Properties Of BaTiO3 Research Articles

Phase structure and dielectric properties of doped BaTiO3 ceramics

The effects of two rare earth oxides such as CeO2 and Sm2O3 on the phase structure and dielectric properties of BaTiO3 ceramic were investigated. Results indicate that the dielectric constant of this system will increase greatly with the increasing content of these two oxides, and Ce(superscript 4+) substitutes for Ba(superscript 2+) located at A-site in ABO3 structure Quantitative XRD analysis shows that c/a ratio in the sample with addition of CeO2 will increase, which implies the increase of tetragonality in system, causing the augment of dielectric constant, and the decrease of the crystal’s geometrical symmetry results in curie-temperature moving towards low temperature; Sm(superscript 3+) (0.096 nm) substitutes for Ba(superscript 2+) (0.135 nm) possessing larger radius in A-site and the electrovalency in A-site increases, the mutual effect is strengthened, so the polarization is enhanced, and the dielectric constant increases notablely.

Particle Size and Temperature Dependence of THz-Region Dielectric Properties for BaTiO3 Nanoparticles

Impurity-free, defect-free and dense barium titanate (BaTiO 3 ) nanoparticles with various particle sizes from 22 to 500 nm were prepared using a 2-step thermal decomposition method. Powder dielectric measurement clarified that dielectric constant of BaTiO 3 particles with 58 nm exhibited a maximum around 15,000 at 20.00°C. To explain this high dielectric constant, THz-region dielectric properties of BaTiO 3 nanoparticles, especially Slater transverse optic (TO) mode frequency, were estimated using the far infrared (FIR) reflection method. As the result, it was found that the Slater TO mode of BaTiO 3 particles with 58 nm exhibited a minimum.

Sintering time dependence on PTC properties in BaTiO3-(Bi1/2Na1/2)TiO3 ceramics

Sintering time dependence on PTC properties in BaTiO3-(Bi1/2Na1/2)TiO3 ceramics

Simultaneous Measurements of Thermal, Electrical, and Acoustic Properties of BaTiO3 – New Feature of 403 K Phase Transition

In order to obtain useful information on the transient process of phase transitions in ferroelectrics by various methods including calorimetry, the “mK-stabilized cell” of a small size has been developed. It is based on the heat flux differential scanning calorimeter (DSC) and has a temperature stability better than 1 mK. The “cell” can be used to change the temperature under nearly quasi-static conditions by an infinitesimally small rate not only on heating but also on cooling while passing through the transition points. It enables simultaneous measurements of endothermic heat and exothermic heat along with dielectric constants, displacement currents, etc. with a high degree of temperature resolution. X-ray diffraction measurements for sensing thermal anomalies are also possible by a minor modification of the “cell.” Precise and simultaneous measurements of thermal, electrical, and acoustic properties were carried out at the 403 K phase transition in BaTiO3 single crystal grown by the top-seeded solution growth method. It has been clarified that the exothermic heat at the transition on cooling has more useful information than the endothermic heat on heating; in the cooling process two thermal anomalies occur separately at T1 and T2 although the transition is in a narrow temperature range. It is recognized from other methods that the nature of the transition on cooling is not of a single but of multiple steps. Resonant ultrasonic measurements using the “cell” were carried out, after developing a new excitation method. The sample does not have a simple softening approaching the transition point on cooling but has different elastic moduli for the two thermal anomalies at T1 and T2. The dielectric constant also has an intermediate constant value between T1 and T2. The crystal structure in the room temperature phase below the transition point has been determined by X-ray diffraction. In this region, tetragonal and monoclinic structures coordinating with each other exist.

Effect of Oxygen Cooling Environment on the Structural Characteristics and Dielectric Properties of BaTiO3 and SrTiO3 Thin Films

