Ba Substitution Research Articles

Effect of Partial Ba Substitutions on the Crystallization of Sr2TiSi2O8 (STS) Glass-Ceramics and on the Generation of a SAW Signal at High Temperatures.

Because of their characteristics, including a d33 of 10–15 pC/N and high stability up to temperatures over 1000 °C, polar glass–ceramics containing fresnoite crystals can be regarded as highly effective materials for applications requiring piezoelectricity at high temperatures. In the present paper we investigate barium substitutions in an Sr-fresnoite (STS) glass–ceramic. Two aspects are studied: first, the effect of the substitution on the preferential orientation of the crystallization, and second, the ability of the glass–ceramics to generate and propagate surface acoustic waves (SAW) at high temperatures. XRD analyses show that a 10 at.% substitution of Ba allows us to keep a strong preferential orientation of the (00l) planes of the fresnoite crystals down to more than 1 mm below the surfaces. Higher substitution levels (25 and 50 at.%), induce a non-oriented volume crystallization mechanism that competes with the surface mechanism. SAW devices were fabricated from glass–ceramic substrates with 0, 10 and 25 at.% Ba substitutions. Temperature testing reveals the high stability of the frequency and delay for all of these devices. The glass–ceramic with a 10 at.% Ba substitution gives the strongest amplitude of the SAW signal. This is attributed to the high (00l) preferential orientation and the absence of disoriented volume crystallization.

Magnetic properties of Tb4+/Tb3+ mixed valence oxide Ba1−xLaxTbO3 (x = 0 − 0.2)

We investigated the magnetic properties of Ba1−xLaxTbO3 with x ​= ​0, 0.1, and 0.2. The parent compound BaTbO3, which has single valent Tb4+ ions, undergoes an antiferromagnetic transition at the Néel temperature TN ​= ​33 ​K. Substitution of Ba2+ with La3+ reduces Tb4+ into Tb3+ and significantly enhances the magnetization (M) below around 25 ​K. The enhancement of the M can be explained by the formation of ferrimagnetic (FIM) or ferromagnetic (FM) clusters caused by a magnetic interaction between Tb4+ and Tb3+. At x ​= ​0.2, the TN merges into the onset temperature of the formation of the FIM or FM clusters.

Spontaneous-reduction and photoluminescence tuning in singly-doped Ba5-Ca (PO4)3Cl:Eu2+/Eu3+ phosphors

Developing a feasible scheme for solid-state lighting with high-quality white light remains a significant challenge. Particularly, tunable luminescence with single-component white emission have been widely studied to improve the luminescence performance of phosphor-converted white light-emitting diodes (pc-WLEDs) phosphors. In this work, a novel spontaneous reduction phenomenon was first found in Eu-activated apatite-type Ba5(PO4)3Cl phosphors prepared by a solid-phase reaction in air. Under 362 nm excitation, the luminescence results showed that a broad blue Eu2+ emission band with a peak at 437 nm appears unexpectedly in addition to the usual sharp orange-red emission of Eu3+. The mixed-valence fact of Eu2+/Eu3+ was further confirmed by X-ray photoelectron spectra and time-resolved spectroscopy techniques. The underlying mechanism could be explained by a charge compensation model. Accordingly, the local crystal-site engineering control of the luminescence in Ba5-yCay(PO4)3Cl:Eu2+/Eu3+ had been studied in detail by the introduction of Ca2+. It is found that the Ca2+ substitution of Ba2+ will lead to new splitting peaks of Eu3+ emission and a red-shift followed by a blue-shift of Eu2+ emission respectively, which could eventually adjust the luminescence of phosphors to the proper white light region. These phenomena are mainly ascribed to the introduction of Ca2+ to the structure modification of activator coordination environment. Finally, based on the thermal quenching results indicate that the potential application of the single-doped mixed-valence phosphor system in pc-WLEDs.

