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1.
Composite ceramics of Ba0.6Sr0.4TiO3 + 60 wt.% MgO were prepared from fine constituent powders by sintering at 1200–1280 °C. The composite specimens sintered at the relatively low temperatures showed satisfactory densification due to fine morphology of the constituent powders. The elevation of sintering temperature promoted the incorporation of Mg2+ into the lattice of the Ba0.6Sr0.4TiO3 phase and grain growth of the two constituent phases. The dependence of the dielectric properties on sintering temperature was explained in relation to the structural evolution. Controlling the sintering temperature of the composite was found to be important to achieve the desired nonlinear dielectric properties. Sintering at 1230 °C was determined to be preferred for the composite in terms of the nonlinear dielectric properties. The specimen sintered at the temperature attained a tunability of 17.3% and a figure of merit of 127 at 10 kHz and 20 kV/cm. 相似文献
2.
Feng Ni Laihui Luo Xiaoyin Pan Yuepin Zhang Hongbing Chen 《Journal of Materials Science》2012,47(7):3354-3360
Lead-free piezoelectric ceramics (1 − x)Bi0.5(Na0.84K0.16)0.5TiO3–xBa0.77Ca0.23TiO3 (BNKT–xBCT, x = 0–0.04) were synthesized by conventional solid-state reaction method. The piezoelectric, dielectric, and ferroelectric
characteristics of the ceramics are investigated and discussed. The XRD results show that Ba0.77Ca0.23TiO3 (BCT) has diffused into Bi0.5(Na0.84K0.16)0.5TiO3 (BNKT) lattices to form a new solid solution. It is shown that moderate additive of BCT (x ≤ 0.025) in BNKT–xBCT ceramics can enhance their piezoelectric and ferroelectric properties. Three dielectric anomalies are observed in BNKT–xBCT (x ≤ 0.03) ceramics. The piezoelectric measurements and P–E hysteresis loops reveal that BNKT–0.025BCT ceramic has the highest piezoelectric performance and strongest ferroelectricity
in all the samples. Piezoelectric constants d
33, k
p, and k
t of 175 pC/N, 29.1, and 54% are, respectively, achieved. Remnant polarization P
r and coercive field E
c reach 28.3 μC/cm2 and 24.2 kV/cm, respectively. 相似文献
3.
Dielectric tunable properties of Ba0.5Sr0.5TiO3–MgMoO4 composite ceramics for microwave applications
Linjiang Tang Jinwen Wang Jiwei Zhai Bo Shen Xi Yao 《Journal of Materials Science: Materials in Electronics》2013,24(7):2576-2580
(1?x) Ba0.5Sr0.5TiO3–xMgMoO4 (x = 0, 5, 10, 20 and 30 wt%) composite ceramics were prepared via solid state reaction processing. Their structure and dielectric properties were systematically characterized. The introduction of MgMoO4 resulted in a change in lattice constant of the perovskite phase and partial reaction between MgMoO4 and Ba0.5Sr0.5TiO3 occurred in the sintering process. Both X-Ray Diffraction (XRD) and Back-scattered Electron Images (BEI) analysis show the co-existence of three phase structures of BST, MgMoO4 and BaMoO4. With increasing of MgMoO4 content, the tunability of the composite ceramics was decreased due to the increase of the amount of non-ferroelectric phases. The Curie temperature Tc of the samples gradually shifted to low temperatures with increasing of MgMoO4 content. Dielectric constant can be adjusted in the range from 2035 to 150, meanwhile maintain a relatively high tunability and Q values. The sample with 20 wt% MgMoO4 possesses a tunability of 10 %, a low dielectric constant of 111 and an appropriate Q value of 183 (2.240 GHz), which meet the requirements of high power and impedance matching, thus making it a promising candidate for applications as electrically tunable microwave devices. 相似文献
4.
