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1.
Deng Xiangyun Wang Xiaohui Li Dejun Li Longtu 《Frontiers of Materials Science in China》2007,1(3):316-318
The density of states and band structure of 20 nm barium titanate (BaTiO3, BT) ceramics are investigated by first-principles calculation. The full potential linearized augmented plane wave (FLAPW)
method is used and the exchange correlation effects are treated by the generalized gradient approximation (GGA). The results
show that there is substantial hybridization between the Ti 3d and O 2p states in 20 nm BT ceramics and the interaction between
barium and oxygen is typically ionic. 相似文献
2.
We have synthesized nickel (Ni) and iron (Fe) ion doped BaTiO3 nanoparticles through a chemical route using polyvinyl alcohol (PVA). The concentration of dopant varies from 0 to 2 mole%
in the specimens. The results from X-ray diffractograms and transmission electron micrographs show that the particle diameters
in the specimen lie in the range 24–40 nm. It is seen that the dielectric permittivity in doped specimens is enhanced by an
order of magnitude compared to undoped barium titanate ceramics. The dielectric permittivity shows maxima at 0.3 mole% doping
of Fe ion and 0.6 mole% of Ni ion. The unusual dielectric behaviour of the specimens is explained in terms of the change in
crystalline structure of the specimens. 相似文献
3.
Jinseong KimDowan Kim Taimin NohByungmin Ahn Heesoo Lee 《Materials Science and Engineering: B》2011,176(15):1227-1231
The co-doping characteristics on microstructure and thermal properties of barium titanate (BaTiO3) were investigated to elucidate formation of core-shell structure by dysprosium (Dy) and thulium (Tm) addition in the BaTiO3-Dy2O3-Tm2O3 system. The dielectrics co-doped with 0.7 mol% Dy2O3 and 0.3 mol% Tm2O3 had the dielectric constant up to 2200 as a function of temperature, which was 30% higher than that of specimen containing only Tm2O3 at the room temperature. It could be explained by the fact that the increase of Dy2O3 addition contributed to the improvement of dielectric constant. On the other hand, the rapid diffusion rate of Dy3+ ions in BaTiO3 showed an adverse effect on temperature stability caused by destruction of core-shell. As the compensation for shell expansion in BaTiO3, the reinforcement of the core-shell structure through the addition of Tm2O3 was confirmed by TEM-EDS analysis and attributed the temperature coefficient of capacitance (TCC) in a reliability condition (−55 °C to 125 °C, △C = ±15% or less). The enhanced electrical properties and temperature stability could be deduced from the generation of electrons and the formation core-shell structure in co-doped BaTiO3 system respectively. 相似文献
4.
Shunqi Gao Shunhua WuYonggang Zhang Hongxing YangXinru Wang 《Materials Science and Engineering: B》2011,176(1):68-71
This paper investigated the microstructure and dielectric properties of BaTiO3-Pb(Sn, Ti)O3 system ceramics. The Curie point of BaTiO3 is 130 °C. When the temperature is higher than 130 °C, the dielectric constant of BaTiO3 drops severely according to Curie-Weiss law. Pb(Ti, Sn)O3(PTS) was selected to compensate the dielectric constant doping of BaTiO3 since it has high Curie temperature (Tc) point that is about 296 °C. The Curie temperature (Tc) point of BaTiO3 was broadened and shifted to higher temperature because of the doping of PTS, so the temperature coefficient of capacitance (TCC) curves of the ceramics based on BaTiO3 was flattened. When 2 wt% Pb(Ti0.55Sn0.45)O3 was added, the sample showed super dielectric properties that the dielectric constant was >1750 at 25 °C, dielectric loss was lower than 2.0% and TCC was <±10% from −55 °C to 200 °C. Therefore the materials satisfied EIA X9R specifications. 相似文献
5.
