BaTiO3 Compound Research Articles

Exploring the impact of hydrostatic pressure on the essential physical properties of BaTiO3 perovskite: A first principles quantum investigation and prospects for optoelectronic and thermoelectric applications

This research investigates how externally applied hydrostatic pressure ranging from 0 to 100 GPa impacts the cubic BaTiO3 perovskite compound through computational simulations. The results reveal that the bandgap value increases and shifts in the visible spectrum by applying pressures from 0 to 100 GPa. The absence of negative frequencies in the phonon dispersion confirms the dynamic stability of cubic BaTiO3 compound. The BaTiO3 maintains its cubic phase and exhibits remarkable mechanical stability with ductile behavior when subjected to high pressures. The optical properties of cubic BaTiO3 compound have been meticulously investigated utilizing complex dielectric function, complex refractive index, optical reflectivity, absorption coefficient, optical conductivity, and energy loss function across the energy spectrum up to 50 eV. The study identifies maximum absorption peaks in the UV region. So, cubic BaTiO3 compound under the effect of different pressures is suitable for broadly tunable phosphor material for energy-efficient w-LEDs, optoelectronic and thermoelectric applications.

Effects of oxygen group elements on thermodynamic stability, electronic structures and optical properties of the pure and pressed BaTiO3 perovskite

Thermodynamic stability, electronic structures, and optical properties of the pure and pressed BaTiO3 doped with different concentrations of oxygen group elements (Se, Te, and S) are investigated using the Density Functional Theory. It was found that when chalcogens elements in BaTiO3 compound substitute oxygen atoms, the forbidden gap is significantly decreased from 3.010 eV (for pressed BaTiO3) to 0.000 eV (for Te-doped BaTiO3 and pressed Se/Te-doped BaTiO3) indicating that chalcogens impurities have a crucial role in the reduction of the forbidden band of BaTiO3 compound. Moreover, 2.3% of compressive strain itself with and without the presence of chalcogens impurities transforms the pure BaTiO3 from indirect to direct semiconductor. Furthermore, the calculated formation energy confirms the thermodynamic stability of all studied compounds. Additionally, the doping changed the absorption behavior of BaTiO3 making the compound more useful for optoelectronic applications due to the introduction of addition carries into the system after the inclusion of chalcogens impurities.

Structural, optical, and electronic properties of barium titanate: experiment characterisation and first-principles study

ABSTRACT To study the structural, electronic, and optical properties of lead-free Barium titanate BaTiO3 (BT) ferroelectric material in its tetragonal structure, a combination of experimental and theoretical studies has been used and the obtained results were discussed. The studied BT compound was prepared via the sol–gel technique. The calculated bandgap energy (Eg) and structural parameters of BT are determined using four types of exchange–correlation functionals (PBE, PBEsol, LDA, and PW91) in the perspective of the density functional theory (DFT). XRD and Raman analysis have shown that BT ceramic exhibits a tetragonal phase structure without any trace of impurity phases. The UV–vis investigation showed that BT has a bandgap energy of 3.19 eV, which is larger than the theoretically calculated values. The computed lattice parameter c is overestimated (as large as ~1% deviation) when using the LDA approximation. In contrast, PBEsol proved that those lattice constants were close to the experimental values (a deviation of less than 1%).

Investigation of Ce doped BaTiO3 compound for optoelectronic devices

The full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT) is employed to probe the optical and electronic features of Ba1-xCexTiO3 (x = 0%, 5.55%, 12.5%, 25% and 50%) perovskite oxides. The effect of Ce doping on the band structure (BS) and optical spectra of cubic BaTiO3 compound has been explored. The outcomes of this work unveil the indirect-band semiconducting nature of Ba1-xCexTiO3(x = 0%), which becomes direct after Ce doping. Moreover, the width of band gap (Eg) narrows with the upsurge of Ce concentration in BaTiO3. The optical behavior of Ba1-xCexTiO3 compounds is estimated through refractive index, reflectivity, dielectric constant, optical conductivity and absorption coefficient. The controlled reduction in Eg of BaTiO3 with rise in concentration of Ce is a useful tool to make this compound promising for optical and optoelectronic devices.