Chemical looping catalytic steam gasification (CLCSG) of algae over La1-xBaxFeO3 perovskites for syngas production

Multifunctional perovskite-type oxides (ABO3) with flexible chemical tailoring characteristics and unique physical properties, are attracting an ever-increasing attention of scientists in the field of biomass chemical looping gasification process. Barium substituted lanthanum ferrite La1-xBaxFeO3 (x = 0, 0.3, 0.5, 0.7, 0.9, 1.0) with perovskite structure was used as oxygen carrier for algae chemical looping catalytic steam gasification (CLCSG) process for the first time. The effects of the Ba-substitution, mass ratio of perovskite and algae (P/A), temperature and water injection rate on the gasification performance were investigated. Results showed that the activity of LaFeO3 was dramatically improved by Ba substitution due to the formation of Fe4+/Fe3+ and oxygen vacancies. Among all the doped LaFeO3 perovskites, La0.3Ba0.7FeO3 (L3B7F) exhibited the best performance and gave highest syngas yield, carbon conversion and gasification efficiency. A maximum syngas yield of 1.00 m3/kg-Algae, carbon conversion of 98.86% and gasification efficiency of 96.71% were obtained at 900 °C with a water injection rate of 0.3 ml/min. Continuous high syngas yield and carbon conversion were observed during the cyclic redox tests.

Synthesis and Triple Conductive Properties of Ba and Fe Co-Doped Sr<sub>2</sub>TiO<sub>4</sub> Based Layered Perovskite: (Ba<i><sub>x</sub></i>Sr<sub>2-</sub><i><sub>x</sub></i>) (Ti<sub>0.9</sub>Fe<sub>0.1</sub>)O<sub>4-δ</sub> (<i>X</i>= 0.05, 0.10)

This study investigated the effects of Ba substitution on protonic conductive properties in the Fe doped Sr2TiO4 layered perovskite. We synthesized sintered samples of (BaxSr2-x)(Ti0.90Fe0.10)O4-δ (x= 0.05, 0.10) (BSTF05, BSTF10). The result of X-ray diffraction suggests that solid solute limitation of Ba is between x= 0.05 and 0.10. BSTF05 at 600 °C shows proton and oxide-ion conductivities as well as elecronic conductivity. It means that BSTF05 is a triple conductor at 600 °C under oxidation atmosphere. The proton conductivities in BSTF05 are lower than that in Ba un-doped Sr2(Ti0.9Fe0.1)O4-δ evaluated in our previous work, suggesting that the effect of the Ba substitution on proton defect generation is small. The redox reaction of Fe ions is more important for creation of proton defects in the layered perovskites.

The detailed studies of the structural and magnetic properties of hexaferrites Ba1−xSrxFe12O19 for 0.0 ≤ x ≤ 0.75

The monophase polycrystalline hexaferrites Ba1−xSrxFe12O19 for 0 ≤ x ≤ 0.75 were prepared using the sol–gel synthesis method. The average crystallite size (Dac) ranged from 47 to 50 nm with Sr doping. The crystal structure and magnetic properties have been studied using X-ray diffraction (XRD) and neutron diffraction (ND). The structure of the studied hexaferrites is described by the hexagonal symmetry of P63/mmc space group. Field-emission scanning electron microscopy (FE-SEM) revealed the heterogeneous distribution of the grain sizes, which takes the hexagonal shape. Energy-dispersive X-ray spectroscopy (EDS) showed that the element compositions agree with the used components for each prepared sample. The substitution of Ba2+ ions by Sr2+ enhances the thermal stability of these hexaferrites. The magnetic hysteresis loops for the studied hexaferrite samples were obtained at room temperature. Different magnetic parameters are given in this work. The magnetocrystalline anisotropy parameter (Keff) initially increases for x ≤ 0.5 and then decreases for (x = 0.75). According to the analysis of neutron data, the magnetic structure formed by the Fe3+ ions, is located in five non-equivalent crystallographic sites with tetrahedral (Fe3-4f1), octahedral (Fe1-2a, Fe4-4f2, and Fe5-12k), and trigonal bipyramidal (Fe2-2b) coordinations. The strontium doping BaFe12O19 (BFO) hexaferrite affects the crystal lattice parameters, bond lengths, bond angles, and ordered magnetic moments of iron. Finally, the enhancement of the thermal stability and some magnetic parameters of the studied hexaferrite samples could be important for applications.

