BaZrO3 Films Research Articles

Stereointerface Structure Drives Ferroelectricity in BaZrO3 Films.

Interfacial strain engineering can induce structural transformation and introduce new physical properties into materials, which is an effective method to prepare new multifunctional materials. However, interfacial strain has a limited spatial impact size. For example, in 2D thin films, the critical thickness of biaxial strain is typically less than 20 nm, which is not conducive to the maintenance of a strained structure and properties in thick film materials. The construction of a 3D interface can solve this problem. The large lattice mismatch between the BaZrO3 thin film and the substrate can induce the out-of-phase boundary (OPB) structure, which can extend along the thickness direction with the stacking of atoms. The lattice distortion at the OPB structure can provide a clamping effect for each layer of atoms, thus expanding the spatial influence range of biaxial strain. As a result, the uniform in-plane strain distribution and strain-induced ferroelectricity (Pr = 13 μC/cm2) are maintained along the thickness direction in BaZrO3 films.

Synthesis of crystalline BaZrO3 thin films over preferred-oriented ZrN by a hydrothermal-galvanic couple method for photoelectrochemical evaluations

Crystalline barium zirconate (BaZrO 3 ; BZO) films which could be applied to photoelectrochemical cells and fuel cells were synthesized by a hydrothermal-galvanic couple (HT–GC) method using preferred-oriented ZrN thin-film electrodes. The HT–GC synthesis was carried out at 90°C in alkaline solutions. Substantial galvanic currents were detected without applying any external power sources throughout the synthesis. X-ray diffraction patterns reveal that BZO films with different crystallinities were achieved by such a facile synthesis. Moreover, the BZO films that grew on close-packed (200)-preferred oriented ZrN underlayer exhibited higher crystallinity and growth rates than on the (111)-preferred oriented ZrN. The obtained BZO films exhibited fast on-off photoelectrochemical responses while the BZO films with higher crystallinity over the (200)-ZrN possessed better photoelectrochemical responses. • Crystalline BaZrO3 films could be synthesized on ZrN by a hydrothermal-galvanic couple method • Crystallinity and photoelectrochemical performance of the films were tailored through ZrN • Galvanic effects were enhanced by using (200)-oriented ZrN rather than (111) oriented ZrN • Higher crystallinity of the films could be achieved by a more close-packed (200)-ZrN • Better and fast on-off photoelectrochemical responses of the films were obtained by (200)-ZrN

Switchable diode effect in BaZrO3 thin films

Oxygen deficient BaZrO3 films with bi-layered structures show switchable diode effects. Both oxygen vacancies and grain boundaries play important parts.

Influences of BaZrO3 particles on the microstructure and flux pinning of YBCO film prepared by using modified TFA-MOD approach

YBa2Cu3Oy (YBCO) films with BaZrO3 (BZO) particles were fabricated on LaAlO3 (00l) single crystal substrates by benzoate modified trifluoroacetate metal organic deposition (modified TFA-MOD). The influences of BZO particles on the texture, microstructure and the flux pinning properties of YBCO films were discussed. At high level of BZO doping, the BZO particles were considered to play an important role in the formation of a-axis oriented YBCO grains and the degradation of texture. When the optimal BZO content was 5%, the BZO particles as the flux pinning centers could significantly improve the critical current density (Jc) and flux pinning force (Fp) of BZO-doped YBCO film. Jc value of YBCO + 5%BZO film was about 4.9 MA/cm2 at 77 K and 0 T, and the highest Fp value (Fpmax) was about 4.3 GN/m3 at 77 K.

