Phase Transition In BaTiO3 Research Articles

Statistical model for the description of ferroelectric phase transitions in BaTiO3 and KNbO3

Statistical model for the description of ferroelectric phase transitions in BaTiO₃ and KNbO₃

Field dependence of the electrocaloric effect in BaTiO3 and Ba(Zr0.12Ti0.88)O3: High-resolution measurements around the phase transition

The electric field dependence of the electrocaloric effect is investigated in BaTiO3 and Ba(Zr0.12Ti0.88)O3 by a direct method with sub-mK temperature resolution. The field dependence of the caloric temperature change ΔT(E) shows a pronounced change within a few Kelvin around the Curie temperature for the first-order phase transition in BaTiO3. The transition from a linear field dependence in the ferroelectric phase over a butterfly-shaped to a quadratic field dependence in the paraelectric phase is compared to predictions of Landau–Devonshire theory. The simultaneous measurement of caloric and dielectric properties further allows for the investigation of the polarization dependence ΔT(P) of the electrocaloric effect. We find clear deviations from the predicted quadratic polarization dependence for temperatures close to the Curie temperature. Ba(Zr0.12Ti0.88)O3 shows in contrast only a slow and gradual change of the field dependence over a broad temperature range as a consequence of its diffuse phase transition.

Stabilization of the first-order phase transition character and enhancement of the electrocaloric effect by Na0.5Bi0.5TiO3 substitution in BaTiO3 ceramics

First-order character of the ferroelectric phase transition in BaTiO3 (BT) is maintained by Na0.5Bi0.5TiO3 (NBT) substitution, which in turn causes large electrocaloric response.

Electrocaloric effect in BaTiO3 multilayer capacitors with first-order phase transitions

Electrocaloric (EC) materials, presenting large adiabatic temperature change or isothermal entropy change under the application (or removal) of electric fields, offer an efficient alternative to caloric heat pumps for replacing hazardous gases used in traditional vapor-compression systems. Recently, a large EC temperature change of 5.5 K have been reported in Pb(Sc0.5Ta0.5)O3 multilayer ceramic capacitors (Nair et al 2019 Nature 575 468) thanks to its strong first-order phase transition and a temperature span of 13 K has been reported in a prototype based on these capacitors (Torelló et al 2020 Science 370 125). However, the toxicity of lead forces researchers to find eco-friendly materials exhibiting competitive EC performances. Here, we study the EC effect in lead-free BaTiO3 multilayer capacitors using an infrared camera. Unlike commercial BaTiO3 capacitors, we prepared our samples without sacrifying the first-order phase transition in BaTiO3 while a low amount of 0.2 mol% Mn was added as an acceptor dopant to improve electrical resistivity. Their EC adiabatic temperature variations show two peaks versus temperature, which match BaTiO3 two first-order phase transitions, as observed by differential scanning calorimetry. We measured a temperature drop of ∼0.9 K over a temperature range of 70 K under 170 kV cm−1, starting at 30 °C near the tetragonal-to-orthorhombic phase transition. Under the same electric field, a maximum temperature change of 2.4 K was recorded at 126 °C, at BaTiO3’s Curie temperature. Our findings suggest that further optimized BaTiO3 capacitors could offer a path for designing lead-free caloric cooling prototypes.

Nanostructure Mediated Piezoelectric Effect of Tetragonal BaTiO3 Coatings on Bone Mesenchymal Stem Cell Shape and Osteogenic Differentiation.

In recent years, porous titanium (Ti) scaffolds with BaTiO3 coatings have been designed to promote bone regeneration. However, the phase transitions of BaTiO3 have been understudied, and their coatings have yielded low effective piezoelectric coefficients (EPCs < 1 pm/V). In addition, piezoelectric nanomaterials bring many advantages in eliciting cell-specific responses. However, no study has attempted to design a nanostructured BaTiO3 coating with high EPCs. Herein, nanoparticulate tetragonal phase BaTiO3 coatings with cube-like nanoparticles but different effective piezoelectric coefficients were fabricated via anodization combining two hydrothermal processes. The effects of nanostructure-mediated piezoelectricity on the spreading, proliferation, and osteogenic differentiation of human jaw bone marrow mesenchymal stem cells (hJBMSCs) were explored. We found that the nanostructured tetragonal BaTiO3 coatings exhibited good biocompatibility and an EPC-dependent inhibitory effect on hJBMSC proliferation. The nanostructured tetragonal BaTiO3 coatings of relatively smaller EPCs (<10 pm/V) exhibited hJBMSC elongation and reorientation, broad lamellipodia extension, strong intercellular connection and osteogenic differentiation enhancement. Overall, the improved hJBMSC characteristics make the nanostructured tetragonal BaTiO3 coatings promising for application on implant surfaces to promote osseointegration.

