共查询到20条相似文献,搜索用时 15 毫秒
1.
Microwave dielectric properties and microstructures of (Mg0.95Co0.05)TiO3 ceramics prepared by a new sintering method (reaction-sintering method) were investigated. A pure phase of (Mg0.95Co0.05)TiO3 was obtained by the new method and excellent dielectric properties were observed due to uniformities of the microstructure and the phase. In contrast, the secondary phase (Mg0.95Co0.05)Ti2O5 was observed in samples prepared by conventional sintering method. In order to study the influence of secondary phase on the microwave dielectric properties quantitatively, the weight fraction of (Mg0.95Co0.05)Ti2O5 was calculated on the basis of Rietveld refinement. The pore-free?r values of specimens prepared by two different methods indicated that porosity plays an important role in the ?r values of (Mg0.95Co0.05)TiO3 ceramics. Specimens sintered by reaction-sintering method at 1350 °C for 4 h possess excellent dielectric properties with an ?r of 16.3, a Q × f value of 244,500 GHz, and a τf value of −53.5 ppm/°C. 相似文献
2.
The microwave dielectric properties and the microstructures of ZnO-doped La(Co1/2Ti1/2)O3 ceramics prepared by conventional solid-state route have been studied. Doped with ZnO (up to 0.75 wt%) can effectively promote the densification of La(Co1/2Ti1/2)O3 ceramics with low sintering temperature. At 1320 °C, La(Co1/2Ti1/2)O3 ceramics with 0.75 wt% ZnO addition possesses a dielectric constant (r) of 30.2, a Q × f value of 73,000 GHz (at 8 GHz) and a temperature coefficient of resonant frequency (τf) of −35 ppm/°C. 相似文献
3.
Production of nanoscale Ba(Zn1/3Nb2/3)O3 microwave dielectric ceramics by polymerised complex method
Ba(Zn1/3Nb2/3)O3 nanoparticles have been synthesized by a polymerised complex method by using precursor materials of barium nitrate, zinc acetate, niobium oxide, hydrofluoric acid and citric acid. Thermal decomposition characteristics and crystallization behavior of the powders were investigated by the thermogravimetric and differential thermal analysis, X-ray diffractometer and Fourier transform infrared spectroscopy. Ba(Zn1/3Nb2/3)O3 phase started to form at low temperature of 400 °C and, single phase Ba(Zn1/3Nb2/3)O3 perovskite structure was obtained at 1000 °C. Microstructural investigation revealed that the major particle size of Ba(Zn1/3Nb2/3)O3 nanoparticles were in the range of 80–110 nm with spherical morphology and homogeneous size distribution. But the powders also contained some agglomeration. 相似文献
4.
Sinterability and dielectric properties of Ba0.55Sr0.4Ca0.05TiO3-CaTiSiO5-Mg2TiO4 composite ceramics
Qianqian JiaHuiming Ji Xiaolei LiShan Liu Zhengguo Jin 《Journal of Alloys and Compounds》2011,509(41):10155-10160
The composite ceramics of Ba0.55Sr0.4Ca0.05TiO3-CaTiSiO5-Mg2TiO4 (BSCT-CTS-MT) were prepared by the conventional solid-state route. The sintering performance, phase structures, morphologies, and dielectric properties of the composite ceramics were investigated. The BSCT-CTS-MT ceramics were sintered at 1100 °C and possessed dense microstructure. The dielectric constant was tailored from 1196 to 141 as the amount of Mg2TiO4 increased from 0 to 50 wt%. The dielectric constant and dielectric loss of 40 wt% Ba0.55Sr0.4Ca0.05TiO3-10 wt% CaTiSiO5-50 wt% Mg2TiO4 was 141 and 0.0020, respectively, and the tunability was 8.64% under a DC electric field of 8.0 kV/cm. The Curie peaks were broadened and depressed after the addition of CaTiSiO5. The optimistic dielectric properties made it a promising candidate for the application of tunable capacitors and phase shifters. 相似文献
5.
