Properties Of Barium Titanate Ceramics Research Articles

Understanding local physical properties of barium titanate ceramics depending on the synthesis conditions assisted by a machine learning algorithm

Barium titanate (BT) is widely used in electronic components, such as multilayer ceramic capacitors, owing to its high dielectric constant and piezoelectricity. The continuously increasing demand for more efficient devices has led to the development of smaller and more efficient BT ceramics by controlling the synthesis conditions. However, despite the decrease in size of BT grains to the nanoscale, the physical properties of BT ceramics have mostly been investigated on a macroscopic scale. In this study, we investigated the effects of synthesis conditions on local physical properties such as surface roughness, leakage current, and domain structure/switching using atomic force microscopy. We further applied machine learning analysis to effectively understand the effects of synthesis conditions on these physical properties; the analysis not only provides local information on BT ceramics but also a comprehensive understanding of their physical properties.

Effect of cerium substitution on structural and optical properties of barium titanate ceramics

Barium titanate shows interesting behavior with little modification in synthesis route and variation in doping concentration. Barium titanate being perovskite material belongs to ABO3 family, shows tetragonal structure. In this present work, BaTiO3 with varying doping concentration of CeO2 (2 wt%) was fabricated by solid state reaction method. Structural and morphological study reveals a change in crystallite size and grain growth. X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and a UV–VIS spectrophotometer were used to characterize the samples. Phases of the prepared samples were investigated by X-ray diffraction. The results of the investigation shows that pure barium titanate have no secondary phases. Pure form of barium titanate shows polycrystalline nature. Further, crystallite size, stress and strain for the doped sample were calculated using Scherrer method, Williamson-Hall analysis, Uniform deformation model (UDM), Uniform stress deformation model (USDM) and Uniform deformation energy density model (UDEDM) approaches. Crystallite size calculated by Scherrer method shows a variation with percentage doping. Doped sample shows reduce in crystallite size. Effect of size and strain induces X-ray peak broadening. In accordance with these findings, FE-SEM measurements demonstrate a shift in grain growth with Ce concentration with respect to pure barium titanate. X-ray diffraction results shows a good agreement with FE-SEM results. Peaks in the absorption are impacted by Ce ion doping concentration. An intriguing behavior of the ceramic is demonstrated by a considerable change in band gap with dopant. Cerium concentrations have a substantial impact on the physical and optical properties.

Effects of yttrium doping on structural, electrical and optical properties of barium titanate ceramics

In this report, we study the Yttrium-doped Barium Titanate (Y-BT) Ba1 − xYxTiO3 (with x = 0.00, 0.01, 0.03, 0.05, 0.07 mmol) perovskite ceramics synthesized by sol-gel method. The as-made powder samples were pressed into a pellet shape and subsequently sintered at 1300 °C for 5 h in air. The structural, morphological, electrical, and optical properties of the synthesized samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), impedance analyzer, and UV-Vis-NIR Spectroscopy respectively. The XRD study revealed the formations of single phase tetragonal structure of Barium Titanate (BT) with ∼23–33 nm mean crystallite size. The crystallite size increases initially with Y-doping, found at about 33 nm for x = 0.01, and reduces for increase in Y3+ concentration further. The microstructural study from FESEM depicts the uniform distribution of compact and well-faceted grain growth for Y-BT in contrast with undoped barium titanate. The average grain size (∼0.29–0.78 μm) of the Y-BT decreases with increasing doping concentration. Frequency-dependent impedance analyses show enhanced dielectric properties like dielectric constant, quality factor, and conductivity with low dielectric loss in the presence of Yttrium. The optical bandgap energy (∼2.63–3.72 eV) estimated from UV-Vis-NIR diffuse reflection data shows an increasing trend with a higher concentration of yttrium doping.