The BaTiO3 (BTO) and SrTiO3 (STO) thin films have been fabricated on (La,Sr)CoO3/MgO (100) single crystal substrate by pulsed laser deposition (PLD). The effect of oxygen content in the BTO and STO lattices on their structural characteristics and dielectric properties has been investigated. The variation of the oxygen content was made in BTO and STO thin (10 nm) films by changing oxygen cooling pressure from 10−3 Torr to 400 Torr. The lattice parameter of STO thin film was sensitive to the variation of the oxygen pressure while that of BTO thin film was not sensitive to the oxygen pressure. The volume of the STO thin film increased with decreasing the oxygen cooling pressure, which is attributed to the volume change caused by oxygen nonstoichiometry (deficiency). The dielectric constant of the STO thin film was insensitive to the oxygen cooling pressure. This result indicates that the dielectric constant of the STO thin film was not influenced by the oxygen deficiency, although the STO thin film was influenced by the oxygen environment and had oxygen deficient nonstoichiometry. Those results suggest that the lattice distortion is the most important factor to influence the dielectric property of specifically STO thin films. On the other hand, the BTO thin film was not susceptible to the change in the oxygen environment, resulting in insensitive lattice parameter and volume as well as the dielectric constant to the oxygen environment.

Dielectric Properties of BaTiO3 Based Lead Free Relaxor Prepared Through Conventional and Microwave Sintering

Dielectric ceramics with compositions belonging to the Ba(Nd x Ti1−2x Nb x )O 3 with varying concentration of x were prepared through Solid State Sintering route using both conventional and microwave sintering. The phase transformations were studied by dielectric measurements in a wide range of temperature and frequency. The relaxor behaviour is almost favoured as the composition deviates more from BaTiO 3 and as the substitution is heterovalent in the 6-coordination number crystallographic site.

Evaluation of Strain-Dependent Dielectric Properties in BaTiO3 ∕ LaNiO3 and ( Ba , Sr ) TiO3 ∕ LaNiO3 Artificial Superlattice Films on LaNiO3-Coated SrTiO3 Substrates

We formed strained artificial superlattices of and on -coated (001) substrates by dual-gun radio-frequency magnetron sputtering. The (00L) crystal truncation rod intensity profiles confirm the formation of a superlattice structure. The BTO (or BST) sublayer in the artificial superlattice is under biaxial compressive stress whereas the LNO sublayer is under biaxial tensile stress. Both and superlattices of total thickness exhibit some degree of strain relaxation, even though the modulation length is less than the critical value to generate misfit dislocations. These and artificial superlattices show a dielectric constant significantly enhanced relative to BTO and BST single layers of the same effective thickness. From a macroscopic point of view, the strain in the superlattice structure contributes significantly to the dielectric enhancement.

Effect of doping method on microstructural and defect profile of Sb–BaTiO 3

Electrical properties in BaTiO 3 based ceramics are strongly dependent on composition and microstructural development. In this work, we studied the effect of the particle coating as doping method on microstructure and electrical properties of Sb-doped BaTiO 3. The advanced doping method involved surface-coated BaTiO 3 particles with a thin film of a metal-organic precursor solution. Results were compared with the performance obtained on conventional doping method. The particle coating as doping method led to an effective grain growth inhibition as well as significant microstructure improvement. The incorporation of dopant into the perovskite lattice is influenced by the doping method. Results suggested that Sb acted as donor dopant on A or/and B sites, and also as acceptor on B sites, modifying the grain boundaries structure characteristics. Dopant incorporation method affected the defect structure, and therefore, the donor dopant concentration for the semiconductor insulator transition in BaTiO 3 ceramics.

Designing Gaussian basis sets to the theoretical study of the piezoelectric effect of perovskite (BaTiO 3)

Gaussian basis sets (24s14p, 30s19p14d, and 33s21p14d for O ( 3P), Ti ( 5S), and Ba ( 1S) atoms, respectively), are designed with the strategy of the Generator Coordinate Hartree-Fock method. The basis sets are then contracted to [6s4p], [10s5p4d], and [16s9p5d] to O, Ti, and Ba atoms, respectively, and used in calculations of total and orbital energies of 1TiO +2 and 1BaO fragments for quality evaluation in molecular studies. For O atom, the [6s4p] basis set is enriched with d polarization function and used along with the [10s5p4d] and [16s9p5d] basis sets for the theoretical study of the piezoelectric effect of perovskite (BaTiO 3). The results of this work evidence that the piezoelectric properties in BaTiO 3 can be caused by electrostatic interactions.

