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1.
The influence of sintering conditions on the microstructural features and impedance characteristics of the giant dielectric
constant material CaCu3Ti4O12 (CCTO) was investigated. The microstructure and impedance characteristics were found to be strongly dependent on the sintering
conditions. Sintering of the CCTO ceramics at elevated temperatures (>1100 °C) for prolonged durations resulted in the segregation
of Cu-rich phase, mostly confined to the surface, which was in concomitance with the appearance of the additional semicircle
at the low frequency end in Impedance (Z*) plots. The absence of this additional semicircle in the Cu-deficient CCTO ceramics
and the appearance of the same in Cu-rich CCTO ceramics that were deliberately fabricated corroborated the above observations.
Also, La2/3Cu3Ti4O12 (LCTO), a low dielectric constant member of CCTO family, which consisted of small grains without the segregation of Cu-rich
phase at the grain boundary, did not reveal the presence of additional semicircle in the Z*plots. 相似文献
2.
P. Thomas L. N. Sathapathy K. Dwarakanath K. B. R. Varma 《Bulletin of Materials Science》2007,30(6):567-570
CaCu3Ti4O12 (CCTO) was synthesized and sintered by microwave processing at 2·45 GHz, 1·1 kW. The optimum calcination temperature using
microwave heating was determined to be 950°C for 20 min to obtain cubic CCTO powders. The microwave processed powders were
sintered to 94% density at 1000°C/60 min. The microstructural studies carried out on these ceramics revealed the grain size
to be in the range 1–7 μm. The dielectric constants for the microwave sintered (1000°C/60 min) ceramics were found to vary
from 11000–7700 in the 100 Hz–00 kHz frequency range. Interestingly the dielectric loss had lower values than those sintered
by conventional sintering routes and decreases with increase in frequency. 相似文献
3.
CaCu3Ti4O12 (CCTO) thin film was successfully deposited on boron doped silica substrate by chemical solution deposition and rapid thermal
processing. The phase and microstructure of the deposited films were studied as a function of sintering temperature, employing
X-ray diffractometry and scanning electron microscopy. Dielectric properties of the films were measured at room temperature
using impedance spectroscopy. Polycrystalline pure phase CCTO thin films with (220) preferential orientation was obtained
at a sintering temperature of 750°C. There was a bimodal size distribution of grains. The dielectric constant and loss factor
at 1 kHz obtained for a film sintered at 750°C was k ∼ 2000 and tan δ ∼ 0.05. 相似文献
4.
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
5.
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
6.
L. F. Xu T. Cheng R. L. Wang H. B. Xiao G. Z. Liu C. P. Yang 《Journal of Materials Science: Materials in Electronics》2014,25(2):817-823
Influence of bismuth substitution on calcium site in CaCu3Ti4O12 has been investigated. Compositions of Ca1-3/2xBixCu3Ti4O12 (x = 0, 0.05, 0.10, 0.15 and 0.20) were fabricated by solid-state sintering method. Crystal structure is remained cubic. X-ray diffraction indicates the presence of secondary phase of CuO in CCTO ceramics. Bismuth doping restrains the formation of CuO phase apparently. The grain size of CaCu3Ti4O12 ceramics was greatly decreased by Bi3+ doping, resulting from the ability of bismuth to inhibit the grain growth. The dielectric and electric properties of CCTO ceramics were found to be influenced by bismuth doping. The fitting results of the complex impedance spectra showed an increase of the resistance of grain and grain boundary by bismuth substitution. Ca0.70Bi0.20Cu3Ti4O12 showed the highest dielectric constant in the low frequency range. A modest composition such as Ca0.85Bi0.10Cu3Ti4O12 expressed the optimized dielectric properties of higher dielectric constant (1.3 × 104) and lower dielectric loss (0.06) than pure CCTO. The low and high temperature dielectric loss spectra demonstrate the interfacial polarization of the initial and secondary oxygen ionization, relating with the grain and grain boundary (the electrode contact for Ca0.70Bi0.20Cu3Ti4O12) respectively. 相似文献
7.