History dependence of avalanche dynamics of ferroelectric phase transition in BaTiO3 under external bias field

A ferroelectric phase transition under an external bias electric field after field cooling and zero field cooling in barium titanate single crystals shows scale invariant nucleation and growth of complex domain structures. The avalanche energy exponents vary with the external bias, depending on the cooling history of the sample under applied field or zero field cooling. After field cooling, resulting in a single domain sample, the energy exponent is near the integrated mean field value of 5/3, namely, 1.68 ± 0.022. The sample after field cooling shows the same exponent with an external bias electric field range of up to 4.5 kV/cm. The exponent of a multi-domain sample, after zero field cooling, decreases from ε = 1.85 to the fixed point of 1.66 under high fields. The different behavior is attributed to the greater complexity of domain patterns in the multi-domain sample, which reduces to a single domain state under strong applied fields. Compared with the single-domain state, the multi-domain state has more domain boundaries and the intersections formed by these domain boundaries. These domain boundaries and their intersections will hinder the movement of the phase boundary and act as a pinning effect on the front of the phase interface. The effect is to generate more small energy signals, making the critical exponent high. At the same time, the aftershock time distribution (Omori law) remains the same for all switching conditions with an Omori exponent near −1 and switching time correlations of −1 ± 0.05 for short times (&amp;lt;1 s) and −2 ± 0.10 for long times (&amp;gt;1 s).

Determination of the temperature dependences of the coefficients of the elastic compliance tensor and the elasticity tensor in the tetragonal phase BaTiO3

A regression analysis of the temperature dependences of the elastic compliance coefficients in the tetragonal phase BaTiO3 has been carried out. Two functions are proposed that have critical temperatures, one of which corresponds to the second to the rest of the coefficients From the obtained analytical dependences, the temperature dependences of the elasticity tensor components in the tetragonal phase are calculated. Formulas for determining the effective coefficient of elasticity and the effective coefficient of elastic compliance are proposed. It is shown that has minims in the near of structural phase transitions in BaTiO3.

Decoding the Mechanisms of Phase Transitions from In Situ Microscopy Observations.

Analysis of the temperature- and stimulus-dependent imaging data toward elucidation of the physical transformations is an ubiquitous problem in multiple fields. Here, temperature-induced phase transition in BaTiO3 is explored using the machine learning analysis of domain morphologies visualized via variable-temperature scanning transmission electron microscopy (STEM) imaging data. This approach is based on the multivariate statistical analysis of the time or temperature dependence of the statistical descriptors of the system, derived in turn from the categorical classification of observed domain structures or projection on the continuous parameter space of the feature extraction-dimensionality reduction transform. The proposed workflow offers a powerful tool for the exploration of the dynamic data based on the statistics of image representation as a function of the external control variable to visualize the transformation pathways during phase transitions and chemical reactions. This can include the mesoscopic STEM data as demonstrated here, but also optical, chemical imaging, etc., data. It can further be extended to the higher dimensional spaces, for example, analysis of the combinatorial libraries of materials compositions.

