Ba Zr0 Research Articles

Development of Ba–Zr–O-Doped Y–Gd–Ba–Cu–O Coated Conductors Using a Reel-to-Reel System Furnace

Development of Ba–Zr–O-Doped Y–Gd–Ba–Cu–O Coated Conductors Using a Reel-to-Reel System Furnace

A First-Principles Thermodynamic Model for the Ba–Zr–S System in Equilibrium with Sulfur Vapor

A First-Principles Thermodynamic Model for the Ba–Zr–S System in Equilibrium with Sulfur Vapor

High‐Temperature Equilibrium of 3D and 2D Chalcogenide Perovskites

Chalcogenide perovskites have been recently proposed as novel absorber materials for photovoltaic applications. BaZrS3, the most investigated compound of this family, shows a high absorption coefficient, a bandgap of around 1.8 eV, and excellent stability. In addition to the 3D perovskite BaZrS3, the Ba–Zr–S compositional space contains various 2D Ruddlesden–Popper phases Ban + 1ZrnS3n + 1 (with n = 1, 2, 3) which have recently been reported. Herein, it is shown that at high temperature the Gibbs free energies of 3D and 2D perovskites are very close, suggesting that 2D phases can be easily formed at high temperatures. The product of the BaS and ZrS2 solid‐state reaction, in different stoichiometric conditions, presents a mixture of BaZrS3 and Ba4Zr3S10. To carefully resolve the composition, X‐ray diffraction, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy analysis are complemented with Raman spectroscopy. For this purpose, the phonon dispersions, and the consequent Raman spectra, are calculated for the 3D and 2D chalcogenide perovskites, as well as for the binary precursors. This thorough characterization demonstrates the thermodynamic limitations and experimental difficulties in forming phase‐pure chalcogenide perovskites through solid‐state synthesis and the importance of using multiple techniques to soundly resolve the composition of these materials.

Solid‐state synthesis of BaCe0.16Y0.04Fe0.8O3‐δ cathode for protonic ceramic fuel cells

AbstractProtonic ceramic fuel cells (PCFCs) are energy conversion devices based on proton conducting oxide electrolytes, which efficiently convert the chemical energy of fuel into electrical energy during operation. Since the conduction of protons has a lower activation energy than the conduction of oxygen ions, PCFCs can work at medium to low temperatures. In order to obtain better output performance at medium to low temperatures, the cathode of PCFCs needs to have better activity, and the triple (H+/O2−/e−) conducting oxide is a very good choice. In this study, the triple conducting BaCe0.16Y0.04Fe0.8O3‐δ (BCYF) cathode material was synthesized by the traditional solid‐state reaction method, and the structure and morphology of the cathode material during the synthesis process were investigated. The results show that the powder synthesized by the solid‐state reaction method has a particle size comparable with that of the wet chemical method, and the as‐fabricated electrode exhibits a polarization resistance of 0.91 Ω cm2 at 700°C on the Ba Zr0.1Ce0.7Y0.1Yb0.1O3‐δ (BZCYYb) electrolyte of 0.91 Ω cm2 at 700°C. A fuel cell, using Ni‐BZCYYb anode, BZCYYb electrolyte, and BCYF cathode, achieves a maximum power density of 213 mW cm−2 at 600°C.

Ba3Zr2Cu4S9: the first quaternary phase of the Ba–Zr–Cu–S system

Single crystals of a new semiconducting layered quaternary sulfide, Ba3Zr2Cu4S9, are synthesized by the elemental reactions at high temperatures. This phase is the first member of the Ba–Zr–Cu–S system and represents an unprecedented structure type.