Suman Rani Neetu Ahlawat Kanta Maan Sangwan Sunita Rani R. Punia Jaideep Malik 《Journal of Materials Science: Materials in Electronics》2018,29(13):10825-10833
High performance dielectric materials are highly required for practical application for energy storage technologies. In this work, high-k pristine and modified calcium copper titanate having nominal formula Ca0.95Nd0.05Cu3Ti4?xZrxO12 (x?=?0.01, 0.03 & 0.10) were synthesized and characterized for structural and dielectric properties. Single phase formation of the synthesized compositions was confirmed by X-ray diffraction patterns and further analysed using Rietveld refinement technique. Phase purity of the synthesized ceramics was further confirmed by Energy-dispersive X-ray Spectroscopy (EDX) analysis. SEM images demonstrated that grain size of the modified CCTO ceramics was controlled by Zr4+ ions due to solute drag effect. Impedance spectroscopy was employed to understand the grain, grain boundaries and electrode contribution to the dielectric response. Nyquist plots were fitted with a 2R-CPE model which confirms the non-ideality of the system. Substitution of specific concentration of Nd and Zr improved the dielectric properties of high dielectric permittivity (ε′ ~?16,902) and minimal tanδ (≤?0.10) over a wide frequency range. The giant ε′ of the investigated system was attributed to internal barrier layer capacitance (IBLC) effect and reduced tanδ accredited to enhanced grain boundaries resistance due to substitution of Zr4+ ions at Ti4+ site. 相似文献
8.
Alok Kumar Rai N. K. Singh Sang-Kwon Lee K. D. Mandal D. Kumar Om Parkash 《Journal of Materials Science: Materials in Electronics》2011,22(9):1286-1289
Dielectric properties of iron doped CaCu3Ti4O12 (CCTO), viz. CaCu3Ti3.9Fe0.1O12 (CCTFO) prepared by a novel semi-wet route have been investigated. X-ray diffraction of powder sintered at 900 °C show formation
of single phase solid solution. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of CuO rich phase at grain
boundaries of CCTFO. Nature of dielectric relaxation observed above room temperature is studied using complex plane impedance
analysis and modulus spectroscopy. It has been found that out of the two relaxations reported earlier above room temperature,
one occurring at lower temperature is due to grainboundaries interfacial polarization. 相似文献
9.
Yang Wu Ruzhong Zuo Jinjin Zhang Yuanyuan Zhou Zhenxing Yue 《Journal of Materials Science: Materials in Electronics》2011,22(2):106-110
The effect of CuO and B2O3 co-doping on the sintering behavior, microstructure and microwave dielectric properties of tungsten bronze type Ba4Nd9.3Ti18O54 (BNT) ceramics has been investigated by means of a traditional solid-state mixed oxide route. On the one hand, it was indicated
that the mixture of CuO and B2O3 is an effective sintering aid for BNT matrix compositions owing to the existence of a low-temperature eutectic reaction.
On the other hand, it was found that the addition of CuO and B2O3 has an obvious effect on microwave dielectric properties of BNT ceramics, depending on the amount of sintering aids, the
sample density and microstructure. The liquid phases from sintering aids can promote densification, but simultaneously induce
grain growth which tends to decrease the sintering driving force. BNT ceramics doped with 3 wt% CuO–B2O3 mixture can be well sintered at 950°C for 4 h and still exhibit relatively good microwave dielectric properties. 相似文献
10.
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
11.