Changrong Zhou Xinyu Liu Weizhou Li Changlai Yuan Guohua Chen 《Journal of Materials Science》2009,44(14):3833-3840
Lead-free piezoelectric ceramics (1 − x − y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiCoO3 (x = 0.12–0.24, y = 0–0.04) have been fabricated by a conventional solid-state reaction method, and their structure and electrical properties
have been investigated. The XRD analysis shows that samples with y ≤ 0.03 exhibit a pure perovskite phase and very weak impurity reflections can be detected in the sample with y = 0.04. With x increasing from 0.12 to 0.24 and y increasing from 0 to 0.04, the ceramics transform gradually from a rhombohedral phase to a tetragonal phase and rhombohedral–tetragonal
phase coexistence to a pseudocubic phase, respectively. The morphotropic phase boundary (MPB) of the system between rhombohedral
and tetragonal locates in the range of x = 0.18–0.21, y = 0–0.03. The ceramics near the composition of the MPB have good performances with piezoelectric constant d
33 = 156 pC/N and electromechanical coupling factor k
p = 0.34 at x = 0.21 and y = 0.01, which attains a maximum value in this ternary system. Adding content of BiCoO3 leads to a disappearance of the response in the curves of dielectric constant-temperature to the ferroelectric–antiferroelectric
transition. The temperature dependence of dielectric properties suggests that the ceramics are relaxor ferroelectrics. The
results show that (1 − x − y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiCoO3 ceramics are good candidate for use as lead-free ceramics. 相似文献
5.
Composite ceramics of (1 ? x)Ba4LiNb3O12–xBaWO4 (x = 0.36–0.69) had been synthesized by co-firing the mixtures of Ba4LiNb3O12 and BaWO4 powders. The structures and microwave dielectric properties of the ceramics were studied by XRD, SEM, and TEM. These ceramics consisted of hexagonal Ba4LiNb3O12 and tetragonal BaWO4. The two phases co-existed well in the ceramics, and there was not obvious reaction at interfacial areas among grains. These ceramics had low sintering temperatures and excellent microwave dielectric properties, especially the small temperature coefficients of resonant frequency (τf) and high quality factor (Q × f) values. For composition at x = 0.69, the ceramic sintered at 1070 °C had Q × f value of 75,500 GHz and τf value of +8.7 ppm/°C. 相似文献
6.
Yebin Xu Chao Lv Yanyan He Jingyuan Zhao Changnian Li Buyin Li 《Journal of Materials Science: Materials in Electronics》2013,24(11):4161-4165
Mn-doped Ba0.5Sr0.5TiO3–MgO–Mg2SiO4 composite ceramics were prepared by a solid-state reaction method, and the dielectric tunable properties were investigated. It was observed that the composite ceramics show three crystalline phases: Ba0.5Sr0.5TiO3, MgO and Mg2SiO4 phases. Mn doping significantly improves the dielectric tunable properties of Ba0.5Sr0.5TiO3–MgO–Mg2SiO4 composite ceramics. Mn-doped Ba0.5Sr0.5TiO3–MgO–Mg2SiO4 composites have dielectric constant of 114.2–127.0, and tunability of 11.3–13.0 % at 10 kHz under 3 kV/mm, indicating that they are promising candidate materials for tunable microwave applications requiring a low dielectric constant. 相似文献
7.
0.09(Bi0.5Na0.5)0.94Ba0.06TiO3–(0.01 − x) Bi0.5(Na0.82K0.18)0.5TiO3–x BiAlO3 (BNBKT–xBA) lead-free piezoelectric ceramics were synthesized by conventional solid-state reaction processes. Structure, ferroelectric and piezoelectric properties of BNBKT–xBA ceramics were investigated. X-ray diffraction data shows that BNBKT–xBA ceramics form the pure perovskite phases and the ceramics have the morphotropic phase boundary when x ≤ 0.030. At room temperature, the BNBKT–xBA ceramics at x = 0.030 have better electrical properties, the piezoelectric constant d33 and planar coupling factor kp of BNBKT–xBA ceramics reaches peak values at x = 0.030: d33 = 217 pC N−1, kp = 0.308. The remnant polarization Pr, mechanical quality factor Qm and relative dielectric constant ?r of BNBKT–xBA ceramics at x = 0.030 attains 33.8 μC cm−2, 133 and 928 (100 KHz), respectively. As BA content increase, the depolarization temperature Td shift toward lower temperature, and Td of BNBKT–xBA ceramics with x = 0.030 decreased to 55 °C. 相似文献
8.