Reaction mechanism on the formation of (Sr, Ba)TiO3 and Ba(Zr, Ti)O3 at near room temperature by using A(OH)2•8H2O (A = Sr, Ba) and BO2•nH2O gel (B = Zr, Ti, Zr0.45Ti0.55)

ABSTRACT Recently, our group synthesized perovskite-type oxide ABO3 (A = Sr, Ba; B = Ti, Zr) with high crystallinity simply by leaving a powder mixture of A(OH)2•nH2O and BO2 hydrous gel at room temperature to 323 K for 3–10 days. In this study, perovskite solid solution (Ba, Sr)TiO3 and Ba(Zr, Ti)O3 were synthesized to investigate the reaction mechanism in this synthesis method in detail. The perovskite solid solution (Ba, Sr)TiO3 was obtained by using barium hydroxide, strontium hydroxide and TiO2 hydrous gel as the staring materials. On the other hand, in the case of using barium hydroxide and the mixture of TiO2 hydrous gel and ZrO2 hydrous gel as the starting materials, a mixed phase of BaTiO3 and BaZrO3 was obtained. B-site-substituted perovskite solid solution Ba(Zr0.45Ti0.55)O3 was obtained by using barium hydroxide and (Zr0.45Ti0.55)O2 hydrous gel as the starting materials. From the above, it was clarified that in this synthetic method, the Sr and Ba ions diffuse into the water part of hydrous gel and then slowly react with Ti(OH)4 to form a perovskite lattice.

Petrographic and Sr–Nd–Pb–Li isotope characteristics of a complex lamproite intrusion from the Saxo-Thuringian Zone: A unique example of peralkaline mantle-derived melt differentiation

Variscan orogenic lamproites in the Bohemian Massif predominantly occur as 1 to 2 m wide and petrographically uniform dykes along the eastern borders of the Moldanubian and Saxo-Thuringian zones. Variscan orogenic lamproites were derived by preferential melting of subduction-related olivine-free metasomatic vein assemblages stabilised in the lithospheric mantle. These lamproitic melts may subsequently undergo extensive differentiation. In this study, we present the first combined petrographic and Sr–Nd–Pb–Li isotope characteristics of a complex lamproite exposed at ca 100 m long profile near Horní Rokytnice (Czech Republic) in the Saxo-Thuringian Zone. This lamproite is characterised by the primary mineral assemblage of K-amphibole + K-feldspar ± aegirine and quartz that petrographically varies from relatively primitive (fine-grained, mafic) to more differentiated (medium- to coarse-grained, felsic) pegmatitic lamproite domains. These domains may represent the product of crystallisation of immiscible liquids that had separated from the mafic melt. The primitive lamproite zone is characterised by the typomorphic minerals – baotite, benitoite, and henrymeyerite. The more differentiated pegmatitic domains are free of aegirine and show replacement of primary red-luminescent (Fe3+-rich) K-feldspar by blue-luminescent (Fe-poor) K-feldspar. Residual fluids rich in Ca, Ti, and HFSE in combination with the decreasing peralkalinity of the lamproite system resulted in the local formation of secondary zircon, titanite and quartz at the expense of the primary Ti–Ba–Zr–K lamproitic mineral assemblages. Lamproites from the Moldanubian and Saxo-Thuringian zones fall on separate mixing trends in the 87Sr/86Sr(t) - εNd(t) diagram, which indicates that the mantle beneath these two zones had been metasomatised by different crustal material. The scatter in the peralkalinity index vs. δ7Li diagram indicates that the Li isotope composition is not controlled by mixing of two end members metasome and ambient depleted mantle alone, but may also be affected by late-stage magmatic and hydrothermal processes. The compositionally zoned Horní Rokytnice dyke is special as the petrographically different types show a variation of about 4 δ-units in δ7Li due to dyke-internal processes, such as fractionation, which increases δ7Li in late-stage lamproitic melts, and post-emplacement interaction with fluids that reduced δ7Li in samples that have lost Li. Post-emplacement alteration also led to the disturbance in the Pb isotope systematics of the differentiated orogenic lamproite as indicated by variable over-correction of in situ radiogenic Pb ingrowth.