Xiuli Chen Huanfu Zhou Liang Fang Dongjin Chu Changda Li Ruili Guo Hong Wang 《Journal of Materials Science: Materials in Electronics》2011,22(4):371-375
The influences of B2O3 and CuO (BCu, B2O3: CuO = 1:1) additions on the sintering behavior and microwave dielectric properties of LiNb0.6Ti0.5O3 (LNT) ceramics were investigated. LNT ceramics were prepared with conventional solid-state method and sintered at temperatures
about 1,100 °C. The sintering temperature of LNT ceramics with BCu addition could be effectively reduced to 900 °C due to
the liquid phase effects resulting from the additives. The addition of BCu does not induce much degradation in the microwave
dielectric properties. Typically, the excellent microwave dielectric properties of εr = 66, Q × f = 6,210 GHz, and τ
f
= 25 ppm/oC were obtained for the 2 wt% BCu-doped sample sintered at 900 °C. Chemical compatibility of silver electrodes and low-fired
samples has also been investigated. 相似文献
12.
Ekaphan Swatsitang Krissana Prompa Thanin Putjuso 《Journal of Materials Science: Materials in Electronics》2018,29(15):12639-12651
In this work, the nominal CaCu3?xMgxTi4.2O12 (0.00, 0.05 and 0.10) ceramics were prepared by sintering pellets of their precursor powders obtained by a polymer pyrolysis solution method at 1100 °C for different sintering time of 8 and 12 h. Very low loss tangent (tanδ)?<?0.009–0.014 and giant dielectric constant (ε′) ~?1.1?×?104–1.8?×?104 with excellent temperature coefficient (Δε′) less than ±?15% in a temperature range of ??60 to 210 °C were achieved. These excellent performances suggested a potent application of the ceramics for high temperature X8R and X9R capacitors. It was found that tanδ values decreased with increasing Mg2+ dopants due to the increase of grain boundary resistance (Rgb) caused by the very high density of grain, resulting from the substitution of small ionic radius Mg2+ dopants in the structure. In addition, CaCu3?xMgxTi4.2O12 ceramics displayed non-linear characteristics with the significant enhancements of a non-linear coefficient (α) and a breakdown field (Eb) due to Mg2+doping. The high values of ε′ (14012), α (13.64) and Eb (5977.02 V/cm) with very low tanδ value (0.009) were obtained in a CaCu2.90Mg0.10Ti4.2O12 ceramic sintered at 1100 °C for 8 h. 相似文献
13.
H. L. Pan M. T. Liu M. F. Li F. Ling H. T. Wu 《Journal of Materials Science: Materials in Electronics》2018,29(2):999-1003
Li6Mg7Ti3O16 ceramics were prepared by the conventional solid-state method with 1–5 wt% LiF as the sintering aid. Effects of LiF additions on the phase compositions, sintering characteristics, micro-structures and microwave dielectric properties of Li6Mg7Ti3O16 ceramics were investigated. The LiF addition could effectively lower the sintering temperature of Li6Mg7Ti3O16 ceramics from 1550 to 900 °C. For different LiF-doped compositions, the optimum dielectric permittivity (ε r ) and quality factor (Q·f) values first increased and then decreased with the increase of LiF contents, whereas the temperature coefficient of resonant frequency (τ f ) fluctuated between ??14.39 and ??8.21 ppm/°C. Typically, Li6Mg7Ti3O16 ceramics with 4 wt% LiF sintered at 900 °C exhibited excellent microwave dielectric properties of ε r ?=?16.17, Q·f?=?80,921 GHz and τ f ?=???8.21 ppm/°C, which are promising materials for the low temperature co-fired ceramics applications. 相似文献
14.
