共查询到20条相似文献,搜索用时 15 毫秒
1.
Hong-fang ZhangSiu Wing Or Helen Lai Wa Chan 《Journal of Alloys and Compounds》2011,509(21):6311-6316
Fine-grained Pb(Zr0.53Ti0.47)O3-(Ni0.5Zn0.5)Fe2O4 (PZT-NZFO) magnetoelectric (ME) composite ceramics were fabricated by a modified hybrid process at a low sintering temperature of 900 °C. Well-controlled crystallized grain size and homogeneous microstructure with a good mixture of two phases were observed in the ceramics. The ceramics show coexistence of ferrimagnetic and ferroelectric phases with well-formed ferromagnetic and ferroelectric hysteresis loops at room temperature. A significant ME effect was observed with a ME coefficient of 0.537 V cm−1 Oe−1 in the vicinity of electromechanical resonance. In addition, high capacitance can be obtained at low frequency, and magnetic properties in the ceramics can be tailored by the grain size of the ferromagnetic particles in a simple and flexible way. 相似文献
2.
Lead-free piezoelectric ceramics Sr2−xCaxNaNb5O15 + y wt% MnO2have been prepared by the conventional solid state reaction method. Our results reveal that Ca2+and Mn ions have entered into the Sr2NaNb5O15 lattices to form a solid solution with tungsten-bronze structure. The substitution of Ca2+ induces a decrease in piezoelectric coefficient d33, electromechanical coupling factors kp and kt, while, the addition of Mn ions decreases the sintering temperature and effectively promotes the densification of the ceramics. The effect of substitution of Ca2+and Mn ions on the structure, electrical properties and diffused phase changing were investigated systematically. For the ceramic with x = 0.05 and y = 0.5, the piezoelectric, dielectric and ferroelectric properties become optimum, giving a piezoelectric coefficient d33 = 190 pC/N, electromechanical coupling factors kp = 13.4% and kt = 36.5%, ?r = 2123, loss tangent tan δ = 0.038, remanent polarization Pr = 4.76 μC/cm2, coercive field Ec = 12.68 kV/cm, and Curie temperature Tc = 260 °C. 相似文献
3.
J. Leitner M. Nev?ivaD. Sedmidubský P. Voňka 《Journal of Alloys and Compounds》2011,509(15):4940-4943
The heats of drop-solution in 3Na2O + 4MoO3 melt at 973 K and 1073 K for calcium and strontium carbonates, Bi2O3, Nb2O5 and several stoichiometric mixed oxides in CaO-Nb2O5, SrO-Nb2O5 and Bi2O3-Nb2O5 systems were measured using a Setaram Multi HTC-96 calorimeter. The values of enthalpy of formation from constituent binary oxides at 298 K, ΔoxH, were derived for the mixed oxides under investigation: ΔoxH(CaNb2O6) = −132.0 ± 23.8 kJ mol−1, ΔoxH(Ca2Nb2O7) = −208.0 ± 31.9 kJ mol−1, ΔoxH(SrNb2O6) = −167.9 ± 19.1 kJ mol−1, ΔoxH(Sr2Nb2O7) = −289.2 ± 37.5 kJ mol−1 and ΔoxH(BiNbO4) = −41.9 ± 11.1 kJ mol−1. Additionally, the values ΔoxH for other mixed oxides with different stoichiometries were estimated on the basis of these experimental results. 相似文献
4.
Yuan-Bin Chen 《Journal of Alloys and Compounds》2011,509(24):6884-6888
The effects of BaCu(B2O5) additives on the sintering temperature and microwave dielectric properties of (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics were investigated. The (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics were not able to be sintered below 1000 °C. However, when BaCu(B2O5) were added, they were sintered below 1000 °C and had the good microwave dielectric properties. It was suggested that a liquid phase with the composition of BaCu(B2O5) was formed during the sintering and assisted the densification of the (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics at low temperature. BaCu(B2O5) powders were produced and used to reduce the sintering temperature of the (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics. Good microwave dielectric properties of Q × f = 35,000 GHz, ?r = 18.5.0 and τf = −51 ppm/°C were obtained for the (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics containing 7 wt.% mol% BaCu(B2O5) sintered at 950 °C for 4 h. 相似文献
5.