Phase evolution and microwave dielectric properties of (1 − x)(Mg0.95Co0.05)2TiO4-xTiO2 (x = 0-1) ceramics prepared by the conventional mixed oxide route have been investigated. Increasing the TiO2 content would lead to a main phase transformation from (Mg0.95Co0.05)2TiO4 to (Mg0.95Co0.05)TiO3, (Mg0.95Co0.05)Ti2O5 and then TiO2. Not only did the TiO2 addition compensate the τf, it also lowered the sintering temperature of specimen. A huge drop of Q × f occurs at a 40-60 mol% TiO2 addition was attributed to the formation of (Mg0.95Co0.05)Ti2O5 phase. Specimen with x = 0.78 can possess an excellent combination of microwave dielectric properties: ?r ∼ 24.77, Q × f ∼ 38,500 GHz and τf ∼ −1.3 ppm/°C. 相似文献
6.
Zhenhua Xu Shimei HeLimin He Rende MuGuanghong Huang Xueqiang Cao 《Journal of Alloys and Compounds》2011,509(11):4273-4283
Double-ceramic-layer (DCL) thermal barrier coatings (TBCs) of La2(Zr0.7Ce0.3)2O7 (LZ7C3) and yttria stabilized zirconia (YSZ) were deposited by electron beam-physical vapor deposition (EB-PVD). The thermal cycling test at 1373 K in an air furnace indicates the DCL coating has a much longer lifetime than the single layer LZ7C3 coating, and even longer than that of the single layer YSZ coating. The superior sintering-resistance of LZ7C3 coating, the similar thermal expansion behaviors of YSZ interlayer with LZ7C3 coating and thermally grown oxide (TGO) layer, and the unique growth modes of columns within DCL coating are all very helpful to the prolongation of thermal cycling life of DCL coating. The failure of DCL coating is mainly a result of the reduction-oxidation of cerium oxide, the crack initiation, propagation and extension, the abnormal oxidation of bond coat, the degradation of t′-phase in YSZ coating and the outward diffusion of Cr alloying element into LZ7C3 coating. 相似文献
7.
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
8.
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
9.
Jeong-Hun JuKwang-Sun Ryu 《Journal of Alloys and Compounds》2011,509(30):7985-7992
The core-shell structure cathode material Li(Ni0.8Co0.15Al0.05)0.8(Ni0.5Mn0.5)0.2O2 (LNCANMO) was synthesized via a co-precipitation method. Its applicability as a cathode material for lithium ion batteries was investigated. The core-shell particle consists of LiNi0.8Co0.15Al0.05O2 (LNCAO) as the core and a LiNi0.5Mn0.5O2 as the shell. The thickness of the LiNi0.5Mn0.5O2 layer is approximately 1.25 μm, as estimated by field emission scanning electron microscopy (FE-SEM). The cycling behavior between 2.8 and 4.3 V at a current rate of 18 mA g−1 shows a reversible capacity of about 195 mAh g−1 with little capacity loss after 50 cycles. High-rate capability testing shows that even at a rate of 5 C, a stable capacity of approximately 127 mAh g−1 is retained. In contrast, the capacity of LNCAO rapidly decreases in cyclic and high rate tests. The observed higher current rate capability and cycle stability of LNCANMO can be attributed to the lower impedance including charge transfer resistance and surface film resistance. Differential scanning calorimetry (DSC) indicates that LNCANMO had a much improved oxygen evolution onset temperature of approximately 251 °C, and a much lower level of exothermic-heat release compared to LNCAO. The improved thermal stability of the LNCANMO can be ascribed to the thermally stable outer shell of LiNi0.5Mn0.5O2, which suppresses oxygen release from the host lattice and not directly come into contact with the electrolyte solution. In particular, LNCANMO is shown to exhibit improved electrochemical performance and is a safe material for use as an electrode for lithium ion batteries. 相似文献
10.
用高能集中的二氧化碳激光束作为诱导热源,在普通低碳钢Q235基材上熔覆了含有碳氮化钛增强粒子的铁基熔覆层,用光镜、扫描电镜、X射线衍射、电子探针等手段对复合熔覆层中的粒子成分、形貌、大小进行了分析,并采用光学显微硬度计对复合熔覆层的显微硬度进行了测试.结果表明,加入的颗粒状TiN与石墨粉在激光熔覆过程中发生了反应,原位生成了新的颗粒状强化相Ti(C0.3N0.7).在熔覆层中Ti(C0.3N0.7)的形貌特征多呈尺寸不等近似菱形颗粒及其它不规则形状,大小在0.1~5μm之间,弥散分布.新Ti(C0.3N0.7)颗粒相的生成使得熔覆层得到了强化,熔覆层的显微硬度达到600~700HV0.2. 相似文献
11.