Layer-structured triple-conducting electrocatalyst for water-splitting in protonic ceramic electrolysis cells: Conductivities vs. activity

Electron, proton and oxygen-triple-conducting materials are becoming the dominant steam electrode candidate to break the rate limit on the water-splitting reaction that throttles the performance of protonic ceramic electrolysis cells (PCECs). In this study, based on Pr2NiO4+δ Ruddlesden-Popper phase, we manipulate these conductivities by Pr-site Ba substitution to probe the correlation of each conductivity with the kinetics of the elementary reaction steps. It is found that the proton conductivity is vital to sustain an extended active surface area for faster adsorption of reactants and desorption of products. The effect of oxygen conductivity is surprisingly found insignificant in the water-splitting reaction. On the contrary, surface oxygen removal is discovered as the most rate-limiting process. The electronic conductivity is not a direct limiting factor. However, an electron transfer process between the current collector and the electrode junction could introduce extra resistance that is perceptible at a high operating temperature range. The best water-splitting activity is obtained on a proton conductivity/oxygen surface desorption capability well-balanced sample after Ba substitution. As a result, a water-splitting reaction resistance of 0.022 Ωcm2, a current density of 1.96 A/cm2 at 700 °C is achieved on Pr1.7Ba0.3NiO4+δ, one of the best performances for PCECs.

Chemical Looping Catalytic Steam Gasification (CLCSG) of Algae Over La <sub>1-X</sub>Ba <sub>x</sub>FeO <sub>3</sub> Perovskites for Syngas Production

Multifunctional perovskite-type oxides (ABO3) with flexible chemical tailoring characteristics and unique physical properties, are attracting an ever-increasing attention of scientists in the field of biomass chemical looping gasification process. Barium substituted lanthanum ferrite La1-xBaxFeO3 (x=0, 0.3, 0.5, 0.7, 0.9, 1.0) with perovskite structure was used as oxygen carrier for algae chemical looping catalytic steam gasification (CLCSG) process for the first time. The effects of the Ba-substitution, mass ratio of perovskite and algae (P/A), temperature and water injection rate on the gasification performance were investigated. Results showed that the activity of LaFeO3 was dramatically improved by Ba substitution due to the formation of Fe4+/Fe3+ and oxygen vacancies. Among all the doped LaFeO3 perovskites, La0.3Ba0.7FeO3 (L3B7F) exhibited the best performance and gave highest syngas yield, carbon conversion and gasification efficiency. A maximum syngas yield of 1.00 m3/kg‧Algae, carbon conversion of 98.86% and gasification efficiency of 96.71% were obtained at 900 oC with a water injection rate of 0.3 ml/min. Continuous high syngas yield and carbon conversion were observed during the cyclic redox tests.

Synergistic optimization of antiferroelectric ceramics with superior energy storage properties via phase structure engineering

Dielectric capacitors with high energy storage density and high efficiency exhibit potential applications in lightweight, miniaturized microelectronic devices. Here, (Pb, La)(Zr, Sn)O3 (PLZS) based ceramics with Ba substitution were selected and studied with in-situ Raman spectra and in-situ synchrotron X-ray diffraction. Results show that the room temperature phase structure consists of two coexisting antiferroelectric phases of OI and OII (O refers to orthorhombic), and between them the latter possesses lower forward phase-switching electric field (EAF) and should be the origin of FE(I). Meanwhile, Polarization-electric field (P-E) loops and Raman spectrum under variable temperature reveal optimal Ba content of 0.02. Suitable Ba substitution forms balanced coexisting structure and therefore achieves ultrahigh recoverable energy storage density (Wrec) of 12.8 J/cm3 and simultaneously high energy storage efficiency (η) of 84.2% under an electric field of 450 kV/cm. Extremely short discharge period of 51.6 ns and high Wrec support ultrahigh power density (PD) of 327 MW/cm3 and high discharge current density (Ddis) of 1815 A/cm2. Reasonable phase structure design after clarifying the relationship between structure and performance shows guiding significance, and the improved ultra-high Wrec and PD enhance the possibility of applications of antiferroelectric ceramics in pulsed power capacitor.