C. R. Foschini R. Tararam A. Z. Simões L. S. Rocha C. O. P. Santos E. Longo J. A. Varela 《Journal of Materials Science: Materials in Electronics》2016,27(3):2175-2182
Calcium copper titanate, CaCu3Ti4O12, CCTO, thin films with polycrystalline nature have been deposited by RF sputtering on Pt/Ti/SiO2/Si (100) substrates at a room temperature followed by annealing at 600 °C for 2 h in a conventional furnace. The crystalline structure and the surface morphology of the films were markedly affected by the growth conditions. Rietveld analysis reveal a CCTO film with 100 % pure perovskite belonging to a space group Im3 and pseudo-cubic structure. The XPS spectroscopy reveal that the in a reducing N2 atmosphere a lower Cu/Ca and Ti/Ca ratio were detected, while the O2 treatment led to an excess of Cu, due to Cu segregation of the surface forming copper oxide crystals. The film present frequency -independent dielectric properties in the temperature range evaluated, which is similar to those properties obtained in single-crystal or epitaxial thin films. The room temperature dielectric constant of the 600-nm-thick CCTO films annealed at 600 °C at 1 kHz was found to be 70. The leakage current of the MFS capacitor structure was governed by the Schottky barrier conduction mechanism and the leakage current density was lower than 10?7 A/cm2 at a 1.0 V. The current–voltage measurements on MFS capacitors established good switching characteristics. 相似文献
15.
Zhanqing Liu Zupei Yang Xiaolian Chao 《Journal of Materials Science: Materials in Electronics》2016,27(9):8980-8990
La2/3Cu3Ti4O12 (LCTO) precursor powders were synthesized by the sol–gel method. Effect of sol conditions and sintering process on microstructure and dielectric properties of LCTO powders or ceramics were investigated systematically. The optimum sol conditions for the synthesis of precursor powders were as follows: the Ti4+ concentration of 1.00 mol/L, the molar ratio of water and titanium of 5.6:1 and the sol pH of 1.0, respectively. After sintered at 1105 °C for 15 h, the LCTO ceramics exhibited more homogeneous microstructure, much higher dielectric constant (ca 09–1.6 × 104) and lower dielectric loss (ca 0.057). The higher dielectric constant of the LCTO ceramics might be due to the internal barrier layer capacitor effect. The LCTO ceramics showed two kinds of conductivity activation energy for grain boundary conductivity from complex impedance analysis. The transition temperature of two activation energy values occured between 170 and 210 °C. The temperature range of 170–210 °C was critical pseudocritical region of the dielectric constant, dielectric loss and activation energy. Furthermore, it was concluded that the grain boundary play an important role for electrical properties. 相似文献
16.
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
17.
Hong-Tie Soong Cheng-Hsing Hsu Cheng-Liang Huang Ming-Ta Kuo 《Journal of Materials Science》2007,42(7):2393-2398
The microwave dielectric properties and the microstructures of Sm(Co1/2Ti1/2)O3 ceramics with B2O3 additions (0.25 and 0.5 wt%) prepared by conventional solid-state route have been investigated. The prepared Sm(Co1/2Ti1/2)O3 exhibited a mixture of Co and Ti showing 1:1 order in the B-site. Doping with B2O3 (up to 0.5 wt%) can effectively promote the densification of Sm(Co1/2Ti1/2)O3 ceramics with low sintering temperature. It is found that Sm(Co1/2Ti1/2)O3 ceramics can be sintered at 1,260 °C due to the grain boundary phase effect of B2O3 addition. At 1,290 °C, Sm(Co1/2Ti1/2)O3 ceramics with 0.5 wt% B2O3 addition possess a dielectric constant (ε
r) of 27.7, a Q × f value of 33,600 (at 9 GHz) and a temperature coefficient of resonant frequency (τf) of −11.4 ppm/ °C. The B2O3-doped Sm(Co1/2Ti1/2)O3 ceramics can find applications in microwave devices requiring low sintering temperature. 相似文献
18.