Yingxiang Li Junshan Li Bin Tang Shuren Zhang Hao Li Zhenjun Qin Hetuo Chen Han Yang Hong Tu 《Journal of Materials Science: Materials in Electronics》2014,25(6):2780-2785
The effects of CaO–B2O3–SiO2 (CBS) glass addition on the sintering temperature and dielectric properties of Li2ZnTi3O8–TiO2 (LZT) composite ceramics have been investigated. Due to the compensating effect of rutile TiO2 (τf ≈ +450 ppm/ °C), the temperature coefficient of resonant frequency (τf) for Li2ZnTi3O8 + 4 wt% TiO2 with biphasic structure was adjusted to a value near zero. The pure LZT ceramics were usually sintered at high temperature of about 1,160 °C. It was found in our experiment that a small amount of CBS glass additives could effectively lower the sintering temperature of LZT ceramics to 900 °C. With increasing the content of CBS glass, both of dielectric constant (εr) and quality factor (Q × f) value decreased. Typically, the 1 wt% CBS glass added Li2ZnTi3O8 + 4 wt% TiO2 ceramic sintered at 900 °C for 4 h exhibited good microwave dielectric properties of εr = 26.9, Q × f = 23,563 GHz and τf = ?1.5 ppm/ °C, which made it promising for low temperature co-fired ceramics technology application. 相似文献
9.
Min Xu Feifei Wang Tao Wang Xinman Chen Yanxue Tang Wangzhou Shi 《Journal of Materials Science》2011,46(13):4675-4682
In this study, the phase diagram and electric properties were demonstrated for a (Mn, K)-modified Bi0.5Na0.5TiO3 (BNT)-based solid solution. (0.935−x) Bi0.5Na0.5TiO3−xBi0.5K0.5TiO3−0.065BaTiO3 with 0.5% mol Mn doping was prepared by a conventional solid-state reaction method. A morphotropic phase boundary (MPB) formed
between the ferroelectric rhombohedral and tetragonal phases around x of 0.04 with the MPB tolerance factor t of 0.984–0.986. The temperature and composition dependence of the dielectric, piezoelectric, ferroelectric properties along
with the strain characteristics were investigated in detail and a phase diagram was presented. Around the MPB region, the
maximum values of piezoelectric constant d33* d_{33}^{*} of 290 pC/N, d
33 of 155 pC/N, dielectric constant e33T /e0 \varepsilon_{33}^{T} /\varepsilon_{0} of 1059 and low dielectric loss tangent tan δ of 0.017 were obtained. In addition, the authors also suggest that the solid
solution with composition x of 0.24, exhibiting both high-depolarization temperature T
d of 182 °C, d33* d_{33}^{*} of 156 pC/N, d
33 of 130 pC/N, will be favorable for high-temperature actuator and sensor applications. 相似文献
10.
Bo Zhang Qing Zhao Aimin Chang Haixue Yan Yiquan Wu 《Journal of Materials Science: Materials in Electronics》2013,24(11):4452-4456
New negative temperature coefficient (NTC) ceramics based on xMgAl2O4–(1 ? x)LaCr0.5Mn0.5O3 (x = 0, 0.4, 0.6, 0.8) composition were investigated. The composite ceramics (x = 0.4, 0.6, 0.8) consisted of two phases: a cubic spinel MgAl2O4 phase and an orthorhombic perovskite LaCr0.5Mn0.5O3 phase isomorphic to LaCrO3. The brighter regions were the LaCr0.5Mn0.5O3 and the darker was the MgAl2O4. There was ion diffusion between these two phases. X-ray photoelectron spectroscopy analysis corroborated the presence of Cr3+, Cr4+, Mn3+ and Mn4+ ions on lattice sites, which may result in the hopping conduction. The ρ 300 and B 400/800 constant increased with increasing MgAl2O4 content. The values of ρ 300, B 400/800 and activation energy of NTC thermistors were in the range 1.76–1.22 × 108 Ωcm, 2,646–8,711 K, 0.228–0.746 eV, respectively. This means the electrical properties can be adjusted to desired values, depending on the MgAl2O4 content. 相似文献
11.