Magnetic and ferroelectric properties of Sr1−xBaxMnO3 from first principles

Density functional theory (DFT) calculations are used to study the magnetic and ferroelectric properties of Sr$_{1-x}$Ba$_{x}$MnO$_3$, with focus on $x=0.5$, under isotropic volume expansion/compression and biaxial strain. Our results indicate that, unexpectedly, Ba substitution alters the electronic structure in a way that, at fixed lattice parameter, notably enhances the interatomic magnetic exchange interactions. However, increasing Ba-content also causes a volume expansion which tends to weaken these interactions, leading to a net effect of weakly suppressed magnetism, as observed in experiments. The ferroelectric properties, on the other hand, are found to be less affected by changes in the electronic structure and can largely be understood in terms of the volume expansion caused by Ba-substitution. The calculated electric polarization as a function of biaxial strain in Sr$_{1-x}$Ba$_{x}$MnO$_3$ for $x=0$ and $x=0.5$, shows that the difference between the two is mainly due to differences in the magnetic order at certain strain values, accompanied by enormous magnetoelectric coupling.

Novel Dy and Sm activated BaSi2O5 phosphors: Insights into the structure, intrinsic and extrinsic luminescence, and influence of doping concentration

Pure and a series of BaSi2O5:RE3+ (RE = Dy, Sm) phosphors varying with the substitution of Ba2+ were prepared using a gel-combustion method. X-ray diffraction results confirmed that all samples exhibited an orthorhombic structure. FT-IR spectra showed that the samples consist of BaCO3, SiO2 network and the presence of OH groups. The photoluminescence spectrum of non-doped BaSi2O5 showed a broad-band emission peak at 520 nm. The analysis of photoluminescence emission and comparison of the chromaticity diagrams of BaSi2O5:Dy3+ and BaSi2O5:Sm3+ phosphors were presented, and their implications are also discussed. The optimum quenching concentrations and critical distances of Dy3+ and Sm3+ ions in the BaSi2O5 were 2mol%, 22.57 Å and 1 mol%, 28.44 Å, respectively. The investigation of concentration quenching behaviour, fluorescence decay curves, and decay time indicates that the dominant mechanism type leading to concentration quenching was governed by electric dipole-dipole interactions. The concentration dependence of intensity ratio of yellow-blue emission indicated that the emission of BaSi2O5:Dy3+ phosphors fell in the white light region tuning the blue and yellow components. BaSi2O5:Sm3+ phosphors may allow one to consider as potential orange-red-emitting phosphors.

CO2 reforming of CH4 over M(Ca, Ba, Sr)xLa1-xNiO3 perovskites used as coke resistant catalyst precursor

Methane and carbon dioxide are greenhouse gases that have been converted into synthesis gas for the production of oxygenated chemicals and hydrocarbons. In this paper, M(Ca, Ba, Sr)xLa1-xNiO3 (x = 0.0, 0.3 and 0.5) doped perovskites were successfully synthesized as catalyst precursors aiming at high catalytic activity and stability in the CO2 reforming of methane. These perovskites were characterized by X-ray diffraction (XRD), temperature programmed reduction by H2 (H2-TPR) and O2-temperature programmed oxidation (TPO). Its activity and carbon suppression were investigated in the CO2 reforming of methane. Results showed formation of perovskite structure, but La2NiO4 spinel and NiO were also detected in doped perovskites. The Ca, Ba and Sr partial substitution had evident influence on the reduction behavior of perovskites. All the doped perovskites used as catalyst precursors had better catalytic performance than LaNiO3. However, increasing the doping content decreased activity. Among doped perovskites, Ca0.3La0.7NiO3 showed better catalytic performance for the methane reforming reaction.