Shouguo Huang 《Journal of Alloys and Compounds》2011,509(11):4348-4351
A glass based on Y2O3-BaO-SiO2-B2O3-Al2O3 (named YBA) has been investigated as sealant for planar solid oxide fuel cells (SOFCs). The YBA glass has been systematically characterized by differential thermal analysis, dilatometer, scanning electron microscopy, impedance analysis, and open circuit voltage to examine their suitability as sealant. The coefficient of thermal expansion of YBA is 11.64 × 10−6 K−1 between 323 and 873 K. The resistivity is 9.1 × 104 Ω cm at 800 °C. The glass sealant is found to be well adhered with other cell components, such as electrolytes and stainless steels, at an optimum sealing temperature of 800 °C. All measured results showed that the YBA glass appears to be a promising sealant for SOFCs. 相似文献
6.
Zupei Yang Lijuan ZhangXiaolian Chao Lirong XiongJie Liu 《Journal of Alloys and Compounds》2011,509(35):8716-8719
The Ca1−xSrxCu3Ti4O12 (CSCTO) giant dielectric ceramics were prepared by conventional solid-state method. X-ray diffraction patterns revealed that a small amount of Sr2+ (x < 0.2) had no obvious effect on the phase structure of the CSCTO ceramics, while with increasing the Sr2+ content, a second phase of SrTiO3 appeared. Electrical properties of CSCTO ceramics greatly depended on the Sr2+ content. The Ca0.9Sr0.1Cu3Ti4O12 ceramics exhibited a higher permittivity (71,153) and lower dielectric loss (0.022) when measured at 1 kHz at room temperature. The ceramics also performed good temperature stability in the temperature range from −50 °C to 100 °C at 1 kHz. By impedance spectroscopy analysis, all compounds were found to be electrically heterogeneous, showing semiconducting grains and insulating grain boundaries. The grain resistance was 1.28 Ω and the grain boundary resistance was 1.31 × 105 Ω. All the results indicated that the Ca0.9Sr0.1Cu3Ti4O12 ceramics were very promising materials with higher permittivity for practical applications. 相似文献
7.
Xiuli ChenHuanfu Zhou Liang FangXiaobin Liu Yiliang Wang 《Journal of Alloys and Compounds》2011,509(19):5829-5832
The effects of BaCu(B2O5) (BCB) additions on the sintering temperature and microwave dielectric properties of Li2MgTi3O8 ceramic have been investigated. The pure Li2MgTi3O8 ceramic shows a relative high sintering temperature (∼1000 °C) and good microwave dielectric properties as Q × f of 40,000 GHz, ?r of 27.2, τf of 2.6 ppm/°C. It was found that the addition of a small amount of BCB can effectively lower the sintering temperature of Li2MgTi3O8 ceramics from 1025 to 900 °C and induce no obvious degradation of the microwave dielectric properties. Typically, the 0.5 wt% BCB added Li2MgTi3O8 ceramic sintered at 900 °C for 2 h exhibited good microwave dielectric properties of Q × f = 36,200 GHz (f = 7.31 GHz), ?r = 26 and τf = −2 ppm/°C. Compatibility with Ag electrode indicates this material can be applied to low temperature-cofired ceramics (LTCC) devices. 相似文献
8.
Shujun LiLin Ge Haitao GuYifeng Zheng Han ChenLucun Guo 《Journal of Alloys and Compounds》2011,509(1):94-98
The effect of ZnO addition on the sinterability and ionic conductivity of Ce0.8Y0.2O1.9 is investigated. Ce0.8Y0.2O1.9 is prepared using an EDTA-citrate complexing method in order to further improve its electrical properties. Using a ZnO content over 1 mol %, the sinterability of Ce0.8Y0.2O1.9 is significantly improved by reducing the sintering temperature from 1500 to 1350 °C and a relative density of above 95% was achieved. The highest ionic conductivity of 0.0516 S cm−1 was obtained at 750 °C for (YDC)0.99(ZnO)0.01 sintered at 1350 °C. Pure YDC sintered at 1500 °C, on the other hand, yielded 0.0289 S cm−1. 相似文献
9.