Z. C. Li G. H. Chen C. L. Yuan C. R. Zhou T. Yang Y. Yang 《Journal of Materials Science: Materials in Electronics》2017,28(2):1151-1158
Sr0.97La0.02TiO3 ceramics with samll amounts of NiNb2O6 additives were prepared by the traditional solid state sintering method, and the phase purity, microstructure, dielectric properties and energy storage behavior of the NiNb2O6-added Sr0.97La0.02TiO3 ceramics were investigated. The results show that the grain size of the ceramics firstly decreases and then increases with increasing NiNb2O6 concentration. The average grain size reaches 0.55 um for the sample with 4.5 wt% NiNb2O6. Moreover, impedance spectroscopy (IS) analysis was employed to study the electrical conductive behavior of NiNb2O6-doped Sr0.97La0.02TiO3 ceramics. IS results reveale that the NiNb2O6-doped Sr0.97La0.02TiO3 ceramic has large R gb /(R gb + R g ) ratios due to the decreased grain sizes. The breakdown strength is notably improved, and the highest breakdown strength of 324 kV/cm can be achieved for the sample with 4.5 wt% NiNb2O6 additive. The Sr0.97La0.02TiO3 sample with 4.5 wt% NiNb2O6 possesses the maximum theoretical energy density of 1.36 J/cm3, which is about 2 times higher than that of pure SrTiO3 in the literature. And its energy storage efficiency reaches 91.4 % under applied electric field of 80 kV/cm. This study provides the NiNb2O6 added ceramic as an attractive candidate for making high-energy density capacitors. 相似文献
19.
B. Shri Prakash K. B. R. Varma 《Journal of Materials Science: Materials in Electronics》2006,17(11):899-907
The effect of La3+ doping on Ca2+ sites in CaCu3Ti4O12 (CCTO) was examined. Polycrystalline samples in the chemical formula Ca(1-x)La(2/3)x
Cu3Ti4O12 with x = 0, 0.5, 1 were synthesized via the conventional solid state reaction route. X-ray powder diffraction analysis confirmed
the formation of the monophasic compounds and indicated the structure to be remaining cubic with a small increase in lattice
parameter with increase in La3+ doping. The dielectric and impedance characteristics of Ca(1-x)La(2/3)x
Cu3Ti4O12 were studied in the 100 Hz–10 MHz frequency range at various temperatures (100–475 K). A remarkable decrease in grain size
from 50 μm to 3–5 μm was observed on La3+ substitution. The dielectric constant of CaCu3Ti4O12 decreased drastically on La3+ doping. The frequency and temperature responses of dielectric constant of La3+ doped samples were found to be similar to that of CaCu3Ti4O12. The effects of La3+ doping on the electrical properties of CaCu3Ti4O12 were probed using impedance spectroscopy. The conducting properties of grain decreased while that of the grain boundary increased
on La3+ doping, resulting in a decrease of the internal barrier layer effect. A decrease in grain boundary capacitance and stable
grain response in La3+ doped CCTO ceramics were unambiguously established by modulus spectra studies. 相似文献
20.
Weeraya Somphan Nuchjarin Sangwong Teerapon Yamwong Prasit Thongbai 《Journal of Materials Science: Materials in Electronics》2012,23(6):1229-1234
The electrical properties and dielectric response in Na1/2Y1/2Cu3Ti4O12 ceramic prepared by conventional solid-state reaction method and sintered at 1,090 °C for 5 h were investigated as functions
of frequency and temperature. Main phase of Na1/2Y1/2Cu3Ti4O12 with CaCu3Ti4O12-like crystallographic structure and CuO secondary phase were observed in the X-ray diffraction pattern. Abnormal grain growth
was observed just as observed in CaCu3Ti4O12 ceramics. The Na1/2Y1/2Cu3Ti4O12 ceramic exhibits a high ε′ of ~2.04 × 104 at 20 °C and 1 kHz and low tan δ (with the minimum 0.080 at 5 kHz). Impedance spectroscopy analysis reveals that Na1/2Y1/2Cu3Ti4O12 ceramic is electrically heterogeneous, consisting of semiconducting grains and insulating grain boundaries. Giant ε′ response
in Na1/2Y1/2Cu3Ti4O12 ceramic is therefore attributed to an internal barrier layer capacitor effect. 相似文献