The Vortex Path Model Analysis of the Field Angle Dependence of the Critical Current Density in Nanocomposite YBa2Cu3 O 7−x – BaZrO3 Films Obtained by Low Fluorine Chemical Solution Deposition

In the present paper, we analyze the role of in situ grown BaZrO3 (BZO) inclusions in YBa2Cu3O7−x (YBCO) thin films prepared by chemical solution deposition using a low fluorine coating solution, on the field angle dependence of the critical current density, J c (𝜃), data using the vortex path model. In order to form a coherent picture on the BZO doping influence on the pinning properties of the YBCO matrix, detailed structural analyses performed by X-ray diffraction techniques and microstructural evaluation by transmission electron microscopy are also presented. The evaluation of different contributions to the overall, J c , permitted us to prove the effectiveness of the BZO inclusions acting as isotropic pinning centers, reflected in a uniform component of high relative value with respect to other components. For the studied 10 mol % BZO doping concentration, a threefold increase in the critical current density, J c , of the YBCO host is measured, in self-field at 77 K, corresponding to a value of J c =2.9MA/cm2, whereas a factor 10 is measured at 1 T (J c =0.35 MA/cm2).

Microstructural characterization of TFA-MOD processed Y1−xGdxBa2Cu3O7−y with BaZrO3

Y1−xGdxBa2Cu3O7−y with BaZrO3 film was fabricated on CeO2 buffered LaMnO3/ion beam assisted deposition-MgO/Gd2Zr2O7/Hastelloy C276TM substrates by the metal organic deposition process using trifluoroacetates. Both microstructural and analytical characterizations were performed by transmission electron microscopy with selected area electron diffraction method and energy dispersive X-ray spectroscopy. The thickness of Y1−xGdxBa2Cu3O7−y with BaZrO3 film was found approximately 700nm and the film was composed of c-axis oriented Y1−xGdxBa2Cu3O7−y grains. Several types of particles, (Y,Gd)2Cu2O5, CuO and BaZrO3, were formed within the Y1−xGdxBa2Cu3O7−y film, whose sizes were about 100–200nm for (Y,Gd)2Cu2O5 and CuO particles, and about 10–20nm for BaZrO3 particles, respectively. In the Y1−xGdxBa2Cu3O7−y film, (Y,Gd)2Cu2O5 and CuO particles were dispersed heterogeneously, whereas BaZrO3 nanoparticles were found dispersed homogeneously with random orientation. In addition, electron tomographic observation was carried out to attain the three-dimensional information of polyhedral BaZrO3 nanoparticles.

Effect of cation non-stoichiometry and crystallinity on the ionic conductivity of atomic layer deposited Y:BaZrO3 films

The effects of A-site non-stoichiometry and crystallinity on the proton conductivity of anhydrous proton conducting yttria-doped barium zirconate (BYZ) thin film were investigated. The membranes were fabricated by atomic layer deposition (ALD) as it allows tailoring and varying the concentration of barium. Electrochemical impedance spectroscopy was conducted to investigate the ionic conductivity according to the stoichiometry and crystallinity of the ALD BYZ thin films.

Optimization of a fluorine-free metal-organic deposition to fabricate BaZrO3-doped YBa2Cu3O7−δ film on RABiTS substrates

In this study, we used a systematic route to optimize the fluorine-free MOD process to achieve a high critical current density (Jc) in BaZrO3 (BZO)-doped YBCO films on RABiTS substrates. The BZO content is given by 1 YBCO+x BZO films, where x is moles of BZO per 1 mole of YBCO. We found x = 0.10 to be the optimal BZO content and ∼795–805 °C to be the optimal growth temperature window with 60–90 min processing time. TEM studies show the BZO nanoparticles are ∼20 nm in size and spaced ∼50–100 nm apart. The in-field Jc and the peak pinning force (Fp) of the film grown at the optimal conditions were greatly increased at 77 K relative to pure YBCO films, achieving ∼6.7 GN m−3 at 77 K, H ‖ c in a ∼800 nm thick x = 0.10 film. The angular dependence of in-field Jc measurements also shows greatly reduced angular anisotropy at 1 and 4 T at 77 K due to isotropic pinning by BZO nanoparticles.