Excellent energy storage properties over a wide temperature range under low driving electric fields in NBT-BSN lead-free relaxor ferroelectric ceramics

To develop environment-friendly dielectric capacitors with low working electric field and wide useable temperature, in this work, we fabricate (1-x)Na0.46Bi0.54TiO3- xBaSnO3((1-x)NBT-xBSN) lead-free relaxor ferroelectric ceramics by adding BaSnO3 into Na0.46Bi0.54TiO3 matrix. BSN exhibits slim polarization-electric field (P-E) loops, small remnant polarization (Pr) and good temperature stability because of its room-temperature paraelectric characteristics, and has different cation ionic radii with Na0.46Bi0.54TiO3. Therefore, when BSN is introduced into NBT, the relaxor behavior of the (1-x)NBT-xBSN ceramics is more pronounced and the P-E loops are much slimmer. Besides, because the substitution of Ba2+ ions with higher valence for Na+ ions neutralizes the hole carriers, which are caused by the volatilization of Na2O, the resistivity and breakdown strength are improved with increasing BSN content. As a consequence, at x = 0.30, the ceramic exhibits simultaneously a large recoverable energy density (Wrec) of 1.51 J/cm3 and high energy efficiency (η) of 81.2% at a low driving electric field of 145.3 kV/cm because of the collaborative enhancement effect of the high breakdown strength and low remnant polarization. More interestingly, variations of the Wrec and the η for this kind of ceramic are respectively as small as 10% and 0.8% over a wide temperature range of 20–140 °C, demonstrating superior temperature stability. In this report, we provide a new and efficient way for designing and fabricating environment-friendly dielectric capacitors with good reliability and superior high-temperature energy storage capacity.

Photoluminescence evolutions and physical mechanism discussions of Sr1.95-(Ca/Ba) MgSi2O7:Eu2+ phosphors

Abstract With Ca and Ba substitutions for Sr, the photoluminescence evolution of Sr2MgSi2O7:0.05Eu2+ has been investigated and discussed. With spectra and crystal structure analysis, the photoluminescence intensity variation, the emission band shift, the chromaticity coordinate evolution and the thermal stability changes have been revealed. The corresponding physical mechanisms have been discussed. With Ca/Ba substitution, the emission spectra show entire red/blue shift; while the photoluminescence intensity are both quenched. The crystal structure and lattice parameter variations were refined. Based on the reflection spectra measurements, the forbidden band gap of the series of Sr1.95-x(Ca/Ba)xMgSi2O7:0.05Eu2+ phosphors were calculated. Both for Ca and Ba substitution, the forbidden band gap is elevated. The regular emission band red/blue shifts are ascribed to the increased/decreased crystal splitting of the Eu2+ 5d electron. Based on the estimation of the crystal splitting intensity and the calculation of the forbidden band gap, the Eu2+ 5d electron transition process and the Ca/Ba substitution tuning process are illustrated. The thermal stability of Sr2MgSi2O7: Eu2+ is promoted with Ca/Ba substitution. The thermal quenching mechanism of this phosphor can be confirmed to self-ionization. This work proves cation substitution is a suitable route to tune the photoluminescence property of the phosphors. The revealed physical mechanisms are in favor of understanding the tuning process of the phosphors.

