Dielectric Properties Of BaTiO3 Ceramics Research Articles

Effects of Strontium on the Structural, Optical, and Microwave Dielectric Properties of Ba2Ti9O20 Ceramics Synthesized by a Mixed Oxide Route.

Solid solutions of Sr-doped barium nonatitanate (Ba2Ti9O20) ceramics were synthesized by a mixed oxide route, studied their structural, microstructural, optical, and microwave dielectric properties were studied. X-ray diffraction (XRD) has been used to reveal the structure and crystallite size of doped Ba2Ti9O20 ceramics. Rietveld refinements of XRD patterns revealed that all of the ceramics have a tetragonal structure with space group I4/m. The surface morphologies of all the samples were characterized by using scanning electron microscopy (SEM). Fourier transform infrared (FT-IR) studies gave the O–H and Ti–O modes of vibrations. The stretching modes of Ti–O and O–H were noted at 1400, 2960, 3700, and near to 440 cm–1, respectively. The band gap energy decreases with increasing Sr2+ contents, and a high value (2.12 eV) was observed in the base sample. The microwave dielectric properties of the ceramic samples were studied at different frequencies ranging from 1 to 2 GHz by using impedance spectroscopy. The obtained results showed the suitability of these samples for microwave dielectric resonator (antenna) applications.

The influence of the distribution of Cu-rich phase on the micromorphology and dielectric properties of BaTiO3 ceramics

The influence of the distribution of Cu-rich phase on the micromorphology and dielectric properties of BaTiO3 ceramics

Improvement of microwave dielectric properties of Ba2Ti9O20 ceramics using [Zn1/3Nb2/3]4+ substitution for Ti4+

Ba2[Zn1/3Nb2/3]xTi9−xO20 (x = 0–0.5) ceramics with high-quality factors were successfully prepared via traditional solid-state method. In this work, the microstructure and microwave dielectric properties of the samples were studied. The X-ray diffraction patterns indicated that two different phases BaTi4O9 and Ba2Ti9O20 existed at x = 0, while the phase of Ba2Ti9O20 was found gradually dominating in specimens with the doping of [Zn1/3Nb2/3]4+. At the level of x = 0.5, a fraction of the monoclinic phases of Ba2Ti9O20 were transformed into the triclinic phase. Furthermore, the SEM and relative density were used to confirm the homogeneous microstructure of the Ba2[Zn1/3Nb2/3]xTi9−xO20 ceramics. The doping of [Zn1/3Nb2/3]4+ can effectively improve the microwave properties of Ba2Ti9O20 ceramics, which are shown as the increase of dielectric constant, quality factor, and the stability of temperature coefficient. Particularly, the excellent microwave dielectric properties were achieved for the Ba2[Zn1/3Nb2/3]0.3Ti8.7O20 ceramics sintered at 1300 °C, with er ~ 39.3, a high Q × f ~ 43,879 at 6 GHz, and a τf ~ + 7 ppm/°C.

Niobium doping effect on BaTiO3 structure and dielectric properties

The effect of Nb on the microstructure and dielectric properties of BaTiO3 ceramics was investigated. The Nb/Mn–BaTiO3 ceramics were prepared using a conventional solid-state method. The concentration of Nb varied from 0.1 to 5.0 at% but Mn was fixed at 0.05 at%.The SEM indicated that compositions of 0.1 and 0.5 at% Nb displayed a fairly uniform microstructure and homogeneous distribution of additives, with a grain size of less than 2 μm. In highly doped samples a wide range of microstructural features was observed, from homogeneous and completely fine-grained microstructure to the appearance of secondary abnormal grains with core-shell structure.The dielectric constant and the loss tangent of modified ceramics were measured as a function of temperature (20–180 °C) and frequency (100 Hz-1MHz) for different concentrations of additives. The obtained results have shown that the dielectric constant at, both, room temperature (εr) and Curie temperature (εrmax), decreased as the concentration of Nb5+ increased. Thus, the highest values for the dielectric constant at room temperature (εr = 6648) as well as at Curie temperature (εrmax = 7680) were measured for the 0.1Nb/Mn–BaTiO3 samples sintered at 1350 °C.The highly doped BaTiO3 ceramics were found to exhibit lower values of the dielectric constant and low dielectric losses at room temperature. In these samples, stable dielectric permittivity with a flat dielectric behavior over a wide temperature range is observed.The Curie constant for all series of samples decreases with an increase of dopant concentration and the highest values were measured from samples doped with 0.1 at% Nb. The effect of additives on the Curie constant change is more pronounced at higher sintering temperatures. The analysis of the critical nonlinearity exponent (γ = 1.07–1.27), for lower dopant concentrations, shows a sharp phase transformation. For samples with increased Nb content, the degree of nonlinearity γ is higher indicating a diffuse phase transformation.