Temperature dependent structural, dielectric, Raman, piezoresponse and photoluminescence investigations in sol-gel derived BCZT ceramics

0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 [50BZT-50BCT or BCZT] based compounds have been the focus of a lot of research, particularly motivated by their high piezoelectric effect. However, the literature lacks an elaborate investigation of the phase transition behavior in BCZT ceramics obtained by wet chemistry processing. Here, we present an in-depth study on the temperature dependence of x-ray diffraction (XRD), Raman scattering, dielectric properties, local piezoresponse and photoluminescence (PL) to investigate the sequence of phase transitions in the BCZT ceramic synthesized via a chemical route. Phase formation was determined by Rietveld analysis of XRD data, while compositional homogeneity and elemental quantification of the compound was validated using energy dispersive x-ray spectroscopy (EDX) and x-ray photoelectron spectroscopy (XPS) studies. Detailed fitting of XPS data indicated the existence of Ti3+ species (∼6%) in the prepared BCZT. Phase transitions were examined by analyzing the modifications in the XRD profile of Bragg reflection {200} and anomalies observed in the temperature variation of dielectric and Raman spectra studied over a wide temperature range starting from 10K to beyond Curie temperature. Crystallographic transformation temperatures obtained from dielectric measurement agreed well with those assessed from the temperature evolution of Raman spectra. In addition to other transitions, Raman scattering results revealed the existence of a transition from R3c to R3m phase near −175 °C, a transition that has not been interpreted in BCZT (and generally not observed in parent BaTiO3 compound). The luminescence response was studied by photoluminescence (PL) spectroscopy in the temperature range 15–300 K. The position of the PL peak was observed to shift with temperature and discontinuities in the wavelength shift were noted near phase transitions. Evolution of domain morphology with temperature was examined by piezoresponse force microscopy technique. Consolidated results assign the phase sequence in sol-gel derived BCZT as: R(R3c)→−175±10°CR(R3m)→−50±10°CO→40±10°CT→120±10°CC.

Synthesis of BaTiO3 Compound doped Ca and Gd Element Using Wet-Mixing Method

Synthesis of BaTiO3 Compound doped Ca and Gd Element Using Wet-Mixing Method

Synthesis and characterization of temperature stable low-loss (1−x)Mg(Ti0.95Sn0.05)O3–(x)BaTiO3 (0 ≤ x ≤ 0.1) ceramics for microwave applications

In the present work, we prepared (1−x)Mg(Ti0.95Sn0.05)O3–(x)BaTiO3 (0 ≤ x ≤ 0.1) solid-solutions via traditional solid-state reaction process and investigated their structural, optical, electrical, dielectric, and shielding properties. We report that these (1−x)Mg(Ti0.95Sn0.05)O3–(x)BaTiO3 compounds experienced structural phase transitions, wherein the tetragonal-structured BaTiO3 (space group P4mm) got transformed to monoclinic-structured Ba4Ti11O26 (space group C12/m1), and triclinic-structured Ba2Ti9O20 (space group P1). Interestingly, the Mg(Ti0.95Sn0.05)O3 showed no structural phase transition and was crystallized in its purest form without secondary phase formation. Additionally, the prepared compositions showed ten Raman active modes, and the relative density of all the samples exceeded 93.5%. The optical bandgap (Egap) values and DC conductivities of the samples were in the range of 3.82 eV–3.92 eV and 9.03 × 10−10 Sm−1–2.55 × 10−9 Sm−1, respectively. The composition 0.925 Mg(Ti0.95Sn0.05)O3–0.075BaTiO3 exhibited the best dielectric properties having relative permittivity (ɛr) of 19.69, loss tangent (tan δ) of 5.1 × 10−3, and temperature coefficient of resonant frequency (τf) of -8.5 ppm/°C at 1 MHz. In the Ku-band (12.4–18 GHz), this composition showed ɛr in the range of 14.62–15.49 and tan δ in the range of 2.85 × 10−2–5.89 × 10−2. An investigation of shielding properties in the Ku-band revealed that the prepared samples delivered average shielding effectiveness in the range of 5.98–6.65 dB. The prepared materials are proposed for microwave applications.

Electronic, optical, and thermoelectric properties of perovskite BaTiO3 compound under the effect of compressive strain

The theoretical effects of compressive strain on electronic, optical and thermoelectric properties for the cubic and tetragonal phases of BTO perovskite-type crystal have been investigated using Density Functional Theory (DFT). It was found that the compressive strain influences on the nature of the forbidden band of the cubic and tetragonal phases of BTO because by applying −2.3% or more of compressive strain, BTO becomes a semiconductor with a direct forbidden gap which eliminate the additional interaction in the CB which is a quite remarkable for photovoltaic devices. Furthermore, the values of forbidden gap width increase with increasing the percentage of compressive strain which shows the piezoelectric property of BTO. Moreover, the optical properties show that the pure and compressed BTO compounds are good materials for optical applications in both visible and UV spectrum. Additionally, the mobility of the holes grows with the compressive strain, which leads to increase the thermal and electrical conductivity of BTO.