Significantly suppressed leakage current and reduced band gap of BiFeO3 through Ba–Zr Co-Substitution: Structural, optical, electrical and magnetic study

Bismuth Ferrite (BFO), Ba substituted BFO (BBFO) and Ba–Zr co-substituted BFO (BBFZO) nanoparticles have been synthesized via citrate-gel route. The common problem of BFO i.e; compositional instability, low magnetization and high leakage current was resolved by this doping technique. Remanent magnetization and remanent polarization improved significantly for BBFZO sample compared to that of BFO. Structural, optical and improved dielectric properties were also investigated. Structural study confirmed the enhanced structural distortion in BFO due to doping of Ba and Ba–Zr ions. The calculated energy band gap has been reduced to 1.52 eV for BBFZO nanoparticles from a value of 2.55 eV for BFO. Leakage current was suppressed by almost seven orders of magnitude for Ba–Zr co-substituted bulk BFO compared to that of undoped BFO. Morphological study of bulk samples has shown gradual reduction in grain size upon Ba doping and Ba–Zr co-doping in BFO, respectively.

Electro-caloric effects in the BaTiO3-based solid solution ceramics

Electro-caloric effect (ECE) was investigated in BaTiO3 (BT)-based solid solution ceramics, Ba(Zr,Ti)O3 (BZT), Ba(Sn,Ti)O3 (BST) and (Ba,Ca)(Zr,Ti)O3 (BCZT) with the composition near an invariant critical point (ICP). The samples were fabricated by the solid-state reaction method and the ECE was obtained by an indirect measurement. The 12BZ–88BT, 9BS–91BT, and 32BCT–68BZT samples showed the best polarization–electric field (P–E) hysteresis characteristics at room temperature and displayed dielectric peaks at 46, 58, and 66 °C, which are the Curie temperatures. With increasing temperature, the P–E loops changed from typical ferroelectric square shapes to paraelectric slanted shapes in the BT-based solid solution ceramics. The adiabatic temperature change due to the ECE (ΔTECE) showed the maximum values of 0.46 °C at 80 °C, 0.5 °C at 65 °C, and 0.47 °C at 75 °C, respectively, in the 12BZ–88BT, 9BS–91BT, and 32BCT–68BZT samples. The BT-based solid solution ceramics showed smaller maximum ΔTECE, but broader ΔTECE peaks at nearer room temperature than the BT ceramic. The enhancement of the ECE due to the multi-phase coexistence was not observed in BT-based solid solutions with the compositions near an invariant critical point (ICP) at which several phases coexist.

Manipulating leakage behavior via thickness in epitaxial BaZr0.35Ti0.65O3 thin film capacitors

High quality, epitaxial Ba(Zr0.35Ti0.65)O3 thin films were fabricated via radio frequency magnetron sputtering technique. The leakage current density vs electric field (J–E) tests were conducted using the device structures with Pt top electrodes and Nb-doped SrTiO3 bottom electrodes. The conduction mechanism of the films and the J–E characteristic that changed from the asymmetric structure to the relative symmetric structure were investigated. Analysis of the thin film leakage behavior suggests that, at low electric field, the conduction mechanisms are mainly bulk-limited Ohmic and space-charge-limited current. When the electric field is higher, the interface-limited Schottky emission and the Fowler–Nordheim (FN) tunneling as the dominant conduction mechanism occur for the films with a thickness below 166 nm and only FN tunneling for the films with the thickness of 300 and 400 nm. In addition, the asymmetric structure is strongly dependent on the large relative value of the Schottky barrier height between the positive and negative biases. Moreover, increasing the electric field range used to generate the bulk-limited conduction behavior and decreasing the current density induced by the interface-limited conduction through increasing the film thickness are beneficial for the films to obtain a high breakdown strength and a large energy storage density, as well as excellent efficiency.

Frequency dependent energy storage and dielectric performance of Ba–Zr Co-doped BiFeO3 loaded PVDF based mechanical energy harvesters: effect of corona poling

