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1.
In this study, we will develop the influences of the excess x wt% ( x=0, 1, 2, and 3) Bi 2O 3-doped and the different fabricating process on the sintering and dielectric characteristics of 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3 ferroelectric ceramics with the aid of SEM and X-ray diffraction patterns, and dielectric–temperature curves. The 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3+ x wt% Bi 2O 3 ceramics are fabricated by two different processes. The first process is that (Na 0.5Bi 0.5)TiO 3 composition is calcined at 850 °C and BaTiO 3 composition is calcined at 1100 °C, then the calcined (Na 0.5Bi 0.5)TiO 3 and BaTiO 3 powders are mixed in according to 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3+ x wt% Bi 2O 3 compositions. The second process is that the raw materials are mixed in accordance to the 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3+ x wt% Bi 2O 3 compositions and then calcining at 900 °C. The sintering process is carried out in air for 2 h from 1120 to 1240 °C. After sintering, the effects of process parameters on the dielectric characteristics will be developed by the dielectric–temperature curves. Dielectric–temperature properties are also investigated at the temperatures of 30–350 °C and at the frequencies of 10 kHz–1 MHz. 相似文献
2.
Magnetoelectric composites, namely, xNiFe 2O 4+(1− x)Ba 0.9Sr 0.1TiO 3 were prepared by standard double sintering ceramic method. The X-ray diffraction analysis was carried out to check the phases formed during sintering and to calculate the lattice parameters. Scanning electron microscope (SEM) micrographs were taken to understand the microstructure of the samples. The dielectric constant ( ε′) and loss tangent (tan δ) were measured as a function of frequency in the frequency range 100 Hz–1 MHz. Variation of dielectric constant and loss tangent with temperature and composition has been reported. The hysteresis measurements were done to determine saturation magnetization ( MS) and coersivity ( Hc). The variation of saturation magnetization and magnetic moment is interpreted in terms of composition. 相似文献
3.
The nonlinear optical properties of a phosphate vitreous system [(ZnO) x-(MgO) 30-x-(P 2 O 5) 70], where x=8, 10, 15, 18, and 20 mol% synthesized through the melt-quenching technique have been investigated by using the Z-scan technique. In the experiment, a continuous-wave laser with a wavelength of 405 nm was utilized to determine the sign and value of the nonlinear refractive (NLR) index and the absorption coefficient with closed and opened apertures of the Z-scan setup. The NLR index was found to increase with the ZnO concentration in the glass samples by an order of 10 -10 cm 2·W -1. The real and imaginary parts of the third-order nonlinear susceptibility were calculated by referring to the NLR index (n 2) and absorption coefficient (β) of the samples. The value of the third-order nonlinear susceptibility was presented by nonlinear refractive or absorptive behavior of phosphate glasses for proper utilization in nonlinear optical devices. Based on the measurement, the positive sign of the NLR index shows a self-focusing phenomenon. The figures of merit for each sample were calculated to judge the potential of phosphate glasses for application in optical switching. 相似文献
4.
以Li 2CO 3、Nb 2O 5、TiO 2和Eu 2O 3为原料,采用固相法制备Eu 3+掺杂的5Li 2CO 3-1Nb 2O 5-5TiO 2(LNT)发光介质陶瓷。通过密度、XRD和荧光光谱测试,对0.2%(质量分数)Eu 2O 3掺杂的陶瓷片进行性能表征。结果表明:1 120℃烧结致密的陶瓷片,其晶相结构为“M-相”与Li 2TiO 3两相复合构成;在400 nm的近紫外光激发下,样品有较强的橙光(592 nm)和红光(615 nm)发射,分别属于Eu 3+的 5D 0→ 7F 1的磁偶极跃迁和 5D 0→ 7F 2的电偶极跃迁。 相似文献
5.
CaCu 3Ti 4O 12介电损耗较大且损耗机理尚不明确, 因此限制了其应用.本文采用固相法和共沉淀法合成CaCu 3Ti 4O 12陶瓷, 利用宽带介电温谱研究在交流小信号作用下, 双Schottky势垒耗尽层边缘深陷阱的电子松弛过程、 载流子松弛过程以及CaCu 3Ti 4O 12陶瓷的介电损耗性能. 研究发现, 在低频下以跳跃电导和直流电导的响应为主, 而高频下主要为深陷阱能级的松弛过程所致, 特别是活化能为0.12 eV的深陷阱浓度, 这是决定CaCu 3Ti 4O 12陶瓷高频区介电损耗的重要因素.降低直流电导, 有利于降低低频区介电损耗; 而高频区介电损耗的降低, 需要降低深陷阱浓度或增大晶粒尺寸. 共沉淀法制备的CaCu 3Ti 4O 12陶瓷, 有效降低直流电导及控制深陷阱浓度, 介电损耗降低明显.