Biferroic properties in Co-doped 0.2BaZrO3-0.8BaTiO3 materials

Combination in both ferroic properties in current lead-free ferroelectric materials is promising in creating a new type of smart electronic devices. In this report, single perovskite Co-doped 0.2BaZrO3-0.8BaTiO3 materials were synthesized by using the chemical method. The random incorporation of Co cations into the host lattice of 0.2BaZrO3-0.8BaTiO3 compounds resulted in distortion of the lattice parameter and strong reduction the optical band gap energy. Decreasing optical band gap energy was obtained from around 3.17 to 2.52 eV by introducing Co concentration of up to 9 mol.%. The magnetic properties of 0.2BaZrO3-0.8BaTiO3 compounds were showed in complex as dependent on the level of Co dopants. The nonlinear electrical polarization in 0.2BaZrO3-0.8BaTiO3 compounds was obtained and remained after the introduction of Co impurities. The observation in nonlinear in magnetism and electrical polarization were promised to transfer their materials for device applications.

Structural and transport properties of composite of La0.8Sr0.2MnO3 and BaTiO3 materials

We studied the effect of BaTiO3 phase on the structural, vibrational, and electrical properties of La0.8Sr0.2MnO3. The parent samples of La0.8Sr0.2MnO3, BaTiO3 and their composite (0.85) La0.8Sr0.2MnO3 + (0.15) BaTiO3 were synthesized by solid-state reaction route. Structural study using X-ray diffraction (XRD) for La0.8Sr0.2MnO3 phase revealed a rhombohedrally distorted (space group R3c) structure, while BaTiO3 compound was found to have crystallized in tetragonal structure (space group P4mm). The XRD results were verified using Rietveld refinement. The composite sample (0.85) La0.8Sr0.2MnO3 + (0.15) BaTiO3 display the presence of both of La0.8Sr0.2MnO3 and BaTiO3 phases. The addition of insulating BaTiO3 phase in the ferromagnetic metallic phase of La0.8Sr0.2MnO3 which exhibits well-characterized metal-to-insulator transition in the vicinity of 350 K enhances the resistivity and shifts the metal–insulator transition temperature TMI towards lower temperature. Further, with the application of magnetic field, resistivity of the composite sample is found to decrease and TMI in composite sample is observed to shift towards higher temperature. The magnetoresistance (MR) of composite sample (0.85) La0.8Sr0.2MnO3 + (0.15) BaTiO3 decreases monotonously in 200–300 K regime under magnetic field of 8 T. The analysis of electrical resistivity data in the metallic region (T TMI) is well described using Small polaron hopping (SPH) and Mott's variable range hopping (VRH) models.

Influence of distortions and tolerance factor on the structure of ABO3 type perovskites and complex perovskites

Variation of tolerance factor was observed with doping of Sr and Bi at A and B sites respectively and independently in BaTiO3 compound. Stability of NBT based compositions is varied with the substitution of Ba content in A-site and alters with the concentration. Combining with the electronegativity difference and octahedral factor of ABO3 structure, regularities governing the formation and the stability of perovskite type compounds are discussed. According to the results of BST and BBT series both dopants are reduce the tolerance factor and increase the distortion within the lattice of ABO3-type perovskite, the experience tolerance factor value and experience electronegativity difference value to form stable perovskite compound were obtained.

Structural and Magnetic Properties of Fe, Mn Co-doped BaTiO3 Synthesized Using Ball Milling Technique

Nano composite, monophasic nano-crystalline as well as bulk single phase materials of Fe, Mn co-doped BaTiO3 compounds are successfully synthesized through two different strategies using high energy meachnical attritor and muffle furnace. Significant changes in the structural properties such as formation of coexisting tetragonal, cubic and orthorhombic phases are brought out by varying post-processing temperature. A weak ferromagnetic signature is observed for nanocomposites and it ceased to exist with increasing post heating temperatures. Interestingly, superparamagnetic state is observed for nano-composites with blocking temperature of 263 K for a measurement field of 500 Oe. Further, this nanocomposite found to exhibit magnetic ordering well above room temperature which facilitates the possible interplay of multiple ferroic phases.