Bi0.95Ba0.05Fe0.95Zr0.05O3 (BBFZO) nanoparticles were synthesized by a sol-gel technique to develop a filler material with lower leakage current and oxygen vacancies compared to the host BiFeO3. In this work, we report the enhanced dielectric, ferroelectric, energy storage and energy harvesting performance of BBFZO incorporated PVDF composites. 15 wt% BBFZO loaded PVDF (15BBFZO) exhibited improved polarity (F(EA) = 77.42%) compared to neat PVDF (F(EA) = 37.01%). At an applied field of ∼14 kV cm-1 (1 Hz), this film (15BBFZO) exhibited a maximum energy storage density of 151.18 μJ cm-3 (at 1 Hz). Upon repeated human finger tapping, an average open circuit peak to peak a.c. voltage (VOC) ∼ 20 V was obtained from 15BBFZO. A comprehensive study of frequency dependent D-E loops and an extensive study of the effect of electrical poling on the output performance of the developed composite films have been performed. An improvement of the dipolar polarization was established through a frequency dependent D-E loop study of unpoled and poled 15BBFZO and from other experiments. After poling the energy storage density and VOC of 15BBFZO were 154.66 μJ cm-3 (at 1 Hz) and ∼30 V, respectively. After rectification this output electrical signal was able to charge a 10 μF commercial capacitor up to ∼5.5 V. After poling, the energy storage efficiency (η) of 15BBFZO also improved from 52.49% to 67.85% (at 1 Hz). The frequency dependence of the storage efficiency for all the samples has also been extensively investigated here. At 1 kHz, η improved to 93.30% for poled 15BBFZO.

Octahedron rotation evolution in 2D perovskites and its impact on optoelectronic properties: the case of Ba–Zr–S chalcogenides

Octahedron rotation as a distinctive structural feature with its impact on opto-electronic properties is systematically studied in 2D chalcogenide perovskites.

Ferroelectric ordering and energy storage capacity in lead-free Ba(Zr0.2Ti0.8)O3 nanoscale film capacitors fabricated using pulsed laser deposition technique

Dielectric thin film capacitors, storing large charge density, are useful in electric energy storing devices. Highly oriented lead-free BaZr0.20Ti0.80O3 (BZT20) thin films were grown on a conducting bottom layer La0.7Sr0.3MnO3 deposited on a MgO (100) substrate under an oxygen atmosphere using a pulsed laser deposition technique. X-ray diffraction studies indicate that BZT20 films were stabilized in a (100) oriented tetragonal phase. Microstructural studies on thin films indicate a smooth film (a roughness of ∼1.25 nm) with a thickness of around 320 nm. The structural sensitive A1(TO2) Raman band exhibits a discontinuous change across the tetragonal-cubic phase transition temperature Tc ∼ 275 K. The appearance of the broad Raman band in the cubic (Pm−3m) phase at an elevated temperature suggests the activation of symmetry forbidden Raman active bands. The temperature dependent band frequency and integrated intensity of the structural sensitive A1(TO2) band show anomaly across Tc. Temperature dependent dielectric studies (100–650 K) carried out in a wide range of frequencies 102–106 Hz on a fabricated Pt/BZT20/LSMO metal-insulator-metal capacitor suggest a broad dispersive peak of around 290 K. The polarization relaxation follows the Vogel-Fulcher relation with an activation energy of Ea = 0.047 eV and a freezing temperature of Tf = 246 K. The slim polarization P-E loops with a remanent polarization of ∼89.6 μC/cm2 and an EC value of ∼0.29 MV/cm were observed, suggesting its local ferroelectric ordering in corroboration with Raman and dielectric findings. From the P-E loop analysis, a large energy storage density of 31.9 J/cm3 and an energy storage efficiency of 56% were obtained. Our experimental results revealed that the BZT20 thin film capacitors have potential for energy storage device applications.

Effect of doping Gd2O3 on dielectric and piezoelectric properties of BaZr0.1Ti0.9O3 ceramics by sol–gel method

The effects of sintering temperature and doping amount of gadolinium ions on the microstructures and electrical properties of sol gel derived Ba (Zr0.1Ti0.9) O3 + xGd ceramics were investigated in this manuscript. XRD analysis showed that the main crystalline phase of BZT-xGd ceramic samples exhibit a perovskite structure without significantly change. The sample sintered at 1350 °C and doped with gadolinium ions of 0.5 mol% has uniform grain size and compact morphology. And the sample(1350 °C—0.5 mol%) also has a high piezoelectric charge coefficient of 131.33 pC/N, large plane electromechanical coupling coefficient of 0.22, high dielectric constant of 10504, and small dielectric loss of 0.01. The correlation of dielectric and piezoelectric properties of BZT-xGd ceramics with doping amount of Gd3+ ion has been explained by the lattice theory.

