Structural,dielectric, impedance and ferroelectric properties of lead-free Bi(Fe0.85Dy0.15)O3 ceramic

Nowadays, several research groups are extensively trying to develop by synthesizing and characterizing single/co-doped single-phase bismuth ferrite (BFO) in order to get a highly efficient eco-friendly multifunctional devices. In this process, this report is an attempt to provide the detailed studies of structural, dielectric, impedance and ferroelectric properties of Bi(Fe_0.85Dy_0.15)O₃ ceramic fabricated via the solid-state reaction method. Analysis of X-ray diffraction (XRD) data confirms a single phase of orthorhombic symmetry. The average crystallite (particle) size is found to be in the order of?~?41 nm. The field emission scanning electron microscopy (FE-SEM) spectrum shows a homogeneous grain distribution of the sample. The elemental composition examined by means of energy dispersive X-ray spectroscopy (EDXS) shows the existence of constituent elements of the sample. The electrical measurements and analysis, carried out using a computer-controlled phase sensitive multimeter (PSM) in a frequency range of 1 kHz–1 MHz at different sets of temperature (25–325 °C), provide many interesting features to explain further conduction mechanism. The dielectric analysis exhibits high value of dielectric constant (?_r) and small value of dielectric loss (tanδ). Due to the effect of electronic and space charge polarization, the ?_r value falls with an increasing frequency. The frequency–temperature dependence of impedance and electrical modulus analysis reveals the presence of semiconductor nature and non-Debye type of relaxation process in the sample. The analysis of ac-conductivity (σ_ac) with respect to frequency and temperature obeys the universal Jonscher’s power law. The electric polarization study shows an enhancement in ferroelectric property of the material. Hence, based on the significant enhancement in electrical and ferroelectric properties of the Bi(Fe_0.85Dy_0.15)O₃ material, the material may be considered for some applications.

     

Intrinsic dielectric properties and lattice vibrational characteristics of single phase BaTiO3 ceramic

Journal of Materials Science: Materials in Electronics - A single phase BaTiO3 ceramic was prepared by traditional solid-state sintering process at 1220 °C for 4 h. XRD...     

Effect of the dispersibility of BaTiO3 nanoparticles in BaTiO3/polyimide composites on the dielectric properties

We have investigated the effect of coupling agents with different organic moiety on the dielectric properties of polyimide/BaTiO₃ (70 nm) composite films. INAAT (isopropyl tris(N-amino-ethyl aminoethyl)titanate, KR 44) and APTS (3-amino-propyl-triethoxysilane) were used as coupling agents, respectively, for homogeneous dispersion of BaTiO₃ particles into a polyimide matrix. The composite films were prepared by pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA)-based polyimide. Enhanced dispersion of BaTiO₃ particles was obtained by the use of INAAT with more organic moiety compared to that afforded by APTS. The polyimide composite with BaTiO₃ particles (BaTiO₃ content at 50 vol.%) treated by INAAT showed an increased dielectric constant of 19.03 while retaining an appropriate dielectric loss of 0.0109, as compared to the dielectric constant (14.64) of polyimide/APTS-treated BaTiO₃ composite. The results of this work demonstrate the potential use of an INAAT coupling agent with more organo functional groups for obtaining enhanced dielectric properties in a polyimide/BaTiO₃ composite for application in an embedded capacitor.     

Measurement and modeling of dielectric properties of Pb(Zr,Ti)O3 ferroelectric thin films

In this study, the real and imaginary parts of the complex permittivity of lead zirconate titanate ferroelectric thin films are studied in the frequency range of 100 Hz to 100 MHz. The permittivity is well fitted by the Cole-Cole model. The variation of the relaxation time with the temperature is described by the Arrhenius law and an activation energy of 0.38 eV is found. Because of its nonlinear character, the dielectric response of the ferroelectric sample depends on the amplitude of the applied ac electric field. The permittivity is composed of three different contributions: the first is due to intrinsic lattice, the second is due to domain wall vibrations, and the third is due to domain wall jumps between pinning centers. This last contribution depends on the electric field, so it is important to control the field amplitude to obtain the desired values of permittivity and tunability.     