The phases, microstructure and microwave dielectric properties of ZnTiNb2O8-xTiO2 composite ceramics with different weight percentages of BaCu(B2O5) additive prepared by solid-state reaction method have been investigated using the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results showed that the microwave dielectric properties were strongly dependent on densification, grain sizes and crystalline phases. The sintering temperature of ZnTiNb2O8 ceramics was reduced from 1250 °C to 950 °C by doping BaCu(B2O5) additive and the temperature coefficient of resonant frequency (τf) was adjusted from negative value of −52 ppm/°C to 0 ppm/°C by incorporating TiO2. Addition of 2 wt% BaCu(B2O5) in ZnTiNb2O8-xTiO2 (x = 0.8) ceramics sintered at 950 °C showed excellent dielectric properties of ?r = 38.89, Q × f = 14,500 GHz (f = 4.715 GHz) and τf = 0 ppm/°C, which represented very promising candidates as LTCC dielectrics for LTCC applications. 相似文献
10.
B. Gaković B. Radak C. Radu M. Zamfirescu M. Trtica S. Petrović J. Stašić P. Panjan I.N. Mihailescu 《Surface & coatings technology》2012
We studied surface modification of a double layer protective coating on steel induced by single fs laser pulse irradiation in ambient air. The outer alumina (Al2O3) layer, which protects against aggressive environments, was 1.7 μm thick and the titanium aluminum nitride (TiAlN) layer in contact with the steel surface had a thickness of 1.9 μm. The pulses (λ = 775 nm, τ = 200 fs) were generated by a Ti:sapphire laser source. The pulse energy was varied from 0.32 μJ to 50 μJ, corresponding to an incident laser fluence of 0.11 J cm− 2 to 16.47 J cm− 2. The surface damage threshold was found to be 0.20 J cm− 2 and the alumina layer removal was initiated at 0.56 J cm− 2. This selective ablation of alumina was possible in a wide range of fluences, up to the maximum applied, without ablating the TiAlN layer beneath. 相似文献
11.
Xian-Zhong XiongZhan-Guo Liu Jia-Hu Ouyang Xiao-Liang XiaJun Xiang Xiao-Ming Liu 《Journal of Alloys and Compounds》2011,509(33):8392-8397
The pyrochlore-type phases with the compositions of SmDy1−xMgxZr2O7−x/2 (0 ≤ x ≤ 0.20) have been prepared by pressureless-sintering method for the first time as possible solid electrolytes. The structure and electrical conductivity of SmDy1−xMgxZr2O7−x/2 ceramics have been studied by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy measurements. SmDy1−xMgxZr2O7−x/2 (x = 0, 0.05, 0.10) ceramics exhibit a single phase of pyrochlore-type structure, and SmDy1−xMgxZr2O7−x/2 (x = 0.15, 0.20) ceramics consist of pyrochlore phase and a small amount of the second phase magnesia. The total conductivity of SmDy1−xMgxZr2O7−x/2 ceramics obeys the Arrhenius relation, and the total conductivity of each composition increases with increasing temperature from 673 to 1173 K. SmDy1−xMgxZr2O7−x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1.0 × 10−4 to 1.0 atm at all test temperature levels. The highest total conductivity value is about 8 × 10−3 S cm−1 at 1173 K for SmDy1−xMgxZr2O7−x/2 ceramics. 相似文献
12.
Fancheng MengCheng Liu Fan ZhangZhongqing Tian Weijiu Huang 《Journal of Alloys and Compounds》2012,512(1):63-67
Alumina matrix composites containing 5 and 10 wt% of ZrO2 were sintered under 100 MPa pressure by spark plasma sintering process. Alumina powder with an average particle size of 600 nm and yttria-stabilized zirconia with 16 at% of Y2O3 and with a particle size of 40 nm were used as starting materials. The influence of ZrO2 content and sintering temperature on microstructures and mechanical properties of the composites were investigated. All samples could be fully densified at a temperature lower than 1400 °C. The microstructure analysis indicated that the alumina grains had no significant growth (alumina size controlled in submicron level 0.66-0.79 μm), indicating that the zirconia particles provided a hindering effect on the grain growth of alumina. Vickers hardness and fracture toughness of composites increased with increasing ZrO2 content, and the samples containing 10 wt% of ZrO2 had the highest Vickers hardness of 18 GPa (5 kg load) and fracture toughness of 5.1 MPa m1/2. 相似文献
13.