Enhanced electrical and magnetic properties in BZT/NFO multiferroic composites derived by MARH

Multiferroic materials comprising of ferroelectric (FE) and ferromagnetic (FM) composites exhibits added functionalities significant from scientific and technological standouts. But these FE/FM composites are very sensitive to processing parameters, sintering, and chemical modifications. In present work FE/FM composites (1 − x)(Ba Zr0.15, Ti0.85)O3–xNiFe2O4 (BZT–NFO) was sintered by microwave assisted radiant heating (MARH) technique, which has evolved as a hybrid sintering technique, where radiant and microwave sintering methods are coupled together, in such a way that, when conventional radiant heating is applied for sintering, simultaneously different (0%, 15%, 30% and 50%) Microwave power (Mw) percentages are applied in a precise and controlled manner. The present study dwells on the role of different Mw power applied during sintering on the structure, dielectric, ferroelectric and magnetic properties of (1 − x) (Ba Zr0.15, Ti0.85) O3–xNiFe2O4 (BZT–NFO) composites. Structural phase analysis carried out by X-ray diffraction displays Bragg peaks corresponding to both perovskite and ferrite phases. Since the compositional variation of ferrite remains as low as 1% for all the compositions, the overall crystal phase is dominated by perovskite phase which was further confirmed by room temperature Raman spectra. No intermediate phase or structural transitions were observed for all the compounds. Dielectric permittivity increases by 35% for the sample sintered with 15% Mw power, while leakage current decreases by an order of magnitude. At higher temperature, mobility due to oxygen vacancies/or defects present in the samples dominates the conduction mechanism. Magnetic hysteresis curve at room temperature suggests the soft magnetic nature exhibiting ferromagnetic behavior for all the samples. Sample sintered with 15 Mw power exhibits higher saturation magnetization (Ms).

Tunability of electronic and optical properties of the Ba–Zr–S system via dimensional reduction

Transition metal sulfide perovskites offer lower band gaps and greater tunability than oxides, along with other desirable properties for applications. Here we explore dimensional reduction as a tuning strategy using the Ruddlesden-Popper phases in the Ba-Zr-S system as a model. The three dimensional perovskite BaZrS$_3$ is a direct band semiconductor, with a band gap of 1.5 eV suitable for solar photovoltaic application. However, the three known members of the Ruddlesden-Popper series, are all indirect gap materials, and additionally have lower fundamental band gaps. This is accompanied in the case of by a band structure that is more favorable for carrier transport for oriented samples. The layered Ruddlesden-Popper compounds, show significantly anisotropic optical properties, as may be expected. The optical spectra show tails at low energy, which may complicate experimental characterization of these materials.

A Novel Multiple Interface Structure with the Segregation of Dopants in Lead‐Free Ferroelectric (K0.5Na0.5)NbO3 Thin Films

AbstractInterfaces in oxides are found to possess different properties and can be engineered for modifying local structure and properties of nearby area. In this work, it is reported that the interfaces can be formed in Ba/Zr (BZ)‐doped (K,Na)NbO3 (KNN) thin films by cycles of chemical solution deposition using same precursor solution. In the films, a novel and special cross‐sectional structure is observed with periodic distribution of Ba‐rich and Zr‐rich layers. The Ba‐rich and Zr‐rich layers exhibit different strain, lattice parameters, and crystal structure, leading to an obvious effect on the general ferroelectric properties of the KNN‐based thin films. Moreover, the self‐polarization is also observed, which can be understood to originate from the formed built‐in field by layered distribution of Ba and Zr in the KNN‐BZ thin films.