Tomasz M. StawskiWouter J.C. Vijselaar Ole F. GöbelSjoerd A. Veldhuis Brian F. SmithDave H.A. Blank Johan E. ten Elshof 《Thin solid films》2012,520(13):4394-4401
Thin films of barium titanate (BTO) of 200 nm thickness, derived from an alkoxide-carboxylate sol-gel process, were deposited on Pt/Ti and SrRuO3/ZrO2-8%Y2O3 coated Si wafers. Films with a dense columnar microstructure were obtained by repeated deposition of thin amorphous layers from low-concentrated sols, and crystallization at 800 °C. This method added 10 nm thickness to the crystalline BTO film in each deposition step. The harsh processing conditions had a negative impact on the platinized silicon wafers, where Pt-Si silicides were formed. This led to diffusion of Si into BTO and interfacial silicate formation. The interfacial silicate layer was the cause of deteriorated dielectric and ferroelectric properties of the BTO layer. Use of SrRuO3/ZrO2-8%Y2O3/Si substrates solved the problem. No diffusion of Si was observed, and BTO films with good dielectric and ferroelectric properties were obtained. 相似文献
6.
晶粒可控钛酸钡致密陶瓷的制备及表征 总被引:2,自引:0,他引:2
采用超重力反应沉淀法制备的纳米钛酸钡粉体和常规陶瓷工艺,通过控制烧结温度在 1200 ~1300℃,分别制备了晶粒尺寸 0.45~2.2μm的致密陶瓷。实验结果表明超重力反应沉淀法制备的粉体具有良好的烧结和介电性能。烧结温度为 1200℃时,相对密度即可达到95%,晶粒尺寸为 0.45μm,随烧结温度的升高,晶粒逐渐长大,未出现晶粒的异常长大现象,到1300℃相对密度和晶粒尺寸分别达到 97.7%和2.2μm。钛酸钡陶瓷介电性能有明显的粒度效应,晶粒在1.2μm左右时,室温介电常数达到最大(4143)。由于晶粒内部立方相成分的出现,包含更细晶粒的陶瓷(d=0.45μm)呈现低的介电常数。 相似文献
7.
Influence of gamma irradiation on the refractive index of Fe-doped barium titanate thin films 总被引:1,自引:0,他引:1
Polycrystalline Fe-doped barium titanate (Fe-doped BaTiO3) thin films were grown by thermal decomposition of the precursors deposited from a sol-gel system onto quartz substrates. The changes in the transmittance spectra induced by gamma irradiation on the Fe-doped BaTiO3 thin films were quantified. The values for the optical energy band gap were in the range of 3.42-3.95 eV depending on the annealing time. The refractive index of the film, as measured in the 350-750 nm wavelength range was in the 2.17-1.88 range for the as prepared film, and this increased to 2.34-1.95 after gamma irradiation at 15 kGy. The extinction coefficient of the film was in the order of 10−2 and increased after gamma irradiation. We obtained tuneable complex refractive index of the films by exposure to various gamma rays doses. 相似文献
8.
采用传统固相法制备了(1-x)BiScO3-xPbTiO3(BSPT)(x=0.58~0.66)铁电陶瓷.经XRD分析发现,BSPT体系三方相和四方相的准同型相界(MPB)在x=0.62附近.在准同型相界附近x=0.62处BSPT陶瓷的压电常数d33和平面机电耦合系数kp具有极大值,但机械品质因素Qm却最小.对BSPT体系及其它钙钛矿型ABO3化合物的结构稳定性进行了讨论,发现容差因子t和离子键百分比p可作为判定钙钛矿结构形成难易程度的基本参数,容差因子t越接近1且离子键百分比p越大的化合物,越容易合成稳定的钙钛矿结构. 相似文献
9.
(K0.5Na0.5)NbO3 (KNN) and 0.995(K0.5Na0.5)NbO3-0.005AETiO3 (AE = Mg, Ca, Sr, Ba) were successfully prepared by conventional ceramic processing and without the cold-isostatic-pressing (CIP) process. The effects of low AETiO3 (AET) concentration on crystal structure, density, dielectric and piezoelectric properties of the KNN based ceramics were evaluated. The results show that adding MgTiO3(MT) and BaTiO3(BT) to KNN can lead to the appearance of a trace amount of second phase(s), reduced density and deteriorated electrical properties. Adding CaTiO3(CT) and SrTiO3(ST) to KNN can promote densification and optimize electrical properties. Two phase transitions at Tt-o ( the temperature at which the phase transition from orthorhombic to tetragonal occurs) and Tc (the Curie temperature) were observed in KNN and all KNN-AET ceramics, by using differential scanning calorimetry (DSC) analysis and dielectric characterization. Adding AET to KNN caused the variations of Tt-o and Tc. 相似文献
10.