Modeling the Electrical and Optical Properties of BaTiO3 and LiNbO3 Single Crystals at Room Temperature

The electrical and optical properties of Barium Titanate BaTiO3 and lithium niobate LiNbO3 single crystals at room temperature are theoretically calculated by using a microscopic model based on the orbital approximation in correlation with the dipole-dipole interaction. We find that for LiNbO3 both the electronic polarizabilities and the electronic hyperpolarizabilities have to be considered in this calculation in order to match both the spontaneous polarization and refractive indices with experimental data. For BaTiO3 a description based an the electronic polarizability is sufficient.

Electrophysical Properties of Polymer Based Composites with Barium Titanate (BaTiO3)

Dielectric properties of BaTiO 3 composites with different polymer matrices were investigated in a wide range of frequencies and temperatures as a function of concentration, filler particles size and the method of composite preparation. The relations between the structure of composites and their electrophysical properties are analyzed.

Ferroelectric Properties of BaTiO3 Doped with La(Mg1/2Ti1/2)O3

BaTiO3 ceramics doped with 2.5 mol% of non-ferrolectric perovskite La(Mg1/2Ti1/2)O3 (BT:2.5%LMT) were dielectrically investigated at macroscopic and nanoscale (by Piezoresponse Force Microscopy) levels. The results of dielectric study performed on bulk ceramics were compared with those of individual grains. BT:2.5%LMT was revealed to exhibit the typical features of both ferroelectric and relaxor behaviour.

Effects of Sintering Temperature and Annealing in N2 Atmosphere on the Dielectric Properties of BaTio3 Based X7R Dielectric Materials

Two commercial BaTiO3 based powders were selected, characterized and used for the fabrication of X7R dielectric ceramics. The effects of forming and sintering on the dielectric properties have been studied and processing parameters optimized. The annealing treatment in N2 atmosphere has been used in order to modify the dielectric properties of BaTiO3. The related dielectric properties have been tested and microstructures of BaTiO3 ceramics examined. The results show that by combining the optimized processing parameters such as cold isostatic pressure 225 MPa, sintering temperature from 1300 to 1400 °C and annealing treatment at 850 °C, a marked increase in dielectric constant from approximately 3000 to 3600 has been achieved with the commercial BaTiO3 based powder. This was accomplished while keeping the X7R capacitor requirements on the dissipation factor (<2%) and temperature coefficient of capacitance (<±15%).

Hydrothermal Synthesis of Barium Titanate

Barium titanate fine particles were prepared by hydrothermal synthesis. The synthesis was preformed at a temperature between 75 and 180 °C and for 10 min to 96 h. The reactions were carried out in a strong alkaline solution. Ba(OH)2·8H2O was used as the Ba-precursor material. Various Ti precursors were used to investigate their effects on the properties of BaTiO3. The BaTiO3 powders were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, nitrogen sorption, and differential scanning calorimetry. XRD showed that the as-synthesized BaTiO3 powders have the BaTiO3 structure. The particle size of the Ti precursor has a strong influence on the size and morphology of barium titanate. The particle size of BaTiO3 was the largest when synthesized at 120 °C for 24 h by using anatase TiO2 (Merck) precursor. The particle size was about 0.1 μm when using TiO2 (70% anatase and 30% rutile, Degussa P25) or Ti(OH)4 as the precursor. The BaTiO3 powder was a porous structure when using Ti(OH)4 as the precursor. In addition, the particle size and morphology were dependent on the synthesis temperature. At 85 °C, the morphology of the powder was small crystal and an agglomerate of clusters. At 180 °C, the morphology of the powder was large (∼130 nm), uniform, and nearly monodisperse particles. Extending the synthesis time has no significant influence on the size and morphology.

Quantitative Analysis of the Effect of 90 Domain Walls on the Dielectric Properties of BaTiO 3 Single Grain

We quantitatively analyzed the effect of 90° domain walls on the dielectric properties of BaTiO 3 single grains. As a result, we experimentally clarified that the dielectric loss of a BaTiO 3 grain definitely increased in proportion to the sectional area of 90° domain walls existing in the grain. In addition, it was confirmed that the dielectric loss showed a marked dependence on the density of 90° domain walls existing in the grain.