关键词:
3Ti 4O 12陶瓷')" href="#">CaCu 3Ti 4O 12陶瓷
介电损耗
松弛过程
Schottky势垒 相似文献
6.
0.9Pb(Zn 1/3Nb 2/3)–0.1BaTiO 3 (0.9PZN–0.1BT) of perovskite structure has been successfully prepared by mechanically activating mixed oxides of PbO, ZnO, Nb 2O 5, BaO and TiO 2. The novel mechanochemical technique skips the phase-forming calcination step at an intermediate temperature that is always required in both the conventional solid state reaction and chemistry-based precursor routes. Ultrafine 0.9PZN–0.1BT particles of perovskite structure were formed when the constituent oxides were mechanically activated for more than 10 h. The powder was sintered to a density of 96% theoretical density at 1100°C for 1 h. The sintered 0.9PZN–0.1BT exhibits perovskite structure and a peak dielectric constant of 8800 at the Curie temperature of 60°C when measured at a frequency of 100 Hz. 相似文献
7.
The effects of the addition of H 3 BO 3 on the microstructure, phase formation, and microwave dielectric properties of (Zn 0.7 Mg 0.3 )TiO 3 ceramics sintered at temperatures ranging from 890 ℃ to 950 ℃ are investigated. H 3 BO 3 as a sintering agent can effectively lower the sintering temperature of ZMT ceramics below 950 ℃ due to the liquid-phase effect. The microwave dielectric properties are found to strongly correlate with the amount of H 3 BO 3 . With the increase in H 3 BO 3 content, the dielectric constant (ε r ) monotonically increases, but the quality factor (Q × f ) reaches a maximum at 1 wt% H 3 BO 3 , and the apparent density of ZMT ceramics with H 3 BO 3 ≥ 1 wt% gradually decreases. At 950 ℃, the ZMT ceramics with 1% H 3 BO 3 exhibit excellent microwave dielectric properties: ε r = 19.8, and Q × f = 43800 GHz (8.94 GHz). 相似文献
8.
In this paper, the preparation of 0.08BiGaO_3–0.90BaTiO_3–0.02LiNbO_3 is investigated at pressure 3.8 GPa and temperature 1100–1200?C. Experimental results indicate that not only is the sintered rate more effective, but also the sintered temperature is lower under high pressure and high temperature than those of under normal pressure. It is thought that the adscititious pressure plays the key role in this process, which is discussed in detail. The composition and the structure of the as-prepared samples are recorded by XRD patterns. The result shows that the phases of Ba TiO_3, BaBiO_(2.77), and Ba_2Bi_4Ti_5O_(18) with piezoelectric ceramic performance generate in the sintered samples. Furthermore, the surface morphology characteristics of the typical samples are also investigated using a scanning electron microscope. It indicates that the grain size and surface structure of the samples are closely related to the sintering temperature and sintering time. It is hoped that this study can provide a new train of thought for the preparation of lead-free piezoelectric ceramics with excellent performance. 相似文献
9.
With the interest in using lead-free materials to replace lead-containing materials increasing,the use of Na_(0.5)Bi_(0.5)TiO_3(NBT) has come into our sight.We studied the composition of NBT and found that NaBiTi_6O_(14) ceramics can be compositionally tuned by Mg-doping on the Ti-site to optimize the dielectric properties.In this study,Mg-doped NaBiTi_6O_(14)(NaBi(Ti_(0.98)Mg_(0.02))_60_(14-d)) ceramics were prepared by a conventional mixed oxide route at different sintering temperatures,and their dielectric properties have been studied at a wide temperature range.X-ray diffraction(XRD) patterns of the NBT-based ceramics indicate that all samples have a pure phase without any secondary impurity phase.The experimental data show that after Mg-doping,the relative permittivity and dielectric loss become lower at 1040,1060,and1080 ℃ except 1020 ℃ and at different frequencies from 10 kHz,100 kHz to 1 MHz.Take 1060 ℃ for example,when the sintering temperature is 1060 ℃ at 1 MHz,the minimum relative permittivity of NaBiTi_6O_(14) is 32.9 and the minimum dielectric loss is 0.01417,the relative permittivity of NaBi(Ti_(0.98)Mg_(0.02))_60_(14-δ) under the same condition is 25.8 and the dielectric loss is 0.000104.We explored the mechanism of Mg-doping and surprisingly found that the dielectric property of NaBi(Ti_(0.98)Mg_(0.02))_60_(14-δ) becomes better owing to Mg-doping.Thus,NaBi(Ti_(0.98)Mg_(0.02))_60_(14-δ) can be used in microwave ceramics and applied to new energy materials. 相似文献
10.