Effects of the vortex line shape on the critical current density in high Tc superconducting film with nanorod pinning centers

We studied the critical current density distribution in a coated conductor comprised of (Gd,Y)1Ba2Cu3O7−δ–BaZrO3 film. Transmission electron microscopy measurements showed that nanorod pinning centers tilt by ∼13° from the c-axis. Magneto-optical image (MOI) measurements showed interesting asymmetric distributions of magnetic flux density. From MOIs we calculated the asymmetric distributions of the critical current density, which is associated with the properties of vortex pinning. We were able to explain these results through the geometrical relationship of the tilted rod pinning centers and the curved vortex lines.

Fabrication of buffer layers by metal-organic deposition using 2-ethylhexanates

The fabrication of BaZrO3 (BZO) and La2Zr2O7 (LZO) films was investigated using metal-organic deposition with 2-ethylhexanates on substrates of LaAlO3(100) (LAO) single crystals and Ni-electroplated cube-textured Cu tapes. BZO and LZO films were grown epitaxially on LAO at temperatures above 600 and 750 °C in air, respectively. The BZO and LZO films on LAO had smooth surfaces with root mean square roughness of 1.4 and 0.4 nm, respectively. In contrast, BZO and LZO films fired on Ni/Cu substrates had polycrystalline structures with grain sizes of 10–20 nm.

Flux pinning properties and microstructure of SmBa2Cu3Oy thin films with systematically controlled BaZrO3 nanorods

We report a way of tuning the flux pinning properties by controlling the size and number density of BaZrO3 (BZO) nanorods without much degradation of the superconducting properties. The BZO nanorods in REBa2Cu3Oy superconducting films are known as promising c-axis-correlated pinning centers. We fabricated SmBa2Cu3Oy (SmBCO) films with BZO nanorods by a low-temperature growth technique (LTG-SmBCO+BZO films). With decreasing substrate temperature of the upper layer Tsupper in LTG-SmBCO+BZO films, the diameter of BZO nanorods decreased and their number density increased, leading to a high matching field Bϕ. Also, the considerable upturn shifts in the irreversibility field line and plateau regions in the magnetic field dependence of critical current density Jc were observed in the range from Bϕ/3 to Bϕ. These results indicate that a Bose-glass-like state of vortices localized on BZO nanorods emerges, after overcoming the vortex glass state of vortices, which are frozen on inherent pointlike disorders within the films in this magnetic field range. With this technique, it is possible to tune the flux pinning properties.

Flux Pinning Properties and Microstructure in ${\rm Sm}_{1+x}{\rm Ba}_{2-x}{\rm Cu}_{3}{\rm O}_{y}$ Films With ${\rm BaZrO}_{3}$ Nanorods Fabricated by Vapor-Liquid-Solid Growth Technique

For an improvement of Jc under applied magnetic fields, an addition of BaZrO3 (BZO) nanorods into REBa2Cu3Oy(REBCO) films is actively discussed. However, the growth mechanisms of the BZO nanorods are still evidently unexplained. In this study, in order to control the growth of BZO nanorods in REBCO films, we fabricated the Sm1+xBa2-xCu3Oy (SmBCO) films containing BZO by conventional pulsed laser deposition (PLD-Sm+BZO) and vapor-liquid-solid technique (VLS-Sm+BZO). The self field Jc's of PLD- and VLS-Sm+BZO films showed 1.3 MA/cm2 and 1.2 MA/cm2, respectively. However, magnetic field dependence of the Jc for the VLS-Sm+BZO film was twice as high as that of the PLD-Sm+BZO film at 77 K, B = 5 T. From a microstructure analysis, we found the BZO nanorods in VLS-Sm+BZO film grew nearly straight along the c-axis of the SmBCO.

