Bi4Ti3O12掺杂对(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7陶瓷结构与介电性能的影响

研究了Bi4Ti3O12掺杂对(Bi1.5Zn0.5)(Zn0.5Nb1.5)O7(BZN)陶瓷烧结特性、相结构和介电性能的影响.采用传统的固相反应法制备样品,X射线衍射技术分析相结构,SEM观察表面形貌.结果表明,Bi4Ti3O12掺杂能有效地促进烧结,提高介电常数ε,降低介电损耗tgδ,优化介电频率温度系数αε.1000℃烧结8%(摩尔分数) Bi4Ti3O12掺杂的BZN陶瓷具有较好的介电性能ε=192,tgδ= 4.21×10-4,αε=-3.37×10-4/℃.     

A位掺杂Bi4Ti3O12陶瓷的铁电性能研究

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.     

Effect of Co3+ on structure and electrical properties of Na0.5Bi2.5Nb2O9 ceramics

Journal of Materials Science: Materials in Electronics - Na0.5Bi2.5Nb2-xCoxO9 (NBNC-x, x?=?0.00, 0.02, 0.05, 0.07, 0.09) bismuth layered piezoelectric ceramics were synthesized by the...     

Effects of Pr6O11 doping on the microstructures and properties of Bi4Ti3O12 ferroelectric ceramics

Effects of Pr₆O₁₁ doping on the microstructures and the electrical properties of Bi₄Ti₃O₁₂ (BIT) were investigated using dense ceramics, which were prepared by a conventional ceramic technique. For all the samples, X-ray diffraction (XRD) analyses revealed Bi-layered perovskite structures, and the scanning electron microscope (SEM) micrographs showed well developed plate-like morphologies with random orientations. The P–E hysteresis loop of samples measured at room temperature exhibited a large remnant polarization and a low coercive field. In addition, the DC current–voltage properties measured at different temperature from RT to 550 °C were discussed. Results indicate that Pr₆O₁₁ can be a good additive to improve the properties of Bi₄Ti₃O₁₂.     

锰掺杂对PbZr0.5Ti0.5O3铁电薄膜电学性能的影响

采用Sol-gel方法在生长有LNO3的Si(100)衬底上制备了掺Mn的PbZr0.5Ti0.5O3铁电薄膜(PMZT)。PMZT薄膜具有优良的铁电性。在外加电场下观察到了非对称剩余极化翻转行为。这种剩余极化的翻转不对称随着锰掺杂浓度的增加而变大,从而表明极化过程中产生的内建偏压电场是由Mn的掺杂引起的。当薄膜厚度保持不变时候,PMZT薄膜的剩余极化(Pr)和平均矫顽电场(Ec)随着锰掺杂浓度的增大而减小。在低频下,PMZT薄膜的介电常数随着锰的掺杂浓度的增加而减小。瞬时电流随着时间的呈指数衰减,最后到达饱和的稳态值。样品的漏电流密度随着电压的增加而近似地线性增加,显示出欧姆特性。在相同电压下,漏电流密度随着Mn掺杂浓度的增加而增加。     

Sintering and characterization of Bi4Ti3O12 ceramics

Polycrystalline ferroelectric Bi₄Ti₃O₁₂ ceramics have been prepared by the method of reactive liquid phase sintering. The sintering behaviour of the Bi₂O₃-TiO₂ composite was examined by plotting the isothermal densification curves. The results indicate that the starting oxides are involved in the reaction even at temperatures lower than or equal to 800°C, but the reaction advances at a very slow rate. Above solidus, the liquid phase promotes an extended reaction. Saturation observed in two densification curves, at 875 and 1100°C demonstrate that the reaction proceeds by two steps. A completion of the Bi₄Ti₃O₁₂ formation occurs after 60 min of sintering at 1100°C. Optical micrographs of sintered bismuth titanate ceramics show randomly oriented ferroelectric grains separated by a paraelectric intergranular layer. The Bi₄Ti₃O₁₂ crystallites exhibit a platelike morphology, similar in the appearance to mica, as evidenced by scanning electron micrographs. Isothermal annealing (750 to 950°C) does not affect the microstructure and electric properties of sintered bismuth titanate. The considerable value of dielectric permittivity and the appearance of hysteresis have been correlated to the presence of oxygen vacancies within the pseudotetragonal structure of Bi₄Ti₃O₁₂. The oxygen vacancies are preferentially sited in the vicinity of bismuth ions as evidenced by X-ray photoemission data. XPS and AES measurements confirm that the surface concentration of cations comprising the Bi₄Ti₃O₁₂ ceramics does not deviate from the nominal bulk composition.     