Effect of SiO2 on dielectric properties of core-shell Sr and Tm co-doped BaTiO3@SiO2 ceramics

Sr and Tm co-doped Ba0.7Sr0.3Ti0.9925Tm0.01O3 (BST) and core-shell structured BST@SiO2 ceramics were prepared by sol-gel method and conventional sintering. Along with the obvious perovskite phases in the BST and BST@SiO2 powders, a new phase, Ba2TiSi2O8, was confirmed in the sintered BST@SiO2 bulk by XRD analysis. TEM analysis revealed that the BST powders were coated with an amorphous SiO2 film, while SEM analysis indicated that the SiO2 film plays a role in grain size reduction. The dielectric losses of BST@SiO2 ceramics reduced effectively compared to that of BST. In addition, the Curie peak of the BST@1%SiO2 ceramic significantly broadened and the Curie temperature shifted toward lower temperatures; this provides a new approach to improving the dielectric properties of BaTiO3 ceramics.

Effect of co-substitution of Sm3+ and Fe3+ ions on structural and dielectric properties of BaTiO3 ceramics

The material series of polycrystalline ferroelectric ceramics with compositional formula (Ba1-xSmx)(Ti1-xFex)O3 (with 0 ≥ x ≥ 0.01 in steps of 0.0025) was prepared by solid-state reaction method. The samples were sintered at 1300 °C (for x = 0) and 1325 °C for (x > 0). The sintered samples were subjected to X-ray diffraction (XRD) analysis and found to have single phase with tetragonal perovskite structure. Average grain size decreases with increase in substituent content. Dielectric behavior was studied as a function of temperature at different frequencies (1, 10,100,1000 kHz). The lattice constant ‘c’, tetragonality‘c/a ratio’ and Curie temperature ‘Tc’ was found to decrease with increase in the substituent content whereas the room temperature dielectric constant increases with substituent content. Large value of temperature coefficient of capacitance ‘Tcc’> 10%/°C near Tc was observed for all the samples.

Effect of BiMO3 (M=Al, In, Y, Sm, Nd, and La) doping on the dielectric properties of BaTiO3 ceramics

Abstract In this study, in order to enhance the energy storage density, 10% BiMO 3 doping is performed in BaTiO 3 ceramics (M=Al, In, Y, Sm, Nd, La) by a traditional solid-state method. The effects of different M 3+ radii on the structural characteristics, dielectric properties, and energy storage are investigated systematically. The locations of the M-ions gradually shift from B-site substitutions to A-site substitutions with the increase in the ionic radius, which affect the structural characteristics and the dielectric properties. When 80 M3+ m ) and remnant polarization (P r ), 0.9BaTiO 3 –0.1BiInO 3 exhibits the maximum energy density of 0.753 J/cm 3 and the highest energy efficiency of 89.4%, which exhibits slim P-E hysteresis loops for energy storage applications.