${\rm GdBa}_{2}{\rm Cu}_{3}{\rm O}_{7-\delta}$ Coated Conductor on ${\rm BaZrO}_{3}$-Buffered IBAD-MgO Template

We report a successful fabrication of GdBa2Cu3O7-delta (GdBCO) coated conductor on the ion-beam assisted deposition (IBAD) MgO template with a new buffer layer of BaZrO3 (BZO). The BZO films were deposited on the IBAD-MgO template at various substrate temperatures (T S) and oxygen partial pressures (PO2) by pulsed laser deposition (PLD). In the broad ranges of T S and PO2, all BZO layers showed almost uniform in-plane texture (Deltaphi of ~ 6deg ), implying that BZO is an attractive buffer layer. The surface roughness of BZO layer was sensitive to PO2 but not to T S. On the optimally processed BZO buffer layer with 5.1 nm RMS roughness, GdBCO coated conductor deposited at T S of 750degC and PO2 of 400 mTorr exhibited Deltaphi of 4.4deg , T c,zero of 90.3 K, and J c of 1.35 MA/cm2 (77 K, self-field).

Development of In-Plume Pulsed Laser Deposition of High-Ic GdBCO Films for Coated Conductors

We studied a feasibility of pulsed laser deposition technique (PLD) for high-rate deposition of high-Ic GdBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> based films (GdBCO) with improved flux pinning characteristics. It was found that in-plume deposition (IP-PLD) of off-stoichiometric Ba-poor films at a high laser energy density combined with addition of BaZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BZO) is very helpful for suppression of critical current density (Jc) degradation vs film thickness. Very high Ic at 77.5 K in a range of 700-1000 A/cm was estimated in a self-field for short GdBCO samples deposited on Hastelloy/Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> /CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> substrates. The record high Ic of 135 A/cm in the magnetic field of 3 Tesla applied perpendicular to the film surface and minimal value of 100 A/cm in angular dependent I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> measurements were achieved on single-layer 5 microns thick GdBCO+BZO film.

Dielectric constant and leakage of BaZrO3 films

Dielectric properties of thin (&amp;lt;30 nm) BaZrO3 perovskite layers deposited onto TiN were investigated. Polycrystalline films show a dielectric constant of ∼40 and an optical band gap of ∼5.4 eV. Leakage currents of the polycrystalline BaZrO3 films are significantly higher than that of the corresponding amorphous layers. As evidenced by conductive atomic force microscopy, secondary ion mass spectrometry, and ab initio calculations, these currents may be due to hot spots and point defects related to Ti contamination of the dielectrics.

Flux-pinning Properties and Microstructure in SmBa2Cu3Oy Thin Films with BaZrO3 Nanorods

Self-organized BaZrO3 (BZO) nanorods in REBa2Cu3Oy superconducting films are known as promising artificial pinning centers. Previously, we have reported high-Jc Sm1+xBa2-xCu3Oy (SmBCO) films fabricated by a low-temperature growth (LTG) technique. The LTG technique expands the range of the deposition temperature in which the REBCO films show c-axis orientation, and makes it possible to control the crystal grain size and number density. In this study, in order to tune the pinning properties, we fabricated SmBCO films with BZO nanorods (LTG-SmBCO + BZO films) using the LTG technique and investigated the influence of the LTG technique on the growth of BZO nanorods and pinning properties in SmBCO films. With decreasing deposition temperature of the upper layer in the LTG-SmBCO + BZO films, the diameter of the films was decreased and the number density of BZO nanorods was increased, producing a high matching field, Bφ. Additionally, remarkable upturn shifts in the irreversibility field line and plateau regions in the magnetic-field dependence of Jc were observed in the range of Bφ/3 B Bφ. These results indicate that the nature of the Bose-glass-like state of vortices localized on c-axis-correlated pinning centers emerges in the range of Bφ/3 B Bφ.