La掺杂对Sr2Bi4Ti5O18铁电陶瓷性能的影响

利用传统的固相烧结工艺制备了Sr2LaxBi1-xTi5O18(x=0．00、0．05、0．1、0．25、0．5、0．75、1．00)陶瓷样品。用X射线衍射对其微结构进行了分析．并测量了其铁电、介电性能。X射线衍射结果表明La掺杂对Sr2Bi4TixO18的晶体结构几乎没有影响。样品的铁电、介电结果表明。随着La掺杂量的增加，样品的剩余极化(2Pr)和矫颈场(Ec)逐渐减小。这是由于离子半径较大的La取代类钙钛矿层A位Bi离子。使得样品晶格畸变变小，从而导致2Pr降低。晶格畸变的减小也使得沿着外电场方向氧八面体中的阳离子更易运动。导致Ec减小。样品的相变温度L随着La含量的增加而降低。这也与样品晶格畸变有关。     

Microstructure and electrical properties of LaMnO3-CaCu3Ti4O12 composite ceramics

In this study, xLaMnO₃-(1???x)CaCu₃Ti₄O₁₂ (0?≤?x?≤?0.7) composite ceramics have been prepared by the conventional solid-state method. XRD results show that the composite ceramics are mainly composed of LaMnO₃ and CaCu₃Ti₄O₁₂ phases. Electrical property analysis shows that the resistivity ρ₂₅ gradually decreases from 2.17?×?10⁸ to 1.74?×?10⁵ Ω·cm with increasing LaMnO₃ content. The relationship between lnρ and 1000/T is not linear and changes around 350 °C. In the temperature range of 0–350 °C, the activation energy Ea_0–350 °C decreases gradually with the increase of the LaMnO₃ content. In the temperature range of 350–500 °C, the activation energy Ea_{350–500 °C} increases first and then decreases, which is related to the variation of oxygen vacancy. The compounding of LaMnO₃ gives rise to the decrease in B value, thus, providing the potential for the applications of wide temperature range thermistors. After annealing, the coefficient of aging (ΔR/R) of the composites decreases from 23.73 to 3.01%.

     

Ti4+取代Zn2+、Nb5+对Bi2O3-ZnO-Nb2O5系介质材料结构和性能的影响

研究了Ti4 取代Zn2 ,Nb5 对Bi2O3-ZnO-Nb2O5系介质材料结构和性能的影响，研究表明，少量替代对于材料的结构和性能没有太大的影响；随着替代量的增加，相结构中出现正交Bi4Ti3O12相；微观形貌中出现棒晶，介电常数逐渐增大，温度系数逐渐向负温度系数方向移动，适量Ti4 替代可以获得性能很好的NP0介质材料。     

Sandwiched BaNd2Ti4O12/Bi4Ti3O12/BaNd2Ti4O12 ceramics prepared by spark plasma sintering

Spark plasma sintering (SPS) combined with heat treatment was investigated to prepare laminated ceramics from compositions having quite different sintering temperatures. Although the optimal sintering temperature of BaNd₂Ti₄O₁₂ (BNT) ceramics was much higher than that of Bi₄Ti₃O₁₂ (BIT) ceramics, sandwiched BaNd₂Ti₄O₁₂/Bi₄Ti₃O₁₂/BaNd₂Ti₄O₁₂ (BNT/BIT/BNT) composite ceramics were successfully prepared with this new method. The results of scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) showed that the BNT layers and the BIT layer were well bonded and no significant diffusion between them was observed. The temperature coefficient of dielectric constant of the laminated ceramic was found to be much smaller than that of BNT ceramic.     

