/°C. It is a promising microwave dielectric material for low-temperature co-fired ceramics technology. 相似文献
9.
Suhua Fan Fengqing Zhang Guitao Liu Qingbo Tian Luyi Zhu 《Journal of Materials Science: Materials in Electronics》2011,22(12):1778-1782
Bismuth-layered compound Ca0.15Sr1.85Bi4−xNdxTi5O18 (CSBNT, x = 0–0.25) ferroelectric ceramics samples were prepared by solid-state reaction method. The effects of Nd3+ doping on their ferroelectric and dielectric properties were investigated. The remnant polarization Pr of CSBNT ceramics
increases at beginning then decreases with increasing of Nd3+ doping level, and a maximum Pr value of 9.6 μC/cm2 at x = 0.05 was detected with a coercive field Ec = 80.2 kV/cm. Nd3+ dopant not only decreases the Curie temperature linearly, but also the dielectric constant (εr) and dielectric loss tangent (tan δ). The magnitudes of εr and tan δ at the frequency of 100 kHz are estimated to be 164 and 0.0083 at room temperature, respectively. 相似文献
10.
Gd3+ was chosen as a substitute for Bi3+ in BiNbO4 ceramics, and the substitution effects on the sintering performance and microwave dielectric properties were studied in this
paper. The high temperature triclinic phase was observed only in the Bi0.98Gd0.02NbO4 ceramics when sintered at 920 °C. Both bulk densities and dielectric constant (εr) increased with the sintering temperature, while decreased with the Gd content. The quality factor (Q) exhibited a correlation to the Gd content and the microstructures of Bi1−x
Gd
x
NbO4 ceramics. At the sintering temperature of 900 °C, Bi0.992Gd0.008NbO4 ceramics exhibited microwave dielectric properties of εr ∼ 43.87, Q × f ∼ 16,852 GHz (at 4.3 GHz), and its temperature coefficient of resonant frequency (τf) was found to be near-to-zero. 相似文献
11.
Wang-Suo Xia Lan-Yang Zhang Ying Wang Jun-Ting Zhang Rong-Rong Feng Li-Wei Shi 《Journal of Materials Science: Materials in Electronics》2017,28(24):18437-18441
Microwave dielectric ceramics CuO–modified MgZrTa2O8 were synthesized by the conventional solid-state reaction method. The effects of CuO additives on the sintering characteristics and microwave dielectric properties have been investigated. With CuO addition, the sintering temperature of MgZrTa2O8 ceramics can be effectively lowered from 1475 to 1375 °C without decreasing its dielectric properties obviously and the temperature coefficient of the resonant frequency of MgZrTa2O8 ceramics have been optimized to near-zero. The crystalline phase exhibited a wolframite crystal structure and no second phase was detected at low addition levels. The grain growth of CuO–modified MgZrTa2O8 ceramics was accelerated due to liquid phase effect. The relative dielectric constants (εr) were correlated with apparent density and were not significantly different for all levels of CuO concentration. The quality factors (Q?×??) and temperature coefficient of resonant frequency (τ?), which were strongly dependent on the CuO concentration, were analyzed by the grain size and the dielectric constant respectively. A best Q?×?? value of 116400 GHz and τ? value of ?6.19 ppm/℃ were obtained for specimen with 0.05 wt% CuO addition at 1375 °C. 相似文献
12.
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
13.
Longhai Yang Xiaolian Chao Lingling Wei Nan Zhao Zupei Yang 《Journal of Materials Science: Materials in Electronics》2016,27(3):2221-2227
Na0.65Bi0.45Cu3Ti4O12 ceramics were successful prepared by the conventional solid-state reaction technique. Compared to Na0.50Bi0.50Cu3Ti4O12 (NBCTO), the composition of Na0.65Bi0.45Cu3Ti4O12 was designed in terms of changing the Na/Bi ratio. Colossal dielectric permittivity of ~1.2 × 104 at 1 kHz was obtained in Na0.65Bi0.45Cu3Ti4O12 ceramics. Interestingly, three frequency dispersions were observed in the frequency dependence of dielectric constant measured at different temperatures. The investigation of electric modulus displayed that the giant low-frequency dielectric constant was attributed to Maxwell–Wagner polarization at the grain boundaries and the frequency dispersion in middle-frequency range was due to the grain polarization. Except grain response and grain boundaries response reflected by two semicircles in the impedance spectroscopy, another electrical response associated with nonzero high frequency intercept was found. The grain resistance Rg and grain boundaries resistance R gb was ~600 Ω and 3.9 × 105 Ω, respectively. The large intrinsic permittivity as high as ~700 was obtained. Furthermore, two dielectric anomalies observed in the temperature dependent of dielectric constant were discussed in detail. The results indicated change in the Na/Bi ratio had a significant effect on the electrical properties of NBCTO ceramics. 相似文献
14.