S-doped TiO 2 (S-TiO 2) photocatalyst was synthesized by sol–gel method with tetrabutyl titanate and thiourea as precursor. S-TiO 2 was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis absorption spectroscopy, transmission electron microscopy (TEM) and the photocatalytic activity was evaluated by 1-naphthol-5-sulfonic acid (L-acid) under UV, visible light and solar light radiation. The results showed that doped S could improve photoabsorption property of TiO 2 in the visible region, leading the increase in the photocatalytical activity of TiO 2. The average particle size of the S-TiO2 photocatalyst is about 10 nm. The S-TiO2-4 photocatalyst contains 100% anatase crystalline phase of TiO2. In the S-TiO2-4 photocatalyst, S does not exist independently, but is incorporated into the crystal lattice of TiO2. In the inner crystal lattice of the S-TiO2-4 photocatalyst, S as S2− replaces O in TiO2, while on the surface of crystal lattice, S exists as S4+ and S6+. The photocatalytical activity of S-TiO2-4 photocatalyst for the photodegradation of L-acid is better than that of pure TiO2. Under the same conditions, the photodegradation efficiency of L-acid for the S-TiO2-4 photocatalyst and the solar light irradiation is 85.1%, while it is only 26.4% for pure TiO2. In addition, the final products of the photocatalysis of L-acid using the S-TiO2-4 photocatalyst are not organic compounds with low molecular weight, but the inorganic compounds. 相似文献
11.
两种非晶锂离子导体B 2O 3-0.7Li 2O-0.7LiCl-xAl 2O 3-0.1V 2O 5(x=0.05和0.15)的电子自旋共振谱研究表明:(i)ESR线型是高斯型,证实V 2O 5添加量适当;(ii)超精细结构来源于VO 2+络离子,具有四角对称性,属C 4v群。越精细耦合张量的平行分量平均值 A//=0.0175cm -1,垂直分量 A⊥=0.0063cm -1。由 g//( g⊥)求出其基态 2B 2g与第一激发态 2E g的能级间距△ 1=2.46×10 4 cm -1,基态与第二激发态 2B 1g的能级间距△ 2=3.03×10 4 cm -1;(iii)变温实验证实:Al 2O 3组分较少(x=0.05)的非晶ESR强度比x=0.15的非晶高3倍至2倍,而Al 2O 3组分越多则ESR强度随温升下降越小。 相似文献
12.
采用匀胶法制备了厚度在微米量级的 Si/[TiO 2/Al 2O 3] 2TiO 2和Si/[TiO 2/MgO] 2/TiO 2 多层介质膜反射镜. 采用太赫兹(THz)时域透射光谱系统获得了多层膜的时域透射谱. 用传输矩阵法模拟了Si/[TiO 2/Al 2O 3] 2TiO 2 和Si/[TiO 2/MgO] 2/TiO 2两种分布式布拉格反射镜 (DBR)的反射相移和相位穿透深度等光学特性. 设计了两种结构为 DBR/LT-GaAs/DBR的对称THz光学微腔结构并模拟了腔结构的辐射光谱. 结果表明:通过引入谐振腔, 两种DBR组成的微腔器件在谐振波长处的强度分别提高了19和14倍. 其中Si/[TiO 2/Al 2O 3] 2TiO 2/LT-GaAs (12 μm)/ [TiO 2/Al 2O 3] 2TiO 2腔的辐射光谱存在两个峰, 分别位于208和248 μm, 并分析了出现两个谐振峰的原因. 探讨了通过引入介质谐振腔实现对THz源的辐射特性进行调控的可行性.
关键词:
分布式布拉格反射镜
光子晶体
穿透深度
太赫兹微腔 相似文献
13.