Fabrication of lanthanum doped BaTiO3 fine-grained ceramics with a high dielectric constant and temperature-stable dielectric properties using hydro-phase method at atmospheric pressure

Lanthanum doped BaTiO3 powders were synthesized by the hydro-phase method at atmospheric pressure, which controls the uniformity and particle size of the ceramic powders. The effects of La3+ ions concentration on the microstructure and dielectric properties of BaTiO3 ceramics were studied. The results suggested that both the average grain size and dielectric constants (εr and εmax) of the ceramics decreased as the concentration of La3+ increased. The ceramic met the X8R specifications: La3+ ions concentration of 3mol%, a permittivity of 2322, low dielectric loss of less than 0.6% at room temperature, and average grain size of about 260nm.

Effects of ultrasonication and conventional mechanical homogenization processes on the structures and dielectric properties of BaTiO3 ceramics

The effects of the homogenization process on the structures and dielectric properties of pure and Nb-doped BaTiO3 ceramics have been investigated using an ultrasonic homogenization and conventional mechanical methods. The reagents were homogenized using an ultrasonic processor with high-intensity ultrasonic waves and using a compact mixer-shaker. The components and crystal types of the powders were determined by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The complex permittivity (ε′, ε″) and AC conductivity (σ′) of the samples were analyzed in a wide frequency range of 20Hz to 2MHz at room temperature. The structures and dielectric properties of pure and Nb-doped BaTiO3 ceramics strongly depend on the homogenization process in a solid-state reaction method. Using an ultrasonic processor with high-intensity ultrasonic waves based on acoustic cavitation phenomena can make a significant improvement in producing high-purity BaTiO3 ceramics without carbonate impurities with a small dielectric loss.

Dielectric Properties of BaTiO3 Ceramics Doped with Al3+ and Nb5+

Al3+ and Nb5+ doped on the B-sites of BaTiO3 ceramics were prepared by solid state reaction and the dielectric properties of ceramics were investigated. Dielectric constant peak shifted to the low temperature and broadened pronouncedly by Al3+ addition. The second phase appeared as x > 0.04. Furthermore, the dielectric properties of Nb5+ doped in the BaAl0.04Ti0.96O3 ceramics were discussed. As Nb5+ increased, the maximum dielectric peak shifted to low temperature. Meanwhile, the defect energy of BaTiO3 doped with Al3+ and Nb5+ was calculated by atomic simulation and the effect of defects on the dielectric properties of ceramics was discussed.

Low‐Temperature Synthesis and Thermodynamic and Electrical Properties of Barium Titanate Nanorods

Studies regarding the morphology dependence of the perovskite‐type oxides functional materials properties are of recent interest. With this aim, nanorods (NRs) and nanocubes (NCs) of barium titanate (BaTiO3) have been successfully synthesized via a hydrothermal route at temperature as low as 408 K, employing barium acetate, titanium isopropoxide, and sodium hydroxide as reagents without any surfactant or template. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray powder diffraction (XRD), used for the morphology and structure analyses, showed that the NRs were formed by an oriented attachment of the NCs building‐blocks with 20 nm average crystallites size. The thermodynamic properties represented by the relative partial molar free energies, enthalpies, and entropies of the oxygen dissolution in the perovskite phase, as well as the equilibrium partial pressure of oxygen, indicated that NRs powders have lower oxygen vacancies concentration than the NCs. This NRs characteristic, together with higher tetragonallity of the structure, leads to the enhancement of the dielectric properties of BaTiO3 ceramics. The results presented in this work show indubitably the importance of the nanopowders morphology on the material properties.

Microstructure and Dielectric Properties of Rare-Earth Doped BaTiO3 Ceramics

The specimens of BaTiO3 doped with 0.01, 0.1 and 0.5 wt% of Er2O3 or Ho2O3 used for this investigation were prepared by the conventional solid state reaction. The specimens were sintered at 1350°C in an air atmosphere for 4 hours.The grain size and microstructure characteristics for various samples and their phase composition was carried out using a scanning electron microscope SEM equipped with EDS system. SEM analysis of Er/BaTiO3 and Ho/BaTiO3 doped ceramics showed that in samples doped with a low level of rare-earth ions, the grain size ranged from 10–60μm, while with the higher dopant concentration the abnormal grain growth is inhibited and the grain size ranged between 2–10μm.We also applied the fractal method in microstructure analysis of sintered ceramics especially as influence on dielectric properties of BaTiO3 ceramics. These fractal effects have been used for better understanding of intergranular capacitors.