Effect of nickel and zinc co-substitution on the structural and dielectric properties of barium titanate ceramics

Effect of nickel and zinc co-substitution on the structural and dielectric properties of barium titanate ceramics

Effects of Yttrium Doping on Structural, Electrical and Optical Properties of Barium Titanate Ceramics

Effects of Yttrium Doping on Structural, Electrical and Optical Properties of Barium Titanate Ceramics

Dependence of the dielectric properties of barium titanate ceramics and a composite based on it on the sintering temperature

In this paper, we compare the structure and dielectric properties of the samples of barium titanate ceramics that have been sintered at temperatures of 1100, 1150, 1200, 1250 and 1350 °C and dielectric characteristics of the samples of barium titanate (80 vol.%) — barium ferrite (20 vol.%). It is shown that only samples sintered at the temperature of 1250 and 1350 °C have polarization sufficient for the existence of the piezoelectric effect. For the same samples, the pyroelectric coefficient and reversal polarization significantly exceed those for samples sintered at lower temperatures. Analysis of the samples structure confirmed the dependence of the dielectric properties of the barium titanate ceramics on the grain size and, as a consequence, on the sintering temperature. Based on the studies carried out, the optimal temperature (1250 °С) for obtaining composite samples of barium titanate (80 vol.%) — barium ferrite (20 vol.%) was selected. The temperature dependence of the dielectric constant for the composite samples based on barium ferrite — barium titanate with a sintering temperature of 1250 °C is similar to the dependence for the BaTiO3 ceramic samples sintered at 1350 °C. At room temperatures, the permittivity of the composite samples is also significantly higher than that of the barium titanate ceramic samples obtained at the same sintering temperatures. The addition of barium ferrite to the barium titanate not only increased the permittivity of the composite, but also led to a diffusing of the ferroelectric phase transition and a shift in the temperature of the maximum of the dielectric constant by 10 degrees towards high temperatures.

Examination of the Influence of Cobalt Substitution on the Properties of Barium Titanate Ceramics

Examination of the Influence of Cobalt Substitution on the Properties of Barium Titanate Ceramics

Effect of sintering temperature on dielectric properties of barium titanate ceramics and composite

The structure and dielectric properties of barium titanate ceramics samples sintered at 1100, 1150, 1200, 1250 and 1350 °C have been compared with the dielectric properties of 80 vol.% barium titanate + 20 vol.% barium ferrite composite samples sintered at 1150, 1200 and 1250 °C. It has been shown that polarization sufficient for existence of the piezoelectric effect is only achieved in barium titanate samples sintered at 1250 and 1350 °C. Furthermore the pyroelectric coefficient and reversal polarization of these samples are far higher than those of samples sintered at lower temperatures. Analysis of the sample structures has confirmed that the dielectric properties of barium titanate ceramics depend on grain size and therefore on sintering temperature. Based on the experimental results we have selected the optimum sintering temperature for 80 vol.% barium titanate + 20 vol.% barium ferrite composite to be 1250 °С. Further increase in sintering temperature to 1300 °C showed that this composite has a eutectic. The temperature dependence of the permittivity of the barium titanate / barium ferrite composite sintered at 1250 °С is similar to that of BaTiO3 ceramics samples sintered at 1350 °С. The room temperature permittivity of the composite samples also proves to be far higher than that of barium titanate ceramics samples sintered at the same temperatures. Barium ferrite addition to barium titanate increases the permittivity of the composite and also diffuses the ferroelectric phase transition and shifts the permittivity maximum temperature by 10 °C towards higher temperatures.

Effect of Nickel and Cobalt co-substitution on the structural and dielectric properties of Barium Titanate ceramics

The influence of Nickel and Cobalt co-substitution on the structure and dielectric properties of barium titanate (BaTiO3) ceramics has been investigated. Nickel and Cobalt co-substituted BaTiO3 ceramics with general formula BaTi1−x(Ni,Co)xO3 has been synthesized for x = 0.0, 0.02, 0.04 and 0.08 through conventional solid state reaction route. The structural analysis carried out by X-ray diffraction reveals the successful incorporation of Ni2+ and Co2+ ions in the Ti4+ site of BaTiO3 with all samples under study having tetragonal structure. However the tetragonality (c/a ratio) seems to be decreasing with increase of co-substitution. The dielectric measurements are done at different frequencies and temperatures. The room temperature dielectric constant decreased considerably for the Ni and Co co-substituted samples. The phase transition of the BaTi1−x(Ni,Co)xO3 has been investigated by studying the temperature dependence of dielectric constant. Nickel and Cobalt co-substituted samples showed diffused nature of phase transition with a notable reduction in the Curie temperature with the increase of co-substitution. The Curie temperature is reduced to 104 °C for x = 0.08 composition whereas for x = 0.0 the Curie temperature is 123 °C. Enhancement in conductivity is observed with addition of Nickel and Cobalt addition. Nearest-neighbour hopping model is used to explain the conduction in the samples under study and energy of activation for conduction is calculated from Arrhenius plot.