12.
Minhong Jiang Xinyu Liu Guohua Chen Jun Cheng 《Journal of Materials Science: Materials in Electronics》2011,22(7):876-881
The piezoelectric properties of (1 − x)(0.95K0.5Na0.5NbO3–0.05LiSbO3)–x BiMnO3 (x = 0, 0.002, 0.004, 0.006, 0.008, 0.01) lead-free piezoelectric ceramics were investigated as a function of x. These ceramics were fabricated by conventional ceramics sintering processing. BiMnO3 (BM)-doping was found to increase the Curie temperature, T
c, from 370 °C at x = 0–380 °C at x = 0.002, and clearly increase the d
33, Q
m and k
p values, showing “hard” characteristic. The good piezoelectric and electromechanical properties of d
33 = 226pC/N, k
p = 40.8%, tan θ = 2.60% and T
c = 370 °C appear at x = 0.004. 相似文献
13.
Laijun Liu Meixia WuYanmin Huang Zhao YangLiang Fang Changzheng Hu 《Materials Chemistry and Physics》2011
Dielectric and conductivity measurements were carried out on the 0.95(K0.5Na0.5)NbO3–0.05BaTiO3 (KNN–5BT) ceramic both as a function of temperature (∼350–850 K) and frequency (40 Hz to 100 MHz). A high-temperature dielectric relaxation above Curie temperature (∼590 K) was observed and analyzed with the Cole–Cole function. Frequency dependent conductivity was analyzed with an augmented Jonscher relation and exhibited a universal conductivity behavior. The activation energy of dielectric relaxation was estimated to be 1.09 eV. It could be attributed to the thermal motion of double ionized oxygen vacancy or to the formation of defect dipoles between the acceptor ion and charge compensating oxygen vacancies. The mechanism for both the high-temperature dielectric relaxation and the frequency dependent conductivity was proposed based on a possible mode of incorporation of Ba2+ and Ti4+ ions into the KNN lattice sites. 相似文献
14.
15.
Dunmin Lin Chenggang Xu Qiaoji Zheng Yujun Wei Daojiang Gao 《Journal of Materials Science: Materials in Electronics》2009,20(5):393-397
(1 − x)Bi0.5Na0.5TiO3–xBi0.5Li0.5TiO3 lead-free ceramics have been prepared by a conventional solid-state reaction method, and their piezoelectric and dielectric
properties have been studied. X-ray diffraction studies reveal that Li+ diffuses into the Bi0.5Na0.5TiO3 lattices to form a solid solution with a pure perovskite structure. The addition of Bi0.5Li0.5TiO3 effectively lowers the sintering temperature of the ceramics and greatly assists in the densification of the ceramics. The
ceramic with x = 0.075 possesses the optimum piezoelectric properties: piezoelectric coefficient d
33 = 121 pC/N and planar electromechanical coupling factor k
P = 18.3%. After the partial substitution of Li+ for Na+ in the A-sites of Bi0.5Na0.5TiO3, the ceramics exhibit more relaxor characteristic, which is probably resulted from the cation disordering in the 12-fold
coordination sites. The depolarization temperature T
d shifts to low temperature with the substitution level x of Li+ for Na+ increasing. 相似文献
16.