Effect of KNN doping on the dielectric properties of BaTiO3 lead-free ceramics

Journal of Materials Science: Materials in Electronics - In this study, the phase structure, microstructure, and dielectric properties of BT-xKNN ceramic prepared by traditional solid-phase method...     

The ageing of a BaTiO3 dielectric containing both ferroelectric and paraelectric components

A BaTiO₃ composition with a high ageing rate of permittivity and demonstrating a downward bend in its permittivity versus log time characteristic is studied. Models which assume ageing and non-ageing components in series or series/parallel configurations reproduce the characteristic and indicate an initial permittivity exceeding 5000 for the ageing component at a temperature 40 K below its Curie point.     

双马来酰亚胺/钛酸钡复合材料介电性能的研究

以双马来酰亚胺（BMI）为树脂基体，压电陶瓷BaTiO，为功能填料，采用浇铸的方法制备了BMI/BaTiO3复合材料。考察了复合材料的介电性能，并用多种混合法则对复合材料的介电常数进行拟合分析。研究结果表明，BaTiO3含量的增加提高了材料的介电常数，同时增加了材料的介电损耗；BMUBaTiO3复合材料的介电性能具有良好的频率稳定性：使用Lichterecker混合规则的拟合结果与实验测试结果具有很好的一致性。     

Phosphor-doped BaTiO3: Microstructure development and dielectric properties

The phosphor cation retards BaTiO₃ formation during the first reaction stage, and favours Ba₂TiO₄ formation. As a consequence, the end of the reaction is only accomplished at 1150 °C. The average particle size of the synthesized powder, after attrition milling was <1.0 m. Isopressed bars were sintered from 1200–1400 °C. Dilatometric measurements showed the existence of two sintering mechanisms; these were confirmed by means of isothermal sintering experiments. Microstructural development at low sintering temperature differs from that corresponding to higher ones. Very high permittivity values were measured in the 1325–1350 °C sintered samples. This anomalous dielectric behaviour is associated with the presence of phosphor.     

Effect of synthesized BaTiO3 doping on the dielectric properties of ultra temperature-stable ceramics

The high performance X9R ceramics could be sintered at as low as 1,120?°C by doping 3?mol% synthesized BaTiO₃ (SB) additives into the BaTiO₃-based ceramics, with a dielectric constant greater than 2,200 at 25?°C and dielectric loss lower than 1.7?%. The effects of SB additives on the microstructure and dielectric properties of BaTiO₃-based ceramics were investigated. The dielectric constant of BaTiO₃-based ceramics doped with 3?mol% SB was increased due to the promotion of the densification of ceramics. With SB content up to 4.5?mol%, Ti⁴⁺’s polarization was depressed, which resulted in the decrease of augmented dielectric constant at 25?°C. The partial solid solution was formed between Pb(Ti, Sn)O₃ and BaTiO₃, and the substitutions of Pb at A-sites and Sn at B-sites were existed. The strengthen of Ti–O bonds and higher Curie point of Pb(Ti_0.55Sn_0.45)O₃ was helpful to increased the Curie point of the ceramics effectively. Doped with SB additives, the volume of ferroelectric core was increased, and the sharp peak intensity at Curie point was increased accordingly. Capacitance temperature characteristics was improved attributed to the mutual effects of SB and Pb(Ti_0.55Sn_0.45)O₃. The formation of core–shell structure was sensitive to the sintering temperature, so the dielectric properties of ceramics were highly depended on the sintering temperature.     

The study of CoFe2O4/Ba0.85Ca0.15Zr0.1Ti0.9O3-laminated composite ceramic on dielectric,relaxation, ferroelectric,and magnetoelectric coupling properties

Journal of Materials Science: Materials in Electronics - In this work, pure Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) and CoFe2O4 (CFO) ceramics were prepared by the sol–gel and co-precipitation...     