Influence of surface coating on the microstructures and dielectric properties of BaTiO3 ceramic via a cold sintering process.

We present herein a modified cold sintering process (CSP) for BaTiO3 ceramics using a surface coating at the particle surface which could enhance the relative density of BaTiO3 up to ∼93.5% at 220 °C and 500 MPa. The surface coating greatly enhances the ceramic density, mainly because it facilitates the dissolution–precipitation process during CSP. Ba vacancies form at the surface of the coated powders, so Ba(OH)2 solution is used to compensate Ba ions in the as-cold-sintered ceramics, which increases the dielectric permittivity. Post-annealing at 700 and 900 °C increases the relative density to 97%, and the resulting relative dielectric permittivities are 810 and 1550, respectively, at room temperature and 1 kHz. This technique may also be extended to materials with very small, incongruent solubility in water or volatile solutions that use the cold sintering process.

Mono and co-substitution of Sr2+ and Ca2+ on the structural, electrical and optical properties of barium titanate ceramics

In this work, Ba0.9Sr0.1TiO3, Ba0.7Sr0.3TiO3, Ba0.5Sr0.5TiO3, Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 have been synthesized to evaluate the influence of mono and co-substitution of A-site dopants (Sr2+ and Ca2+) on the structural, electrical and optical properties of BaTiO3 ceramics. Sr2+ added samples showed a tetragonal structure which became slightly distorted with increasing Sr2+ concentration and finally achieved a cubic structure for x = 0.50. Ba0.5Ca0.5TiO3 also retained their tetragonality with limited solubility. Presence of second phase, CaTiO3 demonstrated the fact of restricted solubility. The concurrent effect of Sr2+ and Ca2+ didn't alter the tetragonal structure. Sr2+ substitution enhanced the apparent density as well as grain size which stimulated the domain wall motion and improved dielectric properties. However, the ferroelectric nature of Ba1-xSrxTiO3 was poor due to the redistribution of point defect at grain boundary. The optical band gap was found to be reduced from 3.48 eV to 3.28 eV with increasing Sr2+ content. Co-substitution of cations improved the electrical property significantly. The highest value of dielectric constant was found to be ∼547 for Ba0.5Ca0.25Sr0.25TiO3 ceramics. Both Ba0.5Ca0.25Sr0.25TiO3 and Ba0.5Ca0.5TiO3 had developed P-E loop having lower coercive field and moderate optical band gap energy. Co-doping with Sr2+ and Ca2+ was a good approach enhancing materials electrical as well as optical property.

Properties of barium titanate ceramics based on powder synthesized in supercritical water

Fine-crystalline barium titanate was synthesized by a new method using supercritical water and examined as a raw material for dielectric ceramics preparation by semidry pressing and further high-temperature sintering. The nature of temporary technological binder utilized at the stage of pressing significantly affected the structural, mechanical and electro-physical properties of BaTiO3 ceramics. Ceramics prepared from BaTiO3 powder synthesized in supercritical water possessed necessary applied characteristics: the dielectric permittivity as high as 2819 and loss tangent as low as 0.012.

Characterization of mechanical properties of barium titanate ceramics with different grain sizes

AbstractIn this paper, three BaTiO3 powders of various particle size distributions were obtained as a result of mechanical activation in the mixer mill. Green barium titanate pellets and cylindrical specimens were fabricated by both uniaxial and isostatic pressing methods. As a result of the application of different maximal sintering temperatures, the obtained materials were characterized by various average grain sizes: 0.8 μm, 20 μm and 31.0 μm. The basic properties of sintered pellets and cylinders were determined and the influence of materials average grain size on their Young’s modulus and compressive strength were determined through compression tests in a uniaxial testing machine, Zwick/Roell Z100. The elastic properties were similar for tested materials with a different grain size. However, the microstructure of BaTiO3 strongly influenced the compressive strength.