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
12.
Zhihang Peng Qiang ChenJiagang Wu Xiaohong ZhuDingquan Xiao Jianguo Zhu 《Journal of Alloys and Compounds》2011,509(33):8483-8486
Sb5+-doped (NaBi)0.38(LiCe)0.05[]0.14Bi2Nb2O9 (represented as NBNLCS-x, where [] represents A-site vacancies) ceramics were prepared by the conventional solid-state route. The ceramics well sintered to approach ∼98.5% theoretical density and the tetragonality of crystal structure increased with Sb5+ additions. However, the Curie temperature (TC) and the piezoelectric coefficient (d33) of Sb5+-modified ceramics gradually decreased. The 3 mol% Sb5+-doped samples exhibited optimum properties with a d33 value of ∼22 pC/N planar electromechanical coupling factor (kp) of ∼11.2% and relatively high TC of ∼765 °C. These results indicate that NBNLCS-x material is a promising candidate for high-temperature piezoelectric applications. 相似文献
13.
首先以AlO2-为铝源,采用三元共沉淀法制备前驱体Ni_(0.8)Co_(0.15)Al_(0.05)(OH)_2。对前驱体进行500℃高温处理,随后与过量的锂盐混合均匀,在氧气气氛下700℃煅烧12 h制得LiNi_(0.8)Co_(0.15)Al_(0.05)O_2(NCA)材料。采用X射线衍射仪(XRD)测试可知,所得的NCA材料呈典型的α-NaFeO_2层状结构,属于R-3m空间群。扫描电子显微镜(SEM)测试显示,NCA为粒径5~6μm的球状颗粒。材料在电流倍率为0.1C下首次放电容量为167.1mAh/g,循环200次以后容量保持率为96.2%。倍率测试表明,0.1、10 C下NCA的容量分别为184.0、112.7 mAh/g,到恢复到0.1 C时,容量仍可达179.7mAh/g,具有比较好的倍率性能。 相似文献
14.
Piezoelectric and dielectric properties of Dy2O3-doped (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics
Chen Zhi-hui Ding Jian-ning Mei LinYuan Ning-yi Zhu Yuan-yuan 《Journal of Alloys and Compounds》2011,509(2):482-485
(Bi0.5Na0.5)0.94Ba0.06TiO3 + x wt% Dy2O3 with x = 0-0.3 ceramics were synthesized by conventional solid-state processes. The effects of Dy2O3 on the microstructure, the piezoelectric and dielectric properties were investigated. X-ray diffraction pattern confirmed that the coexistence of tetragonal and rhombohedral phases in the (Bi0.5Na0.5)0.94Ba0.06TiO3 composition was not changed by adding 0.05-0.3 wt% Dy2O3. SEM images indicate that all the ceramics have pore-free microstructures with high density, and that doping of Dy2O3 inhibits the grain growth of the ceramics. The addition of Dy2O3 shows the double effects on decreasing the piezoelectric and dielectric properties for 0 < x < 0.15 when Dy3+ ions substitute B-site Ti4+ ions, and increasing the properties for 0.15 < x < 0.3 when Dy3+ ions enters into A-site of the perovskite structure. The optimum electric properties of piezoelectric constant d33 = 170 pC/N and the dielectric constant ?r = 1900 (at a frequency of 1 kHz) are obtained at x = 0.3. 相似文献
15.
采用铸造方法制备具有不同SiCp含量(0.5%~2.0%,质量分数,下同)的SiCp/Mg94Zn5Y1复合材料,并研究了复合材料的力学性能和阻尼性能。通过扫描电子显微镜和X射线衍射仪测试复合材料的微观组织结构和物相组成。在基体中加入SiCp之后,SiCp均匀分布在基体中,增强体细化了复合材料的微观组织结构。SiCp/Mg94Zn5Y1复合材料包括α-Mg、I相(准晶相)和SiCp相。分别使用动态热机械分析仪和AG-X试验机测试了SiCp/Mg94Zn5Y1复合材料的阻尼性能和力学性能。复合材料的力学性能优于Mg94Zn5Y1合金,1.0%SiCp/Mg94Zn5Y1复合材料的抗压缩强度高达350 MPa;所有复合材料的阻尼性能都远高于基体合金的阻尼性能,其中0.5%SiCp/Mg94Zn5Y1复合材料具有最佳的阻尼性能。此外,根据功效系数法,SiCp含量为1.0%的SiCp/Mg94Zn5Y1复合材料具有良好的综合性能。 相似文献
16.