Evidence of Ba-substitution induced spin-canting in the magnetic Weyl semimetalEuCd2As2

Recently EuCd$_2$As$_2$ was predicted to be a magnetic Weyl semi-metal with a lone pair of Weyl nodes generated by A-type antiferromagnetism and protected by a rotational symmetry. However, it was soon discovered that the actual magnetic structure broke the rotational symmetry and internal pressure was later suggested as a route to stabilize the desired magnetic state. In this work we test this prediction by synthesizing a series of Eu$_{1-x}$Ba$_x$Cd$_2$As$_2$ single crystals and studying their structural, magnetic and transport properties via both experimental techniques and first-principles calculations. We find that small concentrations of Ba ($\sim 3-10\% $) lead to a small out-of-plane canting of the Eu moment. However, for higher concentrations this effect is suppressed and a nearly in-plane model is recovered. Studying the transport properties we find that all compositions show evidence of an Anomalous Hall Effect dominated by the intrinsic mechanism as well as large negative magnetoresistances in the longitudinal channel. A non-monotonic evolution of the transport properties is seen across the series which correlates to the proposed canting suggesting canting may enhance the topological effects. Careful density functional theory calculations using an all-electron approach revise prior predictions finding a purely ferromagnetic ground state with in-plane moments for both the EuCd$_2$As$_2$ and Eu$_{0.5}$Ba$_{0.5}$Cd$_2$As$_2$ compounds - corroborating our experimental findings. This work suggests that Ba substitution can tune the magnetic properties in unexpected ways which correlate to changes in measures of topological properties, encouraging future work to locate the ideal Ba concentration for Eu moment canting.

Composition dependent mobility and bandgaps in (La0.05BaxSr0.95−x)SnO3 epitaxial films

Perovskite stannates ASnO3 (A = Ba, Sr) as transparent conducting oxides have recently attracted much attention due to their high electron mobility and high optical transparency. Here, we investigated experimentally and theoretically the composition-dependent structural, electrical, and optical properties of (La0.05BaxSr0.95−x)SnO3 (LBSSO, x = 0–0.95) thin films. Detailed x-ray diffraction characterization studies show that the LBSSO films were epitaxially grown on the LaAlO3(001) substrates. The out-of-plane lattice constants of the LBSSO films increase from 4.045 to 4.122 Å with incorporation of the Ba content from 0 up to 0.95 in the films. The electron mobility values of the films increase gradually from 22.2 to 34.4 cm2/V s with the increasing Ba contents. The direct/indirect optical bandgaps decrease monotonously from 4.64/4.04 to 4.05/3.40 eV upon changing the Ba content from 0 to 0.95. Density functional theory calculations indicated that the Ba substitution can reduce the electron effective mass and the bandgaps, leading to a higher carrier mobility.

Influence of Ca2+ substitution for Ba2+ on the crystal structure and microwave dielectric properties of Ba1−xCax(Mg1/3Ta2/3)O3 ceramics

The Ba1–xCax(Mg1/3Ta2/3)O3 (BCMT, 0 ≤ x ≤ 0.05) microwave dielectric ceramics were synthesized by the conventional solid-state ceramic route. In this paper, the effects of Ca2+ substituting for Ba2+ on the phase structure, microstructure, and microwave dielectric properties of Ba1–xCax(Mg1/3Ta2/3)O3 ceramics were investigated. X-ray diffraction (XRD) exhibited that the Ba1–xCax(Mg1/3Ta2/3)O3 ceramics possessed the main phase Ba(Mg1/3Ta2/3)O3 (BMT) when 0 ≤ x ≤ 0.05 and secondary phase Ba0.5TaO3 for x = 0.05. SEM micrographs showed that the substitution of Ca2+ for Ba2+ could increase the grain size. The apparent density was influenced by the concentration of liquid phases caused by the substitution of Ca2+ for Ba2+ ions. The microwave dielectric properties depended heavily on apparent density, B-site cation ordering degree, Ba-deficient, secondary phase and distortion of oxygen octahedral. Finally, Ba1–xCax(Mg1/3Ta2/3)O3 (x = 0.04) ceramics sintered at 1450 °C for 8 h showed superior microwave dielectric properties of er = 24.1, Q × f = 165,800 GHz and τf = 0.12 ppm/℃.