Dimension effects on the dielectric properties of fine BaTiO3 ceramics

It is found that the core-shell structured grains are easy to produce for fine grain doped BaTiO3 ceramics in the sintering process. We study the influence of the core-shell structure on the Curie—Weiss temperature and dielectric properties of BaTiO3 ceramics by using effective medium approximation (EMA). Considering the second approximation, the dielectric properties of fine grain doped BaTiO3 ceramics are consistent with experimental data.

Low temperature sintering of high permittivity BaTiO3 based X8R ceramics doped with Li2O–Bi2O3–B2O3 frit

BaTiO3 ceramics doped with 3wt% K0.5Na0.5NbO3 content and different Li2O–Bi2O3–B2O3 frit as the sintering aids were prepared by the conventional solid state ceramic route. The effects of the Li2O–Bi2O3–B2O3 frit on the phase composition, microstructure and dielectric properties of BaTiO3 ceramics were investigated. Results show that the BaTiO3 pellet has pure tetragonal crystal structure. And the dielectric ceramic with high permittivity of 5585 and excellent densification were obtained at a sintering temperature of 980°C, meeting X8R specifications. The results also suggest that the developed BaTiO3 based X8R ceramics may serve as a promising candidate for fabricating cheap multilayer capacitors with base metal as inner electrode.

Processing and Characterizations of Bi<sub>2</sub>O<sub>3</sub>/BaTiO<sub>3</sub> Ceramic

The objective of this work is to provide the process for making BaTiO3-based ceramics by adding bismuth oxide (Bi2O3) into the system. The attention is also focused on synthesis conditions, where sintering temperature exhibits a pronounced effect on phase formation, density, microstructure and dielectric properties of BaTiO3 ceramics doped with different contents of Bi2O3 nanoparticles. The phases of BaTiO3-based ceramics have been prepared by solid state reaction using different Bi2O3 amount and characterized by X-ray diffractometry, Archimedes’s method, scanning electron microscopy and dielectric spectroscopy. The results show that single phase of BaTiO3 with no evidence of secondary phase forms in all samples. Abnormal grain growth was found in pure BaTiO3 ceramic with 37.30 µm of average grain size. After added Bi2O3 nanoparticles into system, the grain size significantly decreases and the sintering temperature of BaTiO3-based ceramics efficiently reduces without degrading the dielectric characteristics.

Effects of BaNb2O6 addition on microstructure and dielectric properties of BaTiO3 ceramics

(1 − x)BaTiO3–xBaNb2O6 [(1 − x)BT–xBN] ceramics with x = 0, 0.005, 0.008, 0.01, 0.02, 0.03 were prepared by a conventional solid-state reaction route. The effect of BN addition on phase composition, microstructure and dielectric properties of BT-based ceramics were investigated by X-ray diffraction, scanning electron microscope and impedance spectroscopy. The results showed that a systematic structure change from the ferroelectric tetragonal phase to pseudo-cubic phase was observed near x = 0.01 at room temperature. It resulted in a considerable change of density, grain size and dielectric properties of the samples when BN was introduced. Meanwhile, it also lowered the sintering temperature of the ceramics. The dielectric constant peak and the variation rate of capacitance at Curie temperature are markedly depressed and broaden with increasing BN content. Especially, the ceramics with x = 0.008 and x = 0.01 showed good dielectric properties over the measured temperature range. Optimal dielectric properties of e = 3,851, tanδ = 0.7 % at room temperature and Δe/e25 ≤ ±6.8 % (−55 to 125 °C) were obtained for the BT-based ceramics doped with 0.8 mol% BN, which was obviously superior to BaTiO3 and BaNb2O6 ceramic, and it met the requirements of EIA X7R specifications.