Comment on “Novel Insight on the Phase Transition of BaTiO3 Based on Structural Evidence and Heat Flow Measurement”

Comment on “Novel Insight on the Phase Transition of BaTiO₃ Based on Structural Evidence and Heat Flow Measurement”

Influence of pressure on the kinetics of ferroelectric phase transition in BaTiO3

The ferroelectric phase transition in barium titanate under pressure was studied within the framework of Landau – Ginzburg theory using differential scanning calorimetry. An innovative method for high-sensitive thermal measurements under pressure was demonstrated. It was shown that the relaxation process proceeds nonmonotonically with the formation of intermediate short-lived phases. It was established that polydomain ordering is preferred but the monodomenization of the sample is possible under certain conditions. A narrowing of the temperature hysteresis with increasing pressure was revealed. A new tricritical point in barium titanate crystals characterizing the changing of the phase transition has been experimentally determined and theoretically confirmed.

Strain-Induced Magnetoelectric Coupling in Fe3O4/BaTiO3 Nanopillar Composites.

Magnetoelectric coupling properties are limited to the substrate clamping effect in traditional ferroelectric/ferromagnetic heterostructures. Here, Fe3O4/BaTiO3 nanopillar composites are successfully constructed. The well-ordered BaTiO3 nanopillar arrays are prepared through template-assisted pulsed laser deposition. The Fe3O4 layer is coated on BaTiO3 nanopillar arrays by atomic layer deposition. The nanopillar arrays and heterostructure are confirmed by scanning electron microscopy and transmission electron microscopy. A large thermally driven magnetoelectric coupling coefficient of 395 Oe °C-1 near the phase transition of BaTiO3 (orthorhombic to rhombohedral) is obtained, indicating a strong strain-induced magnetoelectric coupling effect. The enhanced magnetoelectric coupling effect originated from the reduced substrate clamping effect and increased the interface area in nanopillar structures. This work opens a door toward cutting-edge potential applications in spintronic devices.

Symmetry-adapted pair distribution function analysis (SAPA): a novel approach to evaluating lattice dynamics and local distortions from total scattering data.

A novel symmetry-adapted pair distribution function analysis (SAPA) method for extracting information on local distortions from pair distribution function data is introduced. The implementation of SAPA is demonstrated in the TOPAS-Academic software using the freely available online software ISODISTORT, and scripts for converting the output from ISODISTORT to a SAPA input file for TOPAS are provided. Finally, two examples are provided to show how SAPA can evaluate the nature of both dynamic distortions in ScF3 and the distortions which act as an order parameter for the phase transitions in BaTiO3.

Effect of low temperature structural phase transitions in BaTiO3 on electrical transport through a metal–ferroelectric–metal multilayer of AuCr/BaTiO3/Nb:SrTiO3

In this paper we report an investigation of electronic transport through the metal–ferroelectric–metal (MFM) multilayer consisting of AuCr/BaTiO3/Nb:SrTiO3 over a temperature range of 100 K–300 K where BaTiO3 (BTO) shows a series of structural phase transitions leading to change of magnitude as well as the orientation of the polarization . We observed that the bias dependent barrier heights associated with the interfaces carry strong signature of the phase transitions in the BTO layer which lead to a strong temperature dependent asymmetric transport, when cooled down below room temperature. Specifically, it is observed that the temperature dependence is closely correlated to low temperature transitions in the BTO layer as revealed through the temperature dependent x-ray diffraction (XRD), capacitance as well as resistivity behavior of the BTO layer. There is substantial enhancement of the asymmetry in the device current that occurs at or close to temperatures T 2 ∼ 190 K where BTO shows a crystallographic phase change to the low temperature rhombohedral phase. The temperature dependent changes occur due to barrier modulation at the interfaces of AuCr/BaTiO3 as well as BaTiO3/Nb:SrTiO3 that softens on cooling due to inhomogenities present there. The change in barrier on change of the bias direction has been observed below T 2 which arises from alignment of the polarization in-plane or out-of-plane as determined by tensile or compressive character of the in-plane strain in the BTO film. We also discuss the effect of space charge determined by the oxygen vacancies in the interface region, regulated by the applied bias.