Structural and Morphological La<sub>0.85-x</sub>Ba<sub>x</sub>Na<sub>0.15</sub>MnO<sub>3</sub> (x = 0, 0.05, 0.10 and 0.15) Perovskite Manganite

Bulk polycrystalline samples La0.85-xBaxNa0.15MnO3 (x = 0, 0.05, 0.10 and 0.15) manganites were synthesized by the sol-gel route. The effect of Barium (Ba) existence on the structural and morphological was investigated by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). The structural parameters were obtained using Rietveld refinement of the XRD pattern. It was revealed the structures of compounds have rhombohedral with R-3c space group without any impurities phase. Furthermore, several changes are found to exist due to Ba substitution such as the lattice parameter, unit cells volume, average crystallite size, average Mn-O bond length (<Mn – O>) and average Mn-O-Mn bond angle (<Mn – O – Mn>). The changes in <Mn – O> and <Mn – O – Mn> due to Ba substitution, affects the double exchange interaction of the samples. SEM images reveal the existence of Ba also affects the morphology of the studied samples, which consisted of polygonal grains with homogeneous chemical composition.

Ba doping induced modifications in the structural, morphological and dielectric properties of double perovskite La2NiMnO6 ceramics

We report the modifications in the structural, morphological and dielectric properties of La2NiMnO6 (LNMO) by doping Ba at La site for three different proportions. These ceramics were successfully synthesized by the solid-state route as revealed by the X-ray diffraction patterns of three compositions. The sample phases were confirmed by the Rietveld refinement which showed monoclinic symmetry having P21/n space group. The scanning electron microscopy imaging of the pristine LNMO sample reveals ablated spheres, and this gets modified to sugar-cube like structures after the Ba substitution at La site. In addition to modification in morphology, a decrease in porosity is also noticed after Ba doping as calculated from the ratio of pore-pixels to the entire pixel-count of the image which reveals the percent porosity. The substitution of Ba2+ in place of La3+ is expected to bring about changes in the overall conduction mechanisms and also the dielectric relaxations in the LNMO. The temperature-dependent (100K–400K) and frequency-dependent (1 ​kHz–2 ​MHz) dielectric studies reveal that the Ba doping results in the decrease of dielectric constant and dielectric loss. This decrease is attributed to conversion between Ni2+ to Ni3+ and Mn4+ to Mn3+ due to Ba doping resulting in an increase of grain resistance as such decreasing possibility of most of the electrons to reach grain boundaries, which in turn causes a decrease in polarization and thus resulting in the decrement in the value of dielectric constant. Low dielectric materials are preferable and more reliable as they cause low heat dissipation and reduce any parasitic capacitance, thus allowing faster switching speeds in the fabricated devices.

Enhanced ferroelectric and ferromagnetic properties of BiFeO3‐PbTiO3 multiferroic solid solutions with Ba substitutions

AbstractDense 0.6(Bi0.9La0.1)(Ga0.05Fe0.95)O3‐0.4(Pb1‐xBax)TiO3 (BLGF‐PBT, x = 0, 0.1, 0.2, 0.3, and 0.4) ceramics with different Ba contents were prepared by the solid‐state reaction method, and effects of Ba contents on the structure and multiferroic properties were investigated. X‐ray diffraction results indicate that the Ba‐modified BLGF‐PBT ceramics exhibit single perovskite structure without detectable secondary phases, and a transition from tetragonal phase to rhombohedral one takes place with the increase of Ba content. The piezoelectric constant d33, remanent polarization Pr, and remanent magnetization Mr are improved by the Ba substitution simultaneously. Values of Pr, Mr, and d33 of BLGF‐PBT ceramics for the composition of x = 0.3 with the coexistence of tetragonal and rhombohedral phases are 20 μC/cm2, 0.05 emu/g, and 256 pC/N, respectively, much higher than those without Ba modification. The significantly improved d33 and Mr indicate that BLGF‐PBT ceramics with Ba modification provide alternative materials for multifunctional devices.