Effect of pore formers characteristics and melt infiltration parameters on microstructure and electrical properties of BaCe0.7Zr0.1Y0.2O3−δ-carbonate composite electrolyte

In the present work, Ba Zr0.1Ce0.7Y0.2O3−δ (BZCY7)-(Li/Na)2CO3 composite electrolytes fabricated by infiltration of molten carbonate phase into porous based BZCY7 electrolytes, prepared by using different types of pore formers including graphite, active carbon and starch. The effect of pore formers sizes, morphologies and their amounts, was investigated on the volume fraction of porosities, which can be created during sintering of BZCY7 electrolytes and on the morphologies of the formed porosities. The effect of created pores morphologies, sizes, their volume fractions and also infiltration's temperature and time on the degree of infiltration and electrical conductivity of the fabricated composite electrolytes were also studied. The results proved that by using 20 wt% of each type of the used pore formers, same amount of porosities in the range of 40–45 vol.% would be created during sintering of BZCY7 compound at 1400 °C for 5 h. By using pore formers more than 20 wt%, the amount of created porosities did not change or just increased a little and soon after it nearly became saturated. Optimum temperature and time for infiltration of melt carbonate phase was determined in the range of 530–570 °C for 2 h. Based on the four probe electrical conductivity measurements as a function of temperature, it was shown that for the composite electrolytes the Arrhenius conductivity curves is divided, at the melting point of carbonate phase, to two regions with two different slopes. The results also proved that at temperatures higher and lower than the melting point of carbonate phase, electrical conductivity of the composite electrolytes were higher and lower than what determined for dense BZCY7 based electrolyte, respectively. It was also shown that, the increase in electrical conductivity by increasing volume fraction of the carbonate phase from 10 to 20 vol percent was significant. Using carbonate phase more than 20 vol percent, although electrical conductivity increased but the rate of increasing in electrical conductivity decreased. The results also proved that electrical conductivity of the composite fabricated by using active carbon, as pore former, was highest.

Impedance spectroscopy study of Bi 0.5 (Na 0.74 K 0.16 Li 0.10 ) 0.5 TiO 3 -Ba(Zr 0.05 Ti 0.95 )O 3 ceramics prepared via combustion technique

Abstract Lead free (1- x )Bi 0.5 (Na 0.74 K 0.16 Li 0.10 ) 0.5 TiO 3 - x Ba(Zr 0.05 Ti 0.95 )O 3 or BNKLT-100 x BZT, 0.025 ≤ x ≤ 0.125, ceramics with single-phase perovskite structure were prepared via a combustion technique. Impedance spectroscopy was conducted over a wide temperature and frequency range in order to investigate the influences of BZT on electrical properties and conduction mechanisms. Analysis using impedance complex plane plots combined with spectroscopic plots of the imaginary component of the impedance and electric modulus revealed an electrically homogeneous microstructure with increasing BZT content. With the increase in BZT content, the resistivity increased from ~10 6 Ω-cm at x = 0.025 to ~10 7 Ω-cm at x = 0.125. The activation energy determined from an Arrhenius-type plot of conductivity was also found to increase from 0.97 eV ( x = 0.025) to 1.62 eV ( x = 0.125), which is close to half of the optical bandgap, suggesting a change in conduction mechanism towards an intrinsic electronic conduction mechanism. IS measurement under different oxygen partial pressure was also performed on selected sample. The possible defect chemistry conditions responsible for the observed electrical properties will also be discussed.

Influence of sintering temperature on structure, microstructure and piezoelectric properties of doped BZT–BCT ceramics

This work reports the influence of sintering temperature on structure, microstructure and piezoelectric properties of 0.48 Ba(Zr[Formula: see text]Ti[Formula: see text])O3–0.52 (Ba[Formula: see text]Ca[Formula: see text])TiO3(BZT–BCT) doped with ZnO nanoparticle ceramics manufactured by a conventional solid state reaction method. By increasing sintering temperature, the piezoelectric behaviors were improved and rose up to the best parameters at a sintering temperature of 1450[Formula: see text]C ([Formula: see text] pC/N and [Formula: see text]). The corresponding properties of undoped BZT–BCT ceramics were investigated as a comparison. The received results show that the sintering behavior and piezo-parameters of doped BZT–BCT samples are better than the undoped BZT–BCT samples at each sintering temperature.