按照50Nb 2O 5-(46-x)Y 2O 3-4Yb 2O 3-xTm 2O 3(x=0.1,0.2,0.5,1,2)的配比方式,采用高温固相法制备出了掺杂Tm 3+/Yb 3+的YNbO 4晶体粉末。在980 nm红外光激发下,观测到波长为478,645,707 nm的上转换荧光,分别对应于Tm 3+离子的 1G 4→ 3H 6、 1G 4→ 3F 4、 3F 3→ 3H 6能级跃迁过程。利用上转换发射功率与980 nm激光器工作电流关系估算出跃迁过程吸收光子数目为2.72,2.69,2.01,从而确定出前两者为三光子吸收过程,最后一个对应于双光子吸收过程。运用Judd-Ofelt理论研究样品光谱特性,根据样品的吸收谱得到样品的谱线强度参数Ω t(t=2,4,6),进而得出理论振子强度及实验振子强度,二者均方根偏差δ rms=1.299×10 -7。计算了Tm 3+离子向下能级跃迁的跃迁几率、跃迁分支比等参数。最后得出结论:(1) 3F 4能级寿命较长,适合作为上转换中间能级;(2) 3H 5能级寿命较长,且 3H 5→ 3H 6跃迁分支比(96.46%)接近100%,可用于产生1 216 nm激光。 相似文献
14.
为了寻求新的非常规多铁性材料,采用固相合成方法制备具有Ruddlesden-Popper结构的(1-x)Sr_3Sn_2O_7+x Ca_3Mn_2O_7(SSO+CMO)(x=0,0.05,0.10,0.15,0.20)系列陶瓷.通过X射线衍射、紫外可见光谱和磁性测量,发现SSO+CMO陶瓷为单一正交相结构,空间群为A21am.随着掺杂量x的增加,样品的晶胞参数和体积相应地减小;在室温不同频率下,样品的介电常数和介电损耗随着频率增加而减小,且在x=0.1时有弱的铁磁性. 相似文献
15.
为了制备ZnO释能电阻并研究Al掺杂浓度对ZnO释能电阻材料的影响,通过改进的制陶工艺制备了不同Al掺杂浓度的ZnO导电陶瓷。实验结果表明,Al掺杂浓度对ZnO释能电阻的导电性、能量密度和线性度均有较大的影响。Al的掺杂能较好地改善ZnO释能电阻的线性度,非线性系数可低至1.02;Al掺杂能很好地控制ZnO的电阻率,使其达到0.54 Ω·cm;Al掺杂还能较好地改善ZnO陶瓷的均匀性和密度,从而提高ZnO释能电阻的能量吸收密度,能量吸收密度高达720 J/cm 3,较金属释能材料高出2~3倍。 相似文献
16.
采用基于密度泛函理论的平面波超软赝势法研究了Magneli相亚氧化钛Ti8O15的电子结构和光学性能.计算出的能带结构显示Ti 8O 15相比锐钛型TiO 2禁带宽度大幅度降低.态密度分析表明,其原因在于Ti 8O 15的O原子的2p轨道以及Ti原子的3p,3d轨道相对于TiO 2的相应轨道向左产生了偏移,同时由于O原子的缺失使得Ti原子的3d,3p轨道多余电子在Fermi能级附近聚集形成新的电子能级.态密度分析结果还显示,相对于TiO 2,Ti 8O 15Fermi能级附近电子格局发生了如下变化:O原子的2p轨道电子贡献减少,Ti原子的3d轨道的电子对Fermi能级贡献增大.光吸收计算图谱表明,TiO 2仅在紫外光区有较高的光吸收能力,而Ti 8O 15由于禁带宽度变窄引起光吸收范围红移到可见光区,从而在紫外光区和可见光区都有较高的光吸收能力,计算结果与实验得到的紫外-可见漫反射吸收光谱结果一致. 相似文献
17.
采用固相烧结法制备了Zri_(1-x)Al_(2-x)V_(2-x)Mo_xO_7(0≤x≤0.9),并通过调整Al~(3+)/Mo~(6+)对ZrV_2O_7中的Zr~(4+)/V~(5+)离子替代量来实现近零膨胀,对于较小的x值(x≤0.3),材料保持了与ZrV_2O_7相同的立方相结构.随着Al~(3+)/Mo~(6+)替代量的增加,(Al/Zr)~-和(Mo/V)~+之间的库仑相互作用逐渐加强,这种库仑相互作用导致材料中未发生畸变的立方相晶体结构逐渐减少.当x≥0.7时,材料中立方相晶体结构完全消失.在425-750 K温度区间内,Zr_(0.5)Al_(0.5)M_(0.6)O_7展示出近零膨胀性质(-0.39×l0~(-6)K~(-1)).Zr_(0.5)Al_(1.5)V_(1.5)Mo_(0.5)O_7的低热膨胀性能可能与Al~(3+)/Mo~(6+)对ZrV_2O_7中Zr~(4+)/V~(5+)部分替代引起部分晶体结构发生的畸变及其对未替代部分的晶格结构的影响有关. 相似文献
18.