Microstructure development and dielectric properties of fast-fired BaTiO3 ceramics

The technique of zone sintering was applied to three BaTiO₃ source materials; studies were made in air, oxygen and vacuum. The optimum firing conditions suggested for the zone sintering of these materials were a temperature of 1450° C and a time in the hot zone of 5 min. The temperature dependence of the dielectric constant could be closely related to the firing conditions and material microstructure. Lower room-temperature dielectric constants and lower Curie temperatures were found as the holding time in the hot zone was increased, yielding larger grained structures.     

Effect of silane as coupling agent on the dielectric properties of BaTiO3-epoxy composites

The influence of silane coupling agents on the microstructure and dielectric behaviour of epoxy/BaTiO₃ composites was studied. Epoxy was diluted using tetrahydrofuran as solvent in order to facilitate the mixing step. Methoxy silane was applied onto ceramic particles. Different diluted aqueous solutions with 0.25, 0.35 and 0.50 wt% of silane/BaTiO₃ were used. Dipping technique was utilised to obtain composite films. Dielectric measurements were performed from 25 Hz to 1 MHz and from 20 °C to 120 °C. Composites presented good dielectric properties and a strong dependence with the silane concentration.     

Effect of Zr substitution on structural and dielectric properties of Pb5EuTi3−xZrxNb7O30 (x=0, 1, 2 and 3) ferroelectric ceramics

The polycrystalline samples of Pb₅EuTi_3–x Zr _x Nb₇O₃₀ (x=0, 1, 2 and 3) were prepared by a high-temperature solid-state reaction technique. Formation of the compounds was checked by X-ray diffraction method. All the compounds were found to have orthorhombic structure at room temperature. Studies of their dielectric constant (e) as a function of temperature (25–375 °C) at 10 kHz exhibit ferroelectric phase transition of a diffuse-type. With increasing Zr concentration (x), transition temperature (T_c) as well as dielectric constant decreases. Temperature variation of d.c. resistivity/conductivity shows that these compounds exhibit negative temperature coefficient of resistance in the high temperature range.     

Pyroelectric and dielectric bolometer properties of Sr modified BaTiO3 ceramics

The pyroelectric and dielectric bolometer properties of Sr modified BaTiO₃ ceramics were investigated for thermal IR detector applications. The (Ba_1–x, Sr_x)TiO₃ solid solution ceramics have been prepared by adding 10–40 at % SrTiO₃ to BaTiO₃ and with different sintering conditions and under dc fields. The relationships of processing parameters, microstructures, dielectric/pyroelectric properties and dc fields are discussed. And the figures of merit are compared between pyroelectric-type and dielectric bolometer-type IR sensors based on the experimental results.     

Fast-sintering of hydrothermally synthesized BaTiO3 powders and their dielectric properties

Hydrothermally synthesized barium titanate (BaTiO₃) powders with a submicrometre particle size have been fast-sintered with a heating rate of ∼ 200 °C min^-1 at various temperatures (1250–1350 °C) for short times (5 and 15 min). The microstructures and dielectric properties of the sintered samples are studied and compared with those sintered conventionally. The sample fast-sintered at 1250 °C for 5 min had the highest dielectric constant value of approximately 3700 with an average grain size of about 1 μm. Both the dielectric constant and the Curie–Weiss temperature are found to be dependent on the grain size of the sintered samples, particularly when the average grain size is less than 5 μm. This has been attributed to the presence of internal stress in the fine-grained BaTiO₃. This revised version was published online in November 2006 with corrections to the Cover Date.     

表面态对纳米晶BaTiO3介电性能的影响

采用硬脂酸凝胶法制备了粒度均匀的纳米晶BaTiO3，用X射线衍射分析、红外光谱分析、透射电子显微镜对产物进行了表征，研究了表面态与介电性能。结果表明，BaTiO3纳米材料表面的不完整性主要是氧空位造成的，暴露在粒子表面的是一些金属离子，随着晶粒尺寸的减小，氧空位缺陷的浓度增加，极化增强，纳米材料的这种表面状态对其介电性能有重要影响，使其静态介电常数远比常规材料的大。