采用传统陶瓷工艺制备了钙钛矿型低铅压电陶瓷xPbTi0.4716Zr0.4834(Mn1/3Sb2/3)0.0450O3-(1-x)(K0.485Na0.485Li0.03)NbO3[xPMS-(1-x)KNLN],研究了该陶瓷体系的结构和介电、压电与铁电性能以及这些结构和性能与工艺条件的关系。XRD分析表明,随着烧结温度的升高,陶瓷晶相由焦绿石相与赝立方钙钛矿相共存转变为单一的四方钙钛矿相;SEM分析表明,在烧结过程中产生了以(K0.485Na0.485Li0.03)NbO3组分为主的液相,并在烧结温度提高的过程中产生孔洞出现-孔洞消失的现象;电学测试表明,xPMS-(1-x)KNLN陶瓷具有良好的性能,在x=0.75、烧结温度为1250℃时,陶瓷的性能参数为压电常数d33=182pC/N,机电耦合系数kp=34.5%,居里温度TC=165℃,剩余极化强度Pr=21.2μC/cm2,矫顽场强Ec=1.47kV/mm,介电常数εr=1879,介电损耗tanδ=0.92%。 相似文献
11.
钛酸锶钡(BSTO)铁电陶瓷材料的介电常数随外加直流电场的变化呈现非线性特性.纯BSTO材料由于较高的介电常数和较大的介电损耗不能满足移相器介质材料的要求.通过在BSTO中添加Y2O3来改善BSTO铁电陶瓷材料的介电性能.研究结果是:(1)在BSTO体系中微量掺杂Y2O3,Y3 以取代Ba2 的方式存在于钙钛矿的晶格中,形成均匀的固溶体Ba0.5-xYxSr0.5TiO3;(2)随Y3 添加量的增加,居里峰逐渐变宽,峰高逐渐降低,相变弥散效应增强;(3)Y3 的掺杂能促进BSTO陶瓷的致密化烧结,并显著降低BSTO陶瓷的介电常数. 相似文献
12.
13.
用传统固相烧结工艺,制备了纯相的Bi4Ti3O12 (BTO)陶瓷,A位掺杂的Bi3.25La0.75Ti3O12(BLT),Bi3.15Nd0.85Ti3O12(BNdT)铁电陶瓷.X射线衍射结果表明,所有样品均为单一的层状钙钛矿结构,La、Nd掺杂未改变BTO的晶体结构.铁电测试结果表明,BTO、BLT和BNdT陶瓷的剩余极化2Pr值分别为12.4、23.8和39.4μC/cm2.A位掺杂后,BLT、BNdT的2Pr值比未掺杂的BTO分别提高了1.92和3.18倍.漏电流测试表明,BLT、BNdT陶瓷的漏电流密度比BTO明显降低.A位掺杂显著提高了BTO陶瓷的铁电性能. 相似文献
14.
Qihua Yang Liang Fang Fengang Zheng Mingrong Shen 《Materials Chemistry and Physics》2009,118(2-3):484-489
The structural, electrical, luminescent, and magnetic properties of Eu3+-doped Ba0.77Ca0.23TiO3 (BCT23:Eu) ceramics were investigated in this paper. Three different incorporation mechanisms of Eu3+ were realized in BCT23 by considering different charge compensation mechanisms: (i) Ca site substitution with Ca vacancy compensation; (ii) Ti site substitution with O vacancy compensation; (iii) simultaneous substitution at both Ca and Ti sites with self-compensation. Besides the evident ferroelectric properties, the BCT23:Eu ceramics showed the photoluminescence and paramagnetic properties, implying that they can be considered as the multifunctional materials. Both the electric and luminescent properties were sensitive to the Eu doping concentrations and positions, due to the variations of the microstructures and different charge compensation mechanisms. 相似文献
15.