D.H. Manh P.T. PhongT.D. Thanh D.N.H. NamL.V. Hong N.X. Phuc 《Journal of Alloys and Compounds》2011,509(5):1373-1377
La0.7Ca0.3MnO3 (LCMO) nanoparticles with average diameter of 16-73 nm were prepared by reactive milling and thermal processing methods. Interaction and size effects on the magnetic properties of the LCMO nanoparticle samples were investigated. Phenomena related to the interparticle interaction, such as an un-overlapping of the M(Hext,T)/MS vs. Hext/T scaling plots and a Curie-Weiss rather than Curie law behavior of the dc susceptibility at high temperatures were analyzed. The magnetization curves of interacting nanoparticles were well described by using the mean-field approximation. The dependence of the blocking temperature TB on the strength of the interactions, magnetic anisotropy, as well as the thermal dependence of magnetization deviates from the expected Bloch law was also estimated. 相似文献
17.
Ching-Fang Tseng 《Journal of Alloys and Compounds》2011,509(39):9447-9450
The influence of Zr substitution for Ti on the microwave dielectric properties and microstructures of the Mg(ZrxTi1−x)O3(MZxT) (0.01 ≤ x ≤ 0.3) ceramics was investigated. The quality factors of Mg(ZrxTi1−x)O3 ceramics with x = 0.01-0.05 were improved because the solid solution of a small amount of Zr4+ substitution in the B-site could increase density and grain size. An excess of Zr4+ resulted in the formation of a great deal of secondary phase that declined the microwave dielectric properties of MZxT ceramics. The temperature coefficient of resonant frequency (τf) of Mg(ZrxTi1−x)O3 ceramics slightly increased with increasing Zr content, and the variation in τf was attributed to the formation of secondary phases. 相似文献
18.
采用氢氧化物共沉淀法合成前驱体Ni0.5Cc0.2Mn0.3H(OH)2,进一步用高温固相法与锂源共混煅烧得到LiNi0.5Co0.2Mn0.3O2。初步探讨了前驱体与锂源在高温煅烧过程中的质量变化及煅烧工艺对材料结构和性能的影响。热重分析(TGA)表明在煅烧过程中750℃后材料质量几乎没有变化。X射线衍射(XRD)对750℃-900℃的材料进行结构分析,结果表明所有材料具有良好的α-NaFeO2层状结构和较小的阳离子混排度。扫描电镜(SEM)分析表明材料具有表面光滑,分布均匀的球形结构。横流充放电测试结果表明在850℃煅烧的材料具有最好的电学性能,在0.2C,2.5-4.6V测试条件下,其具有193.7mAh/g的首次放电容量,循环30次后的容量保持率为94.2%,并且具有最好的倍率性能。 相似文献
19.
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
20.
The microwave dielectric properties and the microstructures of the (1 − x)(Mg0.6Zn0.4)0.95Co0.05TiO3–xCa0.61Nd0.26TiO3 ceramic system were investigated. In order to achieve a temperature-stable material, we studied a method of combining a positive temperature coefficient material with a negative one. Ca0.61Nd0.26TiO3 has a large positive temperature coefficient of resonant frequency. (Mg0.6Zn0.4)0.95Co0.05TiO3 possesses a negative temperature coefficient of resonant frequency. By appropriately adjusting the x value in the (1 − x)(Mg0.6Zn0.4)0.95Co0.05TiO3–xCa0.61Nd0.26TiO3 ceramic system, a near-zero τf value can be obtained. A new microwave dielectric material of 0.8(Mg0.6Zn0.4)0.95Co0.05TiO3–0.2Ca0.61Nd0.26TiO3 possesses the excellent dielectric properties of a dielectric constant of 28.6, a Q × f value of 80,600 GHz and a temperature coefficient of resonant frequency of 4.1 ppm/°C and has a lower sintering temperature of 1250 °C. 相似文献