Effects of Nb5+ doping on sintering and electrical properties of lead-free (Bi0.5Na0.5)TiO3 ceramics

The Nb⁵⁺ doped (Bi_0.5Na_0.5)TiO₃ (BNT) ceramics were manufactured by a conventional solid state reaction method. The influence of Nb⁵⁺ doping on the sintering, microstructure and various electrical properties of BNT ceramics was investigated. The results of X-ray diffraction show that the solubility limit of Nb⁵⁺ in the BNT lattice is less than 3%. Additionally, Nb⁵⁺ doping produces significant effects on the densification and grain growth of BNT ceramics. Various electrical properties of BNT ceramics are obviously changed with doping a small amount of Nb⁵⁺. The ferroelectric and piezoelectric properties display enhanced values at a low doping level. The formation of A-site vacancies is considered as the reason for the changed ferroelectric and electromechanical behavior.     

La掺杂的Bi4Ti3O12陶瓷的动态变温X射线衍射研究

利用动态变温X射线衍射技术,研究了La掺杂Bi4Ti3O12（BLT）陶瓷相的形成过程、微结构的变化及其与温度的关系。动态跟踪比较了不同物相的反应速率与消长规律。比较了大气与真空不同的气氛环境对BLT相结构形成的影响。初步给出了固态成相的温度范围和所需时间。     

Effects of a Bi2Ti2O7 seeding layer on properties of Bi3.5Nd0.5Ti3O12 thin film

A thin-film bilayer structure consisting of polycrystalline Bi_0.5Nd_0.5Ti₃O₁₂ (BNdT) and preferential (111)-orientated Bi₂Ti₂O₇ (BTO) has been prepared on n-type Si (100) substrate by a chemical solution deposition and spin-coating technique. The crystallization of BNdT film can be enhanced and the surface consists of larger grains because of the intervention of BTO. We fabricated the Au/BNdT/BTO/Si and Au/BNdT/Si structures, respectively. Compared with BNdT, the BNdT/BTO film shows better insulating and memory properties. The room temperature resistivity is 10¹¹ Ω cm at a dc bias of 5 V. The C–V hysteresis curve is referred to as polarization-type switching and the memory window is about 3 V. All these results show that the BTO is an effective diffusion-barrier and plays a brilliant role as a seeding layer.     

Effect of co-substitution of Na0.5Bi0.5TiO3 and CaTiO3 on the structure and properties of BiFeO3 ceramics

Journal of Materials Science: Materials in Electronics - Ion substitution was the most efficient way for BiFeO3 modification. In this work, polar Na0.5Bi0.5TiO3 and non-polar CaTiO3 were chosen to...     

Fabrication and dielectric properties of Na0.5Bi0.5Cu3Ti4O12/poly(vinylidene fluoride) composites

Na_0.5Bi_0.5Cu₃Ti₄O₁₂ (NBCTO)/poly(vinylidene fluoride) (PVDF) composites with various NBCTO volume fractions were prepared via solution mixing and hot pressing process. The structure, morphology, and dielectric properties of the composites were characterized with X-ray diffraction (XRD), thermal-gravimetric analysis (TGA), scanning electron microscope (SEM), and broadband dielectric spectrometer. The dielectric constant (ε) and dielectric loss (tan δ) of the composites were both found to increase with increasing NBCTO volume fraction within the frequency range of 1–10⁶ Hz at room temperature. Relatively high dielectric constant of 79.8 and low loss of 0.21 at 1 kHz were obtained for the NBCTO/PVDF composite with 50 vol% NBCTO. Additionally, theoretical models like Logarithmic mixture rule, Maxwell–Garnet, Effective medium theory, and Yamada model were also employed to predict the dielectric constant of these composites. The values obtained by the EMT model are in close agreement with the experimental values.