A microwave ceramic with general composition (1-x-y) BaTiO3 + x Cr2Ti3O9 + y Bi2O3 has been prepared by solid state synthesis at 1300-1400 °C. The phase composition, perovskite structural parameters and dielectric properties have been obtained by X-ray diffraction and dielectric measurements as a function of chemical composition and temperature. At low doping levels the formation of BaTiO3-based solid solution has been found. The precipitation of BaCrO3 has been detected at x = y = 2.0 mol%. A model of the incorporation of Cr3+ and Bi3+ ions into BaTiO3-based crystal lattice has been proposed. Diffused phase transition in the temperature range 100-140 °C have been revealed by dielectric measurements for different ceramic composition. As high dielectric constant as 7311 and as low dielectric loss as 0.02 have been found for the composition of 0.98BaTiO3-0.01Cr2Ti3O9-0.01Bi2O3. 相似文献
16.
《Virtual and Physical Prototyping》2013,8(4):371-381
ABSTRACTAl2O3-based composite ceramics have excellent high temperature performance and are ideal materials for preparing hot end components. However, poor fracture toughness and thermal shock resistance limit its applications. Based on the excellent low thermal expansion characteristics and thermal shock resistance of Al2TiO5 ceramic, different composition ratios of Al2O3/Al2TiO5 composite ceramics were prepared by directed laser deposition (DLD) technology. Effects of TiO2 doping amount on microstructure and properties of the composite ceramics were investigated. Results show that α-Al2O3 phase is discretely distributed in the continuous aluminum titanate matrix when TiO2 doping amount between 2 and 30?mol%. With the increase of TiO2 doping amount, content of Al2O3 gradually decreases and its morphology changes from cellular to dendritic. When TiO2 doping amount reaches 43.9?mol%, the microstructure transforms into fine Al2TiO5/Al6Ti2O13 eutectic structure. Property test results show that Al2O3/Al2TiO5 composite ceramics have good comprehensive mechanical properties when TiO2 doping amount between 2 and 6?mol%. 相似文献
17.
100nm是介于微米晶和纳米晶之间的重要临界尺寸,研究了平均晶粒尺寸为100nm的钛酸钡(BTO)陶瓷的微结构和铁电性能,分析了测试温度和外加电场对纳米晶钛酸钡陶瓷铁电性的影响。与超细纳米晶BTO陶瓷不同的是,100nm BTO陶瓷主要以四方相形式存在的;介电温谱显示,正交到四方相的相变具有典型的弥散特征,低温时介电损耗<0.02。此外,铁电性能测试表明,100nm BTO陶瓷具有良好的铁电滞后特征,随着电场的增加,能量损耗密度、剩余极化强度和矫顽场均增加;随着温度的升高,陶瓷的铁电性在逐渐减弱,高于居里温度时由铁电相转为顺电相,铁电性消失。实验结果表明,100nm BTO陶瓷的铁电性与测试温度和外加电场有着密切的关系。 相似文献
18.
19.
X.W. WangX. Wang W.J. GongY.Q. Zhang Y.L. ZhuZ.J. Wang Z.D. Zhang 《Thin solid films》2012,520(7):2785-2788
BaTiO3 films were epitaxially grown on SrTiO3 (001) substrates buffered with SrRuO3 films as bottom electrode by pulsed laser deposition under high oxygen pressure of 30 Pa. The quality of the BaTiO3/SrRuO3/SrTiO3 multilayer films was analyzed by means of X-ray diffraction, atomic force microscopy and transmission electron microscopy. BaTiO3 films were found to be highly c-axis-oriented tetragonal phase with c/a = 1.002. The dielectric constant first increased with increasing temperature, and showed a peak at the Curie temperature of about 356 K. The films had well-saturated hysteresis loops with a remnant polarization of 7.3 μC/cm2 and a coercive field of 29.5 kV/cm at room temperature. 相似文献
20.
Thermal expansion data is reported over a wide temperature range (80–800 K) for BaTiO3 (BT) and Pb(Fe1/2 Nb1/2)O3 (PFN), belonging to different classes of the ferroelectric materials. The sharp structural phase transitions of BT result
in lowering of the thermal expansion coefficient (α) at the transitions which is proportional to the change in polarization
at the transitions. In PFN, a relaxor ferroelectric, lowering of α is spread over a wider temperature range across the dielectric
maxima. 相似文献