Hanju LeeYoungwoon Yoon Hyungkeun YooSul A Choi Kyoungchul KimYunjung Choi Harutyun MelikyanTakayuki Ishibashi Barry FriedmanKiejin Lee 《Journal of Alloys and Compounds》2011,509(39):9434-9440
The crystallization process of bismuth substituted yttrium iron garnet (BixY3−xFe5O12; x = 0, 1, 2) powder prepared by the metal-organic decomposition method has been studied with various sintering temperatures. The pure garnet phase was observed for the x = 1 powder at 900 °C sintering temperature, whereas the x = 0, 2 powder showed secondary phases. The x = 0 powder showed a similar crystallization process to that of the solid state reaction method. For the x =1, 2 powders, it is proposed that the lowering of the crystallization temperature is due to the lowered stability of the intermediate phase. The infrared spectroscopy and magnetic properties were also investigated. The pure garnet phase showed three absorption bands located at 563, 598, 655 cm−1 that shifted to 555, 588, 639 cm−1 along with an increase of bismuth concentration. The maximum values of saturation and remanence magnetization and the minimum value of coercivity were observed for the x = 1 powder sintered at 900 °C, which were 20.8 emu/g, 2.67 emu/g, and 31.9 Oe, respectively. 相似文献
14.
Ming He Shuren ZhangXiaohua Zhou Bo LiJing Wan 《Journal of Alloys and Compounds》2011,509(11):4260-4263
The behavior of dielectric and microwave properties against sintering temperature has been carried out on CaO-SiO2-B2O3 ceramic matrix composites with ZrO2 addition. The results indicated that ZrO2 addition was advantageous to improve the dielectric and microwave properties. X-ray diffraction (XRD) patterns show that the major crystalline β-CaSiO3 and a little SiO2 phase existed at the temperature ranging from 950 °C to 1050 °C. At 0.5 wt% ZrO2, CaO-SiO2-B2O3 ceramic matrix composites sintered at 1000 °C possess good dielectric properties: ?r = 5.85, tan δ = 1.59 × 10−4 (1 MHz) and excellent microwave properties: ?r = 5.52, Q · f = 28,487 GHz (11.11 GHz). The permittivity of Zr-doped CaO-SiO2-B2O3 ceramic matrix composites exhibited very little temperature dependence, which was less than ±2% over the temperature range of −50 to 150 °C. Moreover, the ZrO2-doped CaO-SiO2-B2O3 ceramic matrix composites have low permittivity below 5.5 over a wide frequency range from 20 Hz to 1 MHz. 相似文献
15.
The nickel-zinc ferrite (Ni0.8Zn0.2Fe2O4) thin films have been successfully deposited on stainless steel substrates using a chemical bath deposition method from alkaline bath. The films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), static water contact angle and cyclic voltammetry measurements. The X-ray diffraction pattern shows that deposited Ni0.8Zn0.2Fe2O4 thin films were oriented along (3 1 1) plane. The FTIR spectra showed strong absorption peaks around 600 cm−1 which are typical for cubic spinel crystal structure. SEM study revealed compact flakes like morphology having thickness ∼1.8 μm after air annealing. The annealed films were super hydrophilic in nature having a static water contact angle (θ) of 5°.The electrochemical supercapacitor study of Ni0.8Zn0.2Fe2O4 thin films has been carried out in 6 M KOH electrolyte.The values of interfacial and specific capacitances obtained were 0.0285 F cm−2 and 19 F g−1, respectively. 相似文献
16.
This study investigated the potential applications of microwave dielectric properties of Mg2SnO4 ceramics in mobile communication. Mg2SnO4 ceramics were prepared using a conventional solid-state method. The X-ray diffraction patterns of the Mg2SnO4 ceramics revealed no significant variation of phase with sintering temperature. A maximum density of 4.62 g/cm3, a dielectric constant (?r) of 8.41, a quality factor (Q × f) of 55,100 GHz, and a temperature coefficient of resonant frequency (τf) of −62 ppm/ °C were obtained when Mg2SnO4 ceramics were sintered at 1550 °C for 4 h. 相似文献
17.