Exotic magnetic properties and enhanced magnetoelectric coupling in Fe3O4-BaTiO3 heterostructures

In the present work, magnetoelectric composites of Fe3O4 and BaTiO3 were successfully synthesized with 0–3 and 1–3 connectivity. In Fe3O4-BaTiO3 composites with 1–3 connectivity, the M-H loop analysis shows the presence of the isotropic point, whereas the M-T measurements of both samples reveal a unique downturn anomaly in the Curie-Weiss plot, indicating the presence of a Griffiths-like phase. The cluster glass nature of Fe3O4 nanostructures leads to the formation of exchange bias in the investigated ME composites. The different phase transitions of BaTiO3 are visible in the M(T) data as a consequence of magnetoelectric coupling between Fe3O4 and BaTiO3. The maximum magnetoelectric coupling coefficients observed for the Fe3O4-BaTiO3 composites with 0–3 and 1–3 connectivity are 8.34 mV cm−1 Oe−1 and 28.78 mV cm−1 Oe−1, respectively; both values are higher than that of the previously reported values of Fe3O4-BaTiO3 composites. Further, the magnetoelectric coupling coefficients of Fe3O4-BaTiO3 1–3 composites show an increasing trend towards the BaTiO3 rich phase.

Challenges and Applications to Operando and In Situ TEM Imaging and Spectroscopic Capabilities in a Cryogenic Temperature Range.

ConspectusIn this Account, we describe the challenges and promising applications of transmission electron microscopy (TEM) imaging and spectroscopy at cryogenic temperatures. Our work focuses on two areas of application: the delay of electron-beam-induced degradation and following low-temperature phenomena in a continuous and variable temperature range. For the former, we present a study of LiMn1.5Ni0.5O4 lithium ion battery cathode material that undergoes electron beam-induced degradation when studied at room temperature by TEM. Cryogenic imaging reveals the true structure of LiMn1.5Ni0.5O4 nanoparticles in their discharged state. Improved stability under electron beam irradiation was confirmed by following the evolution of the O K-edge fine structure by electron energy-loss spectroscopy. Our results demonstrate that the effect of radiation damage on discharged LiMn1.5Ni0.5O4 was previously underestimated and that atomic-resolution imaging at cryogenic temperature has a potential to be generalized to most of the Li-based materials and beyond. For the latter, we present two studies in the imaging of low-temperature phenomena on the local scale, namely, the evolution of ferroelectric and ferromagnetic domains walls, in BaTiO3 and Y3Fe5O12 systems, respectively, in a continuous and variable temperature range. Continuous imaging of the phase transition in BaTiO3, a prototypical ferroelectric system, from the low-temperature orthorhombic phase continuously up to the centrosymmetric high-temperature phase is shown to be possible inside a TEM. Similarly, the propagation of domain walls in Y3Fe5O12, a magnetic insulator, is studied from ∼120 to ∼400 K and combined with the application of a magnetic field and electrical current pulses to mimic the operando conditions as in domain wall memory and logic devices for information technology. Such studies are promising for studying the pinning of the ferroelectric and magnetic domains versus temperature, spin-polarized current, and externally applied magnetic field to better manipulate the domain walls. The capability of combining operando TEM stimuli such as current, voltage, and/or magnetic field with in situ TEM imaging in a continuous cryogenic temperature range will allow the uncovering of fundamental phenomena on the nanometer scale. These studies were made possible using a MEMS-based TEM holder that allowed an electron-transparent sample to be transferred and electrically contacted on a MEMS chip. The six-contact double-tilt holder allows the alignment of the specimen into its zone axis while simultaneously using four electrical contacts to regulate the temperature and two contacts to apply the electrical stimuli, i.e., operando TEM imaging. This Account leads to the demonstration of (i) the high-resolution imaging and spectroscopy of nanoparticles oriented in the desired [110] zone-axis direction at cryogenic temperatures to mitigate the electron beam degradation, (ii) imaging of low-temperature transitions with accurate and continuous control of the temperature that allowed single-frame observation of the presence of both the orthorhombic and tetragonal phases in the BaTiO3 system, and (iii) magnetic domain wall propagation as a function of temperature, magnetic field, and current pulses (100 ns with a 100 kHz repetition rate) in the Y3Fe5O12 system.

Novel Insight on the Phase Transition of BaTiO3 Based on Structural Evidence and Heat Flow Measurement

Reexamination of the 403 K phase transition of BaTiO3 by X-ray and calorimetric studies clarified that the formation and annihilation processes of monoclinic minor domains at the phase transition a...