Structural and dielectric properties of Zr doped BaTiO3 synthesized by microwave assisted chemical route

Lead-free ferroelectric nano ceramics of BaZrxTi1-xO3 (x=0.1, 0.2 and 0.3) were prepared by means of microwave assisted chemical route. The structural, dielectric and electrical properties were examined. The crystalline structure of the specimens was studied by X-ray diffraction patterns. All the samples showed pure single phase of perovskite structure with space group of I4/mcm. X-ray diffraction data illustrated that there is no secondary phases exist. Structural and electrical properties of barium titanate ceramics are influenced significantly by small additions of Zr. The electrical conductivity showed higher values at x=0.2 and decreased at higher Zr content. The Hall charge mobility is found to decrease with Zr addition. The negative sign of the Hall coefficient RH confirms the dominant n-type conduction in all samples. The charge carrier concentration decreased with Zr content increase. Suggested potential application for this ceramics compound is in high storage multilayer capacitors and ferroelectric applications.

Dielectric spectroscopy analysis of BaTiO3 with mechanochemical process in different liquids

Distilled water, methanol, and acetone, have been used to investigate the effects of the homogenization medium on the impedance properties of BaTiO3 ceramics produced by the solid state reaction method. The complex permittivity, complex impedance, resistivity, and complex electric modulus of the ceramics were studied by the dielectric spectrometer in a wide frequency range of 100μHz to 20MHz at room temperature. The complex impedance and complex electric modulus showed that the materials have a relaxation time with a different mean time constant called the Maxwell-Wagner-Sillars (MWS) type relaxation. The minimum dielectric loss found the ceramic reagents homogenized in distilled water, which is crucial for many electronic applications. The complex permittivity and resistivity measurements showed that using water instead of acetone and methanol has a positive effect on the small loss of electrical properties of barium titanate ceramics.

Ferromagnetic properties of barium titanate ceramics doped with cobalt, iron, and nickel

The influence of annealing in strongly reducing atmosphere on the magnetic properties of hexagonal BaTiO3 + 0.04 BaO + x/2 Co2O3 (0.0025 ≤ x ≤ 0.10) ceramics was investigated. The samples air-sintered at 1673 K were subsequently tempered at 1473 K in H2/Ar stream. While the as-sintered samples exclusively exhibit paramagnetic behavior, the annealed samples show distinct saturation in the field dependence of the magnetization at 300 K measured in the range between −90 and 90 kOe. Besides, the field dependence of the magnetization is hysteretic with coercive fields in the order of 100 Oe. Both properties point to ferromagnetic regions which were identified as precipitations of metallic cobalt by TEM and EDX. The cobalt precipitations were exclusively found in tetragonal grains which were completely Co-free outside the precipitations. Obviously, these tetragonal grains were formed during the annealing process when the Co content of the formerly hexagonal grains was concentrated into metallic Co particles by diffusion processes. Hence, the Co-free matrix of the grains transformed into the cubic phase which is the equilibrium phase of undoped BaTiO3 at the annealing temperature 1473 K and during cooling to room temperature into tetragonal phase. The size of the metallic precipitations ranges from about 20 to 100 nm. A reduction both of the annealing temperature to 1373 K and of the annealing time from 120 to 30 min did not change the minimum particle size, but now, the very rare precipitations only occurred at triple points or grain boundaries. EPR measurements confirmed the occurrence of the ferromagnetic precipitations. While at 300 K, the as-sintered samples did not show any Co EPR signal, the annealing in strongly reducing atmosphere caused a strong and broad line which is attributed to the ferromagnetic resonance signal of the Co precipitations. The investigations were extended for the dopants, iron or nickel, with a nominal sample composition of BaTiO3 + 0.04 BaO + 0.01 Fe2O3 or 0.02 NiO, respectively. The field dependence of the magnetization as well as the EPR spectra showed similar results compared to the case of Co-doped samples. Hence, also in Fe- or Ni-doped BaTiO3 ceramics, ferromagnetic properties are caused by annealing in strongly reducing atmosphere.