Strong enhancement of flux pinning in thick NdBa2Cu3O7-δ films grown on ion-beam assisted deposition-MgO templates via three-dimensional self-assembled stacks of BaZrO3 nanodots

Thick, epitaxial NdBa2Cu3O7-δ (NdBCO) films (up to 2.1 μm) with a high density of nanoscale columnar defects parallel to the c-axis of the film were deposited on ion-beam assisted deposition-MgO templates via pulsed laser deposition. The columnar defects were composed of self-assembled BaZrO3 (BZO) nanodots. A significant enhancement in Jc for H∥c is found for these films. In addition, an overall improvement in the in-field Jc at all field orientations is observed. Compared to pure NdBCO of similar thickness, the in-field Jc at H∥c for 0.7 μm thick NdBCO+BZO film is improved by a factor of 2–4 in the field range of 0.1–4 T and 10–20 at 7–8 T at 77 K. In addition, a smaller α∼0.17 is found in the field regime where Jc∼H−α. Also, a higher maximum pinning force, Fpmax∼14 GN∕m3, is found at 3 T and a larger Hirr over 8 T is found for the NdBCO films with columnar defects.

Growth and Characterization of BaZrO&lt;sub&gt;3&lt;/sub&gt; Buffer Layer for Textured YBCO Thin Films Growth on MgO (00l) Substrate

Superconducting YBa2Cu3O7-δ(YBCO) films were grown on MgO single crystalline substrates using a BaZrO3 (BZO) buffer layer deposited by a pulsed laser deposition (PLD). Deposition condition has been optimized to obtain good epitaxial BZO film followed by deposition of YBCO superconducting films. The crystallinity and microstructure of epitaxial YBCO/ BZO/ MgO (00l) films were investigated by a two-dimensional x-ray diffraction and a field emission scanning electron microscope. The in-plane (φ-scan) measurements for the BZO films (200 ~ 500 nm thick) grown on MgO substrates revealed a narrow full width half maximum (0φ = 2o). The XRD results exhibited that YBCO films with a BZO buffer layer were well oriented in the [00l] direction perpendicular to the substrate surface. The BZO films also showed homogeneous and dense surface morphologies. By the deposition of a subsequent BZO buffer layer, YBCO was grown epitaxially on MgO with results showing a critical current density (Jc) of ~ 3.3 × 106 A/cm2 and a critical temperature (Tc) of 86 K.

Crystal Growth and Interfacial Characterization of Dielectric BaZrO3 Thin Films on Si Substrates

The growth of single crystalline oxides on silicon substrates still remains a subject of significant technological interest, since fruitful achievements can be expected by their use in various silicon device technologies. We have examined the possibility of the epitaxial growth of BaZrO3 films on Si(001) substrates by pulsed laser beam deposition. It was found that the 3-ML-thick Ba-rich Ba–Zr–O layer could act as an excellent buffer layer leading to epitaxial growth of the subsequently deposited stoichiometric BaZrO3 layer. We succeeded in obtaining the heteroepitaxially grown BaZrO3 films on Si(001) substrates.

Preparation of BaTiO3–BaZrO3 Films by Metal-Organic Chemical Vapor Deposition

Barium titanate zirconate (Ba(Ti1-xZrx)O3) films in the range of x=0 to 1.0 were prepared on (100)Pt/(100)MgO substrates at 973 K by metalorganic chemical vapor deposition (MOCVD). The effects of zirconium content (x) on the microstructure and dielectric properties of films were investigated. At x≤0.15, the Ba(Ti1-xZrx)O3 films showed highly crystallized and significant (001) orientation. The (001) orientation of the films decreased with increasing x, and the orientation became random at x>0.36. The dielectric constant of Ba(Ti1-xZrx)O3 films changed with x from 35 to 689 and showed a maximum at x=0.15. The remanent polarization (2Pr) and the coercive field (2EC) of Ba(Ti0.85Zr0.15)O3 film were 3 µC·cm-2 and 14 kV·cm-1, respectively. The onset electric field for nonohmic conduction of Ba(Ti1-xZrx)O3 film increased from 10 k to 1 MV·cm-1 with increasing x.