Imaging microstructural dynamics and strain fields in electro-active materials in situ with dark field x-ray microscopy.

The electric-field-induced and temperature induced dynamics of domains, defects, and phases play an important role in determining the macroscopic functional response of ferroelectric and piezoelectric materials. However, distinguishing and quantifying these phenomena remains a persistent challenge that inhibits our understanding of the fundamental structure-property relationships. In situ dark field x-ray microscopy is a new experimental technique for the real space mapping of lattice strain and orientation in bulk materials. In this paper, we describe an apparatus and methodology for conducting in situ studies of thermally and electrically induced structural dynamics and demonstrate their use on ferroelectric BaTiO3 single crystals. The stable temperature and electric field apparatus enables simultaneous control of electric fields up to ≈2 kV/mm at temperatures up to 200 °C with a stability of ΔT = ±0.01 K and a ramp rate of up to 0.5 K/min. This capability facilitates studies of critical phenomena, such as phase transitions, which we observe via the microstructural change occurring during the electric-field-induced cubic to tetragonal phase transition in BaTiO3 at its Curie temperature. With such systematic control, we show how the growth of the polar phase front and its associated ferroelastic domains fall along unexpected directions and, after several cycles of electric field application, result in a non-reversible lattice strain at the electrode-crystal interface. These capabilities pave the way for new insights into the temperature and electric field dependent electromechanical transitions and the critical influence of subtle defects and interfaces.

Structural, ferroelectric and photocatalytic performance of Ba1-xCaxTiO3 ceramics

Ba1-xCaxTiO3 (Ca added BaTiO3; x = 0–0.3) ceramics is used as a target catalyst to probe the influence of ferro-electricity on the de-colorization of a typical dye molecule Methyl orange under visible light irradiation. The results indicated that there is a two fold increase in the de-colorization rate using Ba0.7Ca0.3TiO3 in around 180 min. This is ascribed to the ferro-electricity of the tetragonal phase. To probe the ferro-electricity in the catalyst, the P-E hysteresis loops show high polarization of 17.50 µC/cm2 in x = 0.3 compared to 10 µC/cm2 for x = 0 at 303 K. The high value of polarization in Ca added BaTiO3 enhances ferro-electricity and ensures a tightly bound layer of dye molecule and also acts to separate the photo-excited carriers due to the internal space charge layer. Both these features act to enhance the catalytic performance. Further, we studied the temperature dependence of dielectric study and it was found that dielectric constant increased and undergoes a maximum corresponding to a phase transition (330 K for x = 0.3) and thereafter decreased. The Ca substitution diffused the phase transition of BaTiO3 and resulted in shift of transition temperature towards room temperature with increase in content of Ca which is useful for many dielectric applications.

Periodicity-Doubling Cascades: Direct Observation in Ferroelastic Materials.

Very sensitive responses to external forces are found near phase transitions. However, transition dynamics and preequilibrium phenomena are difficult to detect and control. We have observed that the equilibrium domain structure following a phase transition in ferroelectric and ferroelastic BaTiO_{3} is attained by halving of the domain periodicity multiple times. The process is reversible, with periodicity doubling as temperature is increased. This observation is reminiscent of the period-doubling cascades generally observed during bifurcation phenomena, and, thus, it conforms to the "spatial chaos" regime earlier proposed by Jensen and Bak [Phys. Scr. T 9, 64 (1985)PHSTER0281-184710.1088/0031-8949/1985/T9/009] for systems with competing spatial modulations.

Study on piezoelectric, dielectric and dispersive phase transition of BaTiO3–BaZrO3–CaTiO3 ceramics

The dielectric, piezoelectric properties and dispersive ferroelectric phase transitions of (0.84 − x) BaTiO3–0.16CaTiO3–xBaZrO3 ternary ceramics were investigated in this manuscript. The study found that the optimum BaZrO3 doping amount was 0.1 mol%. Compared to the binary system, the ternary system has a denser microstructure and a more uniform grain size, and more excellent electrical properties. The influence mechanism of BaZrO3 doping on the system was explained in detail by lattice theory and domain theory.