Effect of Semiconductor Element Substitution on the Electric Properties of Barium Titanate Ceramics

Abstract The investigated ceramics were prepared by a solid-state reaction from simple oxides and carbonates with the use of a mixed oxide method (MOM). The morphology of BaTi0.96Si0.04O3 (BTSi04) ceramics was characterised by means of a scanning electron microscopy (SEM). It was found that Si+4 ion substitution supported the grain growth process in BT-based ceramics. The EDS results confirmed the high purity and expected quantitative composition of the synthesized material. The dielectric properties of the ceramics were also determined within the temperature range (ΔT=130-500K). It was found that the substitution of Si+4 ions had a significant influence on temperature behavior of the real (ε’) and imaginary (ε”) parts of electric permittivity as well as the temperature dependence of a.c. conductivity. Temperature regions of PTCR effect (positive temperature coefficient of resistivity) were determined for BTSi04 ceramics in the vicinity of structural phase transitions typical for barium titanate. No distinct maximum indicating a low-temperature structural transition to a rhombohedral phase in BTSi04 was found. The activation energy of conductivity was determined from the Arrhenius plots. It was found that substitution of Si ions in amount of 4wt.% caused almost 50% decrease in an activation energy value.

Electrical and Mechanical Properties of Alumina Mixed BaTiO3 Ceramics Incorporating Nano-sized Powders

Barium titanate and alumina mixed (from 0.5 to 5 vol.%) barium titanate composite ceramics incorporating nano-sized powders were prepared by the conventional electroceramic process. With the increase of alumina addition content, the densities of the ceramics gradually decreased from 5.67 g/cm3 to 5.3 g/cm3, the hardness was enhanced, and the phase transition from tetragonal to cubic became disperse. Comparable dielectric and piezoelectric properties of barium titanate ceramics could be obtained when the alumina addition content was no more than 1 vol.%.

Effect of Fe3+ substitution on structural, optical and magnetic properties of barium titanate ceramics

Multiferroic BaTi1−xFexO3 (0≤x≤0.12) materials were synthesized using the solid-state reaction method. The influence of Fe on the crystalline structure, the electronic structure, the optical properties and the magnetic property of BaTi1−xFexO3 samples were investigated. The obtained X-ray diffraction patterns, Raman and UV–vis spectra showed that the structure of the material sensitively depends on Fe dopant content, x, and transforms gradually from the tetragonal (P4mm) phase to the hexagonal (P63/mmc) one with increasing x. The photoluminescence emission of BaTi1−xFexO3 was attributed to structural disorder. All of the samples exhibit both ferroelectricity and ferromagnetism at room temperature. The relaxor like behavior was observed for all samples. The magnetization at a magnetic field of 1T abnormally depends on x, increases up to 0.1 then decreases monotonously afterward. This anomaly in the magnetic behavior can be explained in terms of the changes in the oxidation state of ions such as the Fe3+-to-Fe4+ and/or Ti4+-to-Ti3+ change induced by oxygen vacancies. The substitution of Fe into Ti sites also causes the changes in the conductivity of the material and impurity (acceptor) levels in the band gap, which can be evident from the absorption spectra, and time-dependent leakage current measured at room temperature.

Effects of La Doping on the Structural and Dielectric Properties of Barium Titanate Ceramics

Polycrystalline samples of Ba1-xLaxTiO3 (x = 0.0, 0.002, 0.004) were prepared by a standard high-temperature solid-state reaction method. XRD studies confirmed the formation of a polycrystalline compound with a tetragonal crystal structure. SEM images suggested the presence of a polycrystalline microstructure with certain degree of porosity, and the grains appeared to be distributed inhomogeneously throughout the pallet samples. Dielectric studies indicated a ferroelectric–paraelectric phase transition with a clear shift in the Curie temperature (Tc) of BaTiO3 towards a lower temperature upon doping. The brick-layer model was used to study the potential barrier and the structure of the grain-boundary region of the Ba9.998La0.002TiO3 and Ba9.996La0.004TiO3 ceramics. These ceramics exhibited good density and a homogeneous distribution of the grains. The thickness of the grain-boundary region was calculated to be approximately 200 nm.