Lamellar and bundled domain rotations in barium titanate

Cross-correlation of electron backscatter diffraction patterns has been used to generate rotation maps of single crystals of tetragonal barium titanate (BaTiO3) containing multiple lamellae and bundles of ≈ 90° domains. Rotation measurement angular resolutions of 0.1 mrad (0.006°) and spatial resolutions of 30 nm are demonstrated on structures with approximately 1 μm domains extending over 10s of μm. The material orientations demonstrated considerable microstructural dependence: c domains, with polarization perpendicular to a free surface, exhibited little within-domain rotation variation while a-domains, with polarization parallel to the surface, exhibited considerable within-domain variation, particularly in the larger lamellar domain structure. In both lamellar and bundled structures, the maximum a–c between-domain rotation was approximately equal to the value θr ≈ 0.63° (11 mrad) predicted by a rigid rotation of tetragonal BaTiO3 unit cells across the domain boundary. However, in both structures there was gradual variation in rotation throughout, especially adjacent to domain boundaries, suggesting that a rigid rotation model predicts too abrupt a unit cell and polarization rotation. A new BaTiO3 compound defect was deduced through identification of a double integral surface rotation 2θr. The double rotation is indicative of a low-angle grain boundary terminating at a surface by a confined 90° domain.

Peculiar properties of phase transitions in Na0.5Bi0.5TiO3−0.06BaTiO3 lead-free relaxor ferroelectrics seen via acoustic emission

Na[Formula: see text]Bi[Formula: see text]TiO3-0.06BaTiO3 relaxor ferroelectrics (RFEs) ceramic samples were investigated by means of dielectric and acoustic emission methods in the temperature range of 70–350[Formula: see text]C and in dependence on frequency. Dielectric curve exhibits two anomalies: strongly dispersive the local maximum, within 130–180[Formula: see text]C and slightly dispersive the smeared high-temperature maximum within 300–310[Formula: see text]C. Acoustic emission exhibits the five groups of bursts: near 123[Formula: see text]C, 150–180[Formula: see text]C, near 225[Formula: see text]C, 300–310[Formula: see text]C and 327[Formula: see text]C. The first and third groups of acoustic emission bursts correspond to phase transitions of R[Formula: see text]c-P[Formula: see text]bm phases coexisting in this temperature, range, while the fourth and fifth groups of acoustic emission bursts correspond to P[Formula: see text]bm-P[Formula: see text] /mbm-Pm[Formula: see text] m phase transitions. The second group of acoustic emission bursts corresponds to strongly dispersive local maximum at which no phase transition has been proved in Na[Formula: see text]Bi[Formula: see text]TiO3-0.06BaTiO3. The existence and the location of the intermediate temperature, [Formula: see text], in Na[Formula: see text]Bi[Formula: see text]TiO3-0.06BaTiO3 compound are discussed.

Improved magnetic properties and structural characterizations in Mn doped 0.9BiFeO3–0.1BaTiO3 compositions

A structurally correlated magnetization enhancement is reported for Mn doped 0.9BiFeO3–0.1BaTiO3 compounds. X-ray diffraction and Rietveld refinement studies revealed a distorted perovskite structure with the coexistence of rhombohedral and monoclinic symmetries. Mössbauer spectroscopy results showed a magnetic spectral signature of ordered Fe3+ ions for the rhombohedral phase of the undoped sample, and for both rhombohedral and monoclinic phases of the Mn doped samples. A significant magnetization increase (reaching 0.50emu/g), associated to the magnetic ordering of the Cm phase and to the retention of the Mn3+ valence state, was observed for Mn doped samples.

Influence of milling duration on microstructural, electrical, ferroelectric and piezoelectric properties of Ba0.9Sr0.1Zr0.04Ti0.96O3 ceramic

In an effort to explore lead-free ferroelectric ceramic material for capacitor applications, the Sr and Zr co-doped BaTiO3 compound has been selected for investigation. A detailed study was carried out to study the effect of mechanical milling duration on structure, particle size, morphology, dielectric and piezoelectric properties. The Ba0.9Sr0.1Zr0.04Ti0.96O3 ceramics were synthesized using mechanochemical activation technique for different milling duration of 25, 30, 35, 40 and 45h. The Rietveld refinement analysis of X-ray diffraction pattern confirms the formation of tetragonal phase with P4mm space group for all the samples. When subjected to long duration mechanical milling, the samples have shown different grain size distribution. The average grain size reduces from 931nm to 385nm on increasing the milling duration from 25h to 45h. Ferroelectric studies reveal that the saturation and remnant polarization were found maximum for 35h milled sample. Furthermore, piezoelectric constant, d33 were also found to be maximum for 35h milled sample. The presence of Sr and Zr in barium titanate combined with optimized milling conditions may provide significant technological advances in the field of BaTiO3 based ferroelectric devices.

