Composition Ba0 Research Articles

Crystal structural, morphological and Raman spectroscopy characterizations of Ba0.97La0.02Ti1-xNb4x/5O3 (0.00 < x < 0.10) ceramics

In our present study, we have synthesized polycrystalline ceramics with the chemical composition Ba0.97La0.02Ti(1-x)Nb4x/5O3, denoted as BLTi1-xNb4x/5, where x takes on various values, including 0.00, 0.02, 0.05, 0.07, and 0.10. The materials were prepared through a molten salt method, followed by the formation of powders into pellets, and subsequent sintering at 800 °C for 24 h in the air. Through X-ray diffractometer (XRD), we confirmed that the synthesized ceramics exhibited a tetragonal perovskite structure, and they were found to be in a single phase. Surface characteristics were determined using Scanning Electron Microscopy (SEM). Raman spectroscopic investigations further verified the tetragonal perovskite structure of our materials. Additionally, this analysis revealed the successful incorporation of La3+ ions in place of Ba2+ ions within the A-site and Nb5+ ions substituting for Ti4+ ions within the B-site of the BT lattice. Notably, our study demonstrated the capability to adjust the Raman shifts of essential optical modes. While the majority of Raman shifts remained unchanged, La and Nb doping had a significant impact specifically on the A1[TO3] mode. This mode is associated with the deformation of the oxygen octahedron centered on the central Ti ion, indicating that the influence of these dopant ions primarily pertains to the B-site of the material.

Optical, electrical, and crystal structure study of BaZr0.01Ti0.99O3 ceramics modified with Gd3+ and Y3+ rare-earth ions

Ceramics with compositions Ba0.95Gd0.034Ti0.99Zr0.01O3 (BGdZT) and Ba0.95Y0.034Ti0.99Zr0.01O3 (BYZT) were prepared using the solid-state reaction method. The single tetragonal phase (space group P4mm) of BGdZT and BYZT ceramics is verified by analyzing X-ray spectra using the Rietveld method. The analysis of the tolerance factor (t) reveals an order-disorder phase transition in the tetragonal structure, resulting from the displacement of Ti4+/Zr4+ along the c-axis. A significant correlation is observed between the tolerance factor (t) and the phase transition temperature (Tc), as well as between the band gap of optical measurements and the degree of displacement of Ti4+/Zr4+ along the c-axis. The analysis of high-temperature electrical properties indicates that the conduction mechanism in both studied materials is a correlated barrier hopping (CBH) model, and electrical conductivity improves with increasing densification. The non-Debye behavior is confirmed by the curves of the M′′ vs.ƒ(Hz). The combination of M′′/M′′max and Z′′/Z′′max traces confirms the type of short-range charge carrier mobility.

Giant piezoresponse in nanoporous (Ba,Ca)(Ti,Zr)O3 thin film.

Lattice strain effects on the piezoelectric properties of crystalline ferroelectrics have been extensively studied for decades; however, the strain dependence of the piezoelectric properties at nano-level has yet to be investigated. Herein, a new overview of the super-strain of nanoporous polycrystalline ferroelectrics is reported for the first time using a nanoengineered barium calcium zirconium titanate composition (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCZT). Atomic-level investigations show that the controlled pore wall thickness contributes to highly strained lattice structures that also retain the crystal size at the optimal value (<30 nm), which is the primary contributor to high piezoelectricity. The strain field derived from geometric phase analysis at the atomic level and aberration-corrected high-resolution scanning transmission electron microscopy (STEM) yields of over 30