Yih-Chien Chen Sheng-Kai YangKuang-Chiung Chang 《Journal of Alloys and Compounds》2011,509(39):9518-9522
The microwave dielectric properties of La(Mg0.5−xNixSn0.5)O3 ceramics were examined with a view to their exploitation for mobile communication. The La(Mg0.5−xNixSn0.5)O3 ceramics were prepared by the conventional solid-state method at various sintering temperatures. The X-ray diffraction patterns of the La(Mg0.4Ni0.1Sn0.5)O3 ceramics revealed no significant variation of phase with sintering temperatures. Apparent density of 6.71 g/cm3, dielectric constant (?r) of 20.19, quality factor (Q × f) of 74,600 GHz, and temperature coefficient of resonant frequency (τf) of −85 ppm/°C were obtained for La(Mg0.4Ni0.1Sn0.5)O3 ceramics that were sintered at 1550 °C for 4 h. 相似文献
18.
Liang FangDongjin Chu Huanfu Zhou Xiuli ChenHui zhang Baocheng ChangChunchun Li Yuandong QinXi Huang 《Journal of Alloys and Compounds》2011,509(35):8840-8844
The Li2ZnxCo1−xTi3O8 (x = 0.2-0.8) solid solution system has been synthesized by the conventional solid-state ceramic route and the effect of Zn substitution for Co on microwave dielectric properties of Li2CoTi3O8 ceramics has also been investigated. The microwave dielectric properties of these ceramics show a linear variation between the end members for all compositions. The optimized sintering temperatures of Li2ZnxCo1−xTi3O8 ceramics increase with increasing content of Zn. The specimen with x = 0.4 sintered at 1050 °C/2 h exhibits an excellent combination of microwave dielectric properties with ?r = 27.7, Qu × f = 57,100 GHz and τf = −1.0 ppm/°C. 相似文献
19.
Yue ShaoXiaolei Li Huiming JiXiaohong Sun Pei Cao 《Journal of Alloys and Compounds》2011,509(33):8345-8349
In this paper, the effect of α-Al2O3 on in situ synthesis low density O′-sialon multiphase ceramics was investigated. Thermodynamics analysis was used to illustrate the feasibility of synthesizing O′-sialon at a low temperature of 1420 °C. The crystalline phase and microstructure were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The actual substitution parameter x value of O′-sialon was estimated via lattice correction. The results showed that, O′-sialon multiphase ceramics with different x values could be synthesized successfully through varying α-Al2O3 content. Bulk densities of samples ranging from 1.64 to 2.11 g cm−3 were adjusted with the percentage of α-Al2O3 increasing from 5.21 wt.% to 15.62 wt.%. Formation of nearly single-phase O′-sialon was obtained in the sample containing 10.42 wt.% α-Al2O3. The actual substitution parameter x increased with the increase of α-Al2O3, whereas it was lower than the original designation, and the O′-sialon with a low x value was achieved. 相似文献
20.
This paper presents the sintering behaviour of a La0.9Sr0.1Ga0.8Mg0.2O2.85 coral-like microstructure powder. This is prepared by a successive freeze-drying and self-ignition process followed by calcination at 1200 °C during 1 h. This synthesis method gives great uniformity of the powder and allows shaping into compacts without requiring a grinding step. The grain size distribution (between 0.5 and 4 μm) favours a good sintering behaviour: open porosity disappear at 1400 °C and relative densities over 99% can be achieved after 6 h at 1450 °C. The same powder can also be sintered into a thin disc of ∼100 μm thickness. The characterization of the dense material by impedance spectroscopy shows that the activation energies below and above 600 °C are 1.0 eV and 0.7 eV, respectively. The conductivity at 800 °C is ∼0.11 S cm−1. Special attention is devoted to the temperature range between 200 °C and 400 °C, where the intragrain and intergrain contributions can be distinguished. The analysis of the parameters describing the intragrain constant phase element in the equivalent circuit suggests that, above 325 °C, the system evolves from a distribution of relaxation time to only one relaxation time. The analysis of the data by the complexes permittivity show that ionic oxide conduction mechanism would occur in two steps. In the first, an oxygen vacancy would be released and, in the second, the migration of the ionic oxide would take place in the material. 相似文献