The effect of B2O3 addition on the sintering, microstructure and the microwave dielectric properties of the 5Li2O–0.58Nb2O5–3.23TiO2 (LNT) ceramics have been investigated. It is found that the LNT ceramics could be sintered well at ∼880 °C with low-level doping of B2O3 (≤2 wt.%). Only Li2TiO3 solid solution (Li2TiO3ss) crystal structure could be detected for all the ceramics with various amounts of B2O3 addition from the X-ray diffraction (XRD) results. And interestingly, two phases with different color in SEM images are observed in B2O3-doped LNT ceramics. EDS results suggest that the two different phases are two Li2TiO3ss phases with different amount of Nb. In addition, there is no much degradation in the microwave dielectric properties with the B2O3 adding. In the case of 0.5 wt.% B2O3-doped samples sintered at 880 °C, good microwave dielectric properties of ?r = 22, Q × f = 32,000 GHz, τf = 9.5 ppm °C−1 are obtained. 相似文献
17.
18.
Shuping Gong Lianhua Li Mei Guo Gang Dou Binbin Chen Dongxiang Zhou 《Journal of Materials Science: Materials in Electronics》2012,23(7):1346-1351
The effects of CuO additive on sintering temperature and microwave dielectric properties of 7NiNb2O6–9TiO2 ceramics prepared by solid-state reaction method have been investigated. The phases and microstructure have also been evaluated using X-ray diffraction and scanning electron microscopy. The pure 7NiNb2O6–9TiO2 ceramics show a high sintering temperature of about 1,200?°C. However, the addition of CuO lowered the sintering temperature of 7NiNb2O6–9TiO2 ceramics from 1,200 to 935?°C due to the CuO liquid-phase. The results showed that the microwave dielectric properties were strongly dependent on densification, crystalline phases and grain size. The 7NiNb2O6–9TiO2 ceramics with the addition of 3.2 wt% CuO sintered at 935?°C afforded excellent dielectric properties of ε r ?=?60.5, Q?×?f?=?10,039?GHz (at 3.8?GHz) and τ f ?=?62?ppm/°C, which represented very promising candidates for LTCC dielectric materials. 相似文献
19.
A highly stable perovskite cathode material, Ba0.5Sr0.5(Co0.6Zr0.2)Fe0.2O3−δ (BSCZF) for intermediate temperature solid-oxide fuel cells (IT-SOFCs) was synthesized via the improved EDTA-citric acid complexing technique combined with high-temperature sintering. The product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectra (EIS) measurements. An electrolyte-supported BSCZF/SDC/Ni-SDC fuel cell was fabricated to evaluate the performance of the material. The XRD study indicates that the sintering temperature higher than 950 °C is sufficient to the formation of clean single BSCZF perovskite phase. Due to the incorporation of Zr ions, BSCZF perovskite exhibit lower electrical conductivity with higher activation energy but higher structural stability than the Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) parent oxide. The maximum electrical conductivity of BSCZF attains 16.9 S cm−1 at around 540 °C. Impedance spectra showed that the ASRs of BSCZF cathode on samaria doped ceria (Ce0.8Sm0.2O1.9, SDC) electrolyte are low but are still slightly larger than those of BSCF at similar conditions. The BSCZF/SDC/Ni-SDC cell exhibited a stable output with the maximum power densities of 30, 75, 139 and 241 mW cm−2 at 550, 600, 650 and 700 °C, respectively. Due to the high electrochemical performances as well as the excellent stability, BSCZF perovskite may be an attractive cathode material for IT-SOFCs. 相似文献
20.
Superfine powders (~100 nm) with compositions of (1 − x)(Bi0.5Na0.5)0.94Ba0.06TiO3 + xNb5+ (BNTBT6 + xNb) with x from 0 to 0.02 were synthesized by an improved citrate sol–gel method using Nb2O5 as Nb5+ source. The sintering behavior, microstructure, and various electrical properties of BNTBT6 + xNb ceramics were investigated. The results indicated that the addition of a small amount of Nb5+ has no remarkable effect on the crystal structure and grain morphology, but the electrical properties of the ceramics are
obviously influenced. The BNTBT6 + 0.005Nb compositions exhibit enhanced densification behavior and improved electrical properties
of a piezoelectric constant d
33 ~ 205 pC/N and a planar electromechanical coupling factor k
p ~ 33%. 相似文献