Magnetoelectric effect probe through ppm Fe doping in BaTiO3

The nominal BaTiO3 compound often exhibits an assortment of controversial magnetic signals which can be simply explained through minute presence of spurious magnetic elements in the perovskite matrix, even when this compound is synthesized from high grade Ba and Ti precursors. Proton Induced X-Ray Emission (PIXE) technique enable to confirm ∼100 ppm of Fe contaminant which masks the utterly BaTiO3 diamagnetism. Nevertheless, besides the expected paramagnetism of highly diluted Fe ions, it is also possible to observe a cooperative magnetic moment signature which exhibits an intricate relation with the phase transitions of the BaTiO3 matrix. Such magneto-electric coupling signature is further corroborated by Raman spectroscopy, dielectric and X-ray diffraction measurements, indicating to a partial segregation of a rich Fe oxide phase, having a local structure clamped to the perovskite crystallites, hence acting as a practical probe sensitive to the local structural transitions of the host material.

Theoretical Approach to the CH4 Decomposition on BaTiO3(001)

Oxide configurations with perovskite structures exhibit some interesting and controllable properties. BaTiO3 compounds have attracted considerable attention due to their potential use as electric and optical applications (1). Additionally, BaTiO3 has been studied for its catalytic properties in the oxidative coupling of methane (2), partial oxidation of methane (3) and for the total oxidation of methane (4) showing some promising results. Moreover, the presence of BaTiO3 on the anode material showed to suppress the C deposition for the low temperature dry methane reforming (5). In a similar way, BaTiO3 has been used as anode for solid oxide fuel cells (SOFCs) exhibiting quite low performance when methane was employed as fuel, but its performance increased in the presence of sulfur containing fuel (6). Although, this material showed some curious properties when used partially or totally as anode for SOFCs to date there are only speculations regarding its potential. In several occasions theoretical studies have been used to elucidate the phenomena behind some exciting properties such as catalytic behaviour. However, this is not any easy task since heterogeneous catalytic processes are complex to model due to the absence of information on the molecule-surface interaction, and the effect that the operating conditions and catalyst preparation have on its performance. In this work an idealized model will be used to describe the methane decomposition on the surfaces of BaTiO3(001) employing density functional theory (DFT) method. Preliminary results show that the TiO2-terminated surface is approximately four times more active for the total decomposition of methane than the BaO-terminated surface. References S. Saha, T. P. Sinha, and A. Mookerjee, Phy. Rev. B, 62, 8828, (2001). M. Teymouri, and E. Bagherzadeh, J. Mat. Sci., 30, 3005, (1995). C. Guo, J. Zhang, W. Li, P. Zhang, and Y. Wang, Cat. Today, 98, 583, (2004). I. Popescu, A. Urda, T. Yuzhakova, I. Marcu, J. Kovacs, and I. Sandulescu, C. R. Chimie, 12, 1072, (2009). X. Li, Q. Hu, Y. Yang, Y. Wang, and F. He, Appl. Catal. A: General, 413– 414, 163, (2012). J. H. Li, X. Z. Fu, J. L. Luo, K. T. Chuang and A. R. Sanger, J. Power Sources, 213, 69 (2012).

Structure and Properties of Bi<sub>0.5</sub>Na<sub>0.5</sub>TiO<sub>3</sub>-BaTiO<sub>3</sub> Compound Ceramics

The Bi0.5Na0.5TiO3-xwt%BaTiO3 compound ceramics were prepared. The influence of different BaTiO3 content on structure was evaluated by scanning electron microscopy and X-ray diffraction analysis. The results show oriented is induced by plate-like BaTiO3 template. Signficant improvement of the piezoelectric (d33 = 112 pC/N) and dielectric properties ( max ≈ 5500) was observed. The improvement was attested to the apparent alignment of the BaTiO3 templates and grain oriented growth.

Fluctuations, higher order anharmonicities, and Landau expansion for barium titanate

The correct description of the ferroelectric phase transition in barium titanate requires that, in the expansion of the free energy, not only the sixth-order terms but also the eighth-order terms should be retained. One more unusual feature of the BaTiO3 compound is that the coefficients B 1 and B 2 of the terms P 4 x and P 2 x P 2 y in the Landau expansion depend on the temperature. It is demonstrated that the temperature dependence of the coefficients B 1 and B 2 can be associated with the thermal fluctuations of polarization under conditions where the fourth-order anharmonic constants are anomalously small; i.e., a nonlinearity of the type P 4 and higher order anharmonicities make comparable contributions. Regular (noncritical) fluctuation contributions to the coefficients B 1 and B 2 are calculated to the first order in the sixth- and eighth-order anharmonic constants. Both contributions increase monotonically with increasing temperature, which is in agreement with the experimental dependences of these coefficients. The proposed theory without additional assumptions makes it possible to determine the ratio of the fluctuation components of the coefficients B 1 and B 2. This ratio also appears to be very close to that observed in the experiment.