Dielectric Properties of BaTiO3 Based Ceramics Prepared from Nano-powders

ABSTRACTIn this paper, the BaTiO3 nanoceramics have been fabricated by pressureless sintering for the first time. High purity BaTiO3 powders in nano-size of 50∼80nm synthesized by wet chemical method were used to fabricate nanoceramics. The addition of an appropriate amount of Nb2O5 and Co3O4 was found to suppress the grain growth, which is normally encountered in the conventional pressless sintering. The effects of Nb2O5 and Co3O4 on the phase structure, microstructure and dielectric properties of the sintered ceramics were investigated. The BaTiO3 ceramics with the average grain size less than 100nm were achieved after sintering below 1220°C with dielectric constant up to 2000 at room temperature, which is of cubic structure and meets the requirement of X7R specification.

Effect of the level of addition of Nb2O5/Co2O3 and Ba(Nb2/3Co1/3)O3 on the structure, microstructure, and dielectric properties of BaTiO3

In this work attempt is made to study the effects of the level of the addition of two dopant systems, that is, Nb2O5/Co2O3 and Ba(Nb2/3Co1/3)O3 on the structure, microstructure, and dielectric properties of BaTiO3(BT) prepared by ceramic route. For the BT samples doped with 2 and 3 at % Nb2O5/Co2O3 a broad maxima for er–T variations was observed. Higher levels of addition, that is, 6, 8, and 10 at % Nb2O5/Co2O3, however, caused a drastic reduction in the magnitude of er and vanishing of maxima peaks observed. The reduction in the magnitudes of the er for these samples is related to the observed reduction of the tetragonality of doped BT samples as well as the existence of some non-ferroelectric extra phase, evidenced by our XRD analysis. The existence of this extra phase is also believed to be mainly responsible for the observed increase of the dielectric loss. For the BT samples doped with Ba(Nb2/3Co1/3)O3 perovskite solid solution, the er maxima peak could only be detected for the samples doped with 2 at %. In the case of the samples doped with 4, 6, 8, and 10 at % perovskite solid solution, however, a very uniform distribution of er–T was observed. The increase of the level of dopant for these series of samples was also seen to give rise in the reduction of the magnitude of er. However, this reduction was not as strong as the cases observed for the samples doped with 8 and 10 at % Nb2O5/Co2O3. XRD patterns obtained for these series of samples also revealed the reduction of tetragonality of the BT samples when doped with Ba(Nb2/3Co1/3)O3. Further, microstructural studies carried out by scanning electron microscopy (SEM) on both series of samples revealed a contrasting picture. While a uniform grain size distribution was observed for the whole series of the samples doped with Ba(Nb2/3Co1/3)O3, a non-uniform size distribution of grain sizes was observed in the case of samples doped with Nb2O5/Co2O3. This is thought to be due to the possible formation and non-uniform distribution of a liquid phase due to the formation of Ti-rich region in the shell region of Nb2O5/Co2O3-doped samples. The existence of such liquid phase, in case of Nb2O5/Co2O3-doped samples, would have the consequence of an increased rate of diffusion of Nb/Co into the BT cores leaving narrow compositional fluctuations for the shell regions.

Influence of Ce doping on structure and properties of BaTiO3based X7R dielectrics

The effects of Ce doping on the lattice parameters, permittivity, and sintering characteristics of the BaTiO3-Nb2O5-Co2O3-Sm2O3-Li2CO3 system were studied. It was found that addition of CeO2 could improve dielectric properties at low or medium sintering temperatures. The structure, permittivity, and density of sintered ceramics were influenced by the vacancies introduced by donors and acceptors. Defect behaviour is also discussed.

Influence of the Oxygen Stoichiometry on the Structures and Ferroelectric Properties of BaTiO 3 Thin Films

We have investigated the influence of the oxygen stoichiometry on the structures, dielectric and ferroelectric properties of the BaTiO 3 thin films. The oxygen content in the films has a significant effect on lattice parameters, crystalline phase, crystallographic orientation, dielectric constant, dissipation factor, spontaneous polarization and polarization-electric field curves.

Influence of the Oxygen Stoichiometry on the Structures and Ferroelectric Properties of BaTiO 3 Thin Films

We have investigated the influence of the oxygen stoichiometry on the structures, dielectric and ferroelectric properties of the BaTiO 3 thin films. The oxygen content in the films has a significant effect on lattice parameters, crystalline phase, crystallographic orientation, dielectric constant, dissipation factor, spontaneous polarization and polarization-electric field curves.