Pure and Zr-substituted CaCu3(Ti1−x
Zr
x
)4O12 (x = 0, 0.01, 0.02, 0.03) ceramics were prepared by the Pechini method. X-ray powder diffraction analysis indicated the formation
of single-phase compound, and all the diffraction peaks were completely indexed by the body-centered cubic perovskite-related
structure. The effects of Zr4+ ion substituting partially Ti4+ ion on the dielectric properties were investigated in frequency range between 100 Hz and 1 GHz. The low frequency (f ≤ 105 Hz) dielectric constant decreases with Zr substitution and the high frequency (f ≥ 107 Hz) dielectric constant is unchanged. Interestingly, a low-frequency relaxation was observed at room temperature through
Zr substitution. The observed dielectric properties in Zr-substituted samples were discussed using the internal barrier layer
capacitor model. A corresponding equivalent circuit was adopted to explain the dielectric dispersion. The characteristic frequency
of low-frequency relaxation rises due to the decrease of the resistivity of grain boundary with Zr substitution, which is
likely responsible for the large low-frequency response at room temperature. 相似文献
15.
Ying Wang Lei Ni Xiang Ming Chen 《Journal of Materials Science: Materials in Electronics》2011,22(4):345-350
Ca1−3x/2Nd
x
Cu3Ti4O12 (x = 0, 0.1, 0.2) ceramics were prepared by a solid state reaction process, and single-phased structures were obtained for all
the compositions. The dielectric characteristics of pure and Nd-substituted CaCu3Ti4O12 ceramics were investigated together with the microstructures. The mixed-valent structures of Cu+/Cu2+ and Ti3+/Ti4+ in the present ceramics were confirmed by X-ray photoelectron analysis. The dielectric relaxation in the low temperature
range was examined in detail and the variation of dielectric constant and dielectric loss was attributed to the modification
mixed-valent structures. 相似文献
16.
The effects of CuO–Bi2O3–V2O5 additions on the sintering temperature and the microwave dielectric properties of MgTiO3 ceramics were investigated systematically. The CuO–Bi2O3–V2O5 (CuBiV) addition significantly lowered the densification temperature of MgTiO3 ceramics from 1400 °C to about 900 °C, which is due to the formation of the liquid-phase of BiVO4 and Cu3(VO4)2 during sintering. The saturated dielectric constant (εr) increased, the maximum quality factor (Qf) values decreased and the temperature coefficient of resonant frequency (τf) shifted to a negative value with the increasing CuBiV content, which is mainly attributed to the increase of the second
phase BiVO4. MgTiO3 ceramics with 6 wt.% CuBiV addition sintered at 900 °C for 2 h have the excellent microwave dielectric properties: ε r= 18.1, Qf = 20300 GHz and τf = −57 ppm/ °C. 相似文献
17.
R. N. P. Choudhary Dillip K. Pradhan C. M. Tirado G. E. Bonilla R. S. Katiyar 《Journal of Materials Science》2007,42(17):7423-7432
The nanocrystalline fine powders (∼80 nm) of (Ba1−x
La
x
)(Fe2/3W1/3)1−x/4O3, (BLFW) (x = 0.0, 0.05, 0.10 and 0.15) were synthesized with a combined mechanical activation and conventional high-temperature solid-state
reaction methods. Preliminary X-ray structural analysis of pellet samples (prepared from fine powders) showed formation of
a single-phase tetragonal system. Detailed studies of dielectric properties (εr and tan δ) exhibit that these parameters are strongly dependent on frequency, temperature and La composition. The La-substitution
increases the dielectric constant and decreases the tan δ up to 10% substitutions of La at the Ba-site, and then reversed
the variation, and hence this composition is considered as a critical composition. This observation was found valid for structure,
microstructures, dielectric constant, electrical conductivity, J–E characteristics and impedance parameters also. Like in other perovskites (PZT, BZT), La substitution plays an important role
in tailoring the properties of Ba(Fe2/3W1/3)O3 ceramics. 相似文献
18.