磁通钉扎性能对GdBa 2Cu 3O 7-δ超导块材的实际应用具有重要的影响, 而引入合适的第二相粒子可以改善GdBa 2Cu 3O 7-δ 超导块材的磁通钉扎性能.本文采用顶部籽晶熔融织构法成功地制备出纳米微粒BaFe 12O 19(<100 nm)掺杂的超导块材, 样品的最终组分为Gd123+ 0.4 Gd211+ x BaFe 12O 19 (x=0, 0.2 mol%, 0.4 mol%, 0.8 mol%)+ 10 wt%Ag 2O+ 0.5 wt%Pt. 通过研究不同掺杂量的BaFe 12O 19微粒对GdBa 2Cu 3O 7-δ 超导块材微观结构和超导性能的影响, 结果表明当掺杂量为0.2 mol%时, 样品的临界电流密度几乎在整个外加磁场下都有明显的提高.在零场下, 临界电流密度达到5.5× 10 4 A/cm 2. 纳米微粒BaFe 12O 19不仅可以保持掺杂前的化学组成, 作为有效的钉扎中心存在于超导块材中, 并且能够改善Gd 2BaCuO 5粒子的分布和细化Gd 2BaCuO 5粒子, 使Gd 2BaCuO 5粒子的平均粒径由未掺杂时的1.4 μ m减小到掺杂后的0.79 μ m, 进而提高了超导块材的临界电流密度和俘获磁场, 明显提高了GdBa 2Cu 3O 7-δ 超导块材的超导性能.临界温度 TC也有所提升, 并能够维持在92.5 K左右. 该结果为进一步研究纳米磁通钉扎中心的引入并改善GdBa 2Cu 3O 7-δ 超导块材的性能有着重要的意义. 相似文献
19.
在实验上, W掺杂量在0.02083–0.04167的范围内时, 有关掺杂体系的电导率影响的研究有两种相悖的结论. 为解决这个问题, 本文采用第一性原理平面波模守恒赝势方法, 首先构建了两种Ti 0.97917W 0.02083O 2 和Ti 0.95833W 0.04167O 2 超胞模型, 分别对这两种模型进行了几何结构优化、能带结构分布和态密度分布计算. 同时还计算了掺杂体系的电子浓度、有效质量、迁移率和电导率. 计算结果表明, 在电子自旋极化或电子非自旋极化的条件下, W掺杂浓度越大、掺杂体系的电子浓度越大、有效质量越小、迁移率越小、电导率越大、导电性能越强. 由电离能和Bohr半径分析进一步证实了Ti 0.95833W 0.04167O 2 超胞的导电性能优于Ti 0.97917W 0.02083O 2 超胞. 为了研究掺杂体系的结构稳定性和形成能, 又分别构建了Ti 0.96875W 0.03125O 2, Ti 0.9375W 0.0625O 2两种超胞模型, 几何结构优化后进行了计算, 结果表明, 在电子自旋极化或电子非自旋极化的条件下, 在W掺杂量为0.02083–0.04167的范围内, W掺杂浓度越大、掺杂体系的总能量越高、稳定性越差、 形成能越大、掺杂越困难. 将掺杂体系的晶格常数与纯的锐钛矿TiO 2相比较, 发现沿a轴方向的晶格常数变大、沿c轴方向的晶格常数变小、掺杂体系的体积变大, 计算结果与实验结果相符合. 在电子自旋极化的条件下, 掺杂体系形成了半金属化的室温铁磁性稀磁半导体. 相似文献
20.
利用传统的固相反应法制备了BiFe 1-xMn xO 3 ( x= 0-0.20)陶瓷样品, 研究了不同Mn 4+掺杂量对BiFeO 3陶瓷密度、物相结构、显微形貌、 介电性能和铁电性能的影响.实验结果表明:所制备的BiFe 1-xMn xO 3 陶瓷样品的钙钛矿主相均已形成,具有良好的晶体结构, 且在掺杂量x=0.05附近开始出现结构相变.随着Mn 4+添加量的增加, 体系的相结构有从菱方钙钛矿向斜方转变的趋势,且样品电容率大幅度增大, 而介电损耗也略有增加;在测试频率为10 4 Hz条件下, BiFe 0.85Mn 0.15O 3 ( εr=1065)的 εr是纯BiFeO 3 ( εr=50.6)的22倍; 掺杂后样品的铁电极化性能均有不同程度的提高,可能是由于Mn 4+稳定性优于 Fe 3+,高价位Mn 4+进行B位替代改性BiFeO 3陶瓷, 能减少Bi 3+挥发,抑制Fe 3+价态波动,从而降低氧空位浓度,减小样品的电导和漏电流. 相似文献
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