Dielectric investigations in nanostructured tetragonal BaTiO3 ceramics

In this paper, structural and dielectric properties of BaTiO3 ceramics obtained under extreme conditions were investigated. The temperature dependent dielectric investigations revealed that the phase transition temperatures of the BaTiO3 ceramics were raised as a function of residual strains associated to the nanostructuration, while structural characterizations showed a tetragonal arrangement at room temperature. From the frequency dependence analyses of the imaginary parts of dielectric permittivity, impedance and modulus function, three relaxation processes were identified. Two of them exhibit activation energies of 0.45 and 0.63eV, and were attributed to single and double-ionization of oxygen vacancies. The whole set of results also indicated that the electrons resulting from the ionization of oxygen vacancies are trapped and do not contribute to the electrical conductivity, while the physical properties of the analyzed samples were enhanced by retaining a strained microstructure.

Effects of K0.5Bi0.5TiO3 addition on dielectric properties of BaTiO3 ceramics

(1−x)BaTiO3–xK0.5Bi0.5TiO3 (abbreviated as BT–KBT, 0.10≦x≦0.15) dielectric ceramics were prepared by a conventional oxide mixing method. The effects of KBT content on the densification, microstructure and dielectric properties of BT ceramics were investigated. The density characterization results show that the addition of KBT significantly lowered the sintering temperature of BT ceramics to about 1280 °C. The XRD results showed that the phase compositions of all samples were pure tetragonal phases. The dielectric constant and dielectric loss firstly increased and then decreased with the increase of KBT. In addition, dielectric constant and dielectric loss versus frequency were characterized in the frequency range from 100 Hz to 2 MHz. It is found that the dielectric constant and the dielectric loss changed with the increase of KBT contents regularly.

Grain Size‐Dependent Properties of Dense Nanocrystalline Barium Titanate Ceramics

The grain size influence on the dielectric relaxation and nonlinear dielectric properties of BaTiO3 ceramics with grain size in the range of (92÷936) nm densified by Spark Plasma Sintering (SPS) from ultrafine powders were investigated. The progressive reduction of the Curie temperature and of the effective permittivity results from a combination of intrinsic size effects and low‐permittivity grain boundary layer. A model of dielectric cylindrical cavities was employed in order to calculate intrinsic effective permittivity values in GHz range. An interesting feature is the presence of a thermally activated Debye‐like relaxation in the ferroelectric state of ceramics with grain size above 300 nm, with activation energies of 0.45–0.49 eV, which seems to be related to the domain walls forced motion under the applied field. By diminishing grain size, a progressive reduction of the ferroelectric nonlinear character was obtained, reaching a macroscopic non‐switching character and a linear permittivity versus field dependence for the finest ceramics (grain size of 90–100 nm) until very high values of the applied field. The observed behavior supports the idea of frozen polarization induced by pinning centers as due to a large number of grain boundaries and charged defects in the fine structures.

Processing parameter influence on BaTiO3 ceramic fractal microstructure and dielectric characteristics

In the process of BaTiO3 ceramics consolidation, technological parameters like sintering temperature, pressing pressure and additives significantly determine the microstructure and electrical properties. Slight change of a particular sintering parameter can considerably change the microstructure as well as the electrical parameters. Structural complex grain–contact–grain is observed on Ho doped BaTiO3 ceramics, sintered from 1320 to 1380°C. The new configuration model of ceramic grain contact surfaces is presented in this paper. This model is based on Coble’s two-sphere approximation and its generalisation to ellipsoidal geometry. The integral contact surface directly influences the value of the total ceramic capacity. Fractal method is applied for intergrain contact analysis. Ceramic grains are considered to have fractal surface (as it is elsewhere in nature) and, therefore, fractal structure influences on the dielectric properties of BaTiO3 ceramics. The obtained results give better understanding of ceramic microstructure with the final aim to establish significant interrelation among processing, structural and electrical parameters.