Lead-free ferroelectric ceramics of (1−x) [0.88Na0.5Bi0.5TiO3-0.12K0.5Bi0.5TiO3]-x KNbO3(x = 0, 0.02, 0.04, and 0.06) were prepared by the conventional ceramic fabrication technique. The crystal structure, dielectric properties and P-E hysteresis loops were investigated. XRD data showed that all compositions could form pure perovskite structure. Temperature dependence of dielectric constant ε r and dissipation factor tanδ measurement between room temperature and 500∘C revealed that the compounds experience phase transitions that from ferroelectric to anti-ferroelectric and anti-ferroelectric to paraelectric in the range of x = 0–0.04. The frequency dependent dielectric constant showed these compounds were relaxor ferroelectric. At low frequency and high temperature, dielectric constant and dissipation factor increased sharply attributed to the superparaelectric clusters after the KNbO3 doped. 相似文献
19.
Xin Huang Huaiwu Zhang Jie Li Yuanming Lai 《Journal of Materials Science: Materials in Electronics》2016,27(11):11241-11247
The effects of La3+ doped in calcium copper titanate (CCTO) at Ca2+ site and Cu2+ site were examined. The doped compositions, La0.1Ca0.85Cu3Ti4O12 (LCCTO) ceramics and CaLa0.1Cu2.85Ti4O12 (CLCTO) ceramics were prepared by the solid-state method. The microstructure, dielectric properties, complex impedance and nonlinear I–V characteristics were studied. And it was found that La3+ doped at Ca2+ site achieved lower sintering temperatures than that doped at Cu2+ site in CCTO ceramics. The dielectric loss (tan δ) of LCCTO ceramics was about 0.05 at 40 kHz when the sample was sintered at 1080 °C. Dielectric constant (ε′) of LCCTO ceramics was about 3.2 × 104 when the sample was sintered at 1100 °C, which was larger than CLCTO ceramics examined under the same process condition with sintering temperatures vary. The impedance analysis revealed that LCCTO ceramics had an influence of resistance of grain boundaries, which was stronger than that of CLCTO ceramics. Meanwhile, both LCCTO ceramics and CLCTO ceramics had a nonlinear-Ohmic property. 相似文献
20.
Yuanliang Li Wenxin Dun Shuhao Yan Guifu Zuo Yuanfang Qu Zhongqiu Li 《Journal of Materials Science: Materials in Electronics》2017,28(16):11636-11643
The BaZr0.2Ti0.8O3 ceramics with perovskite structure were prepared by solid state reaction method with addition of x La2O3 and x La2O3?+?0.2 wt% Sm2O3 (x?=?0.0, 0.1 and 0.4 wt%). Microstructure and dielectric behaviour of the obtained ceramics were respectively investigated. The compositions of these ceramics demonstrated a single-phase cubic symmetry in a room-temperature X-ray diffraction study. The dielectric constant peak of those samples with addition of x La2O3 and x La2O3?+?0.2 wt% Sm2O3 greatly reduced along with increasing x. Simultaneously, a drastic increase of the values of γ was also observed when x rose, exhibiting a diffuse phase transition. T m increased along with increasing La content for x La2O3 doped BZT20 ceramics, but decreased along with increasing La content for x La2O3?+?0.2 wt% Sm2O3 doped BZT20 ceramics. Owing to the doping of Sm3+, the x La2O3?+?0.2 wt% Sm2O3 doped BZT20 ceramics have maintained very low and stable dissipation factors under an increasing environment temperature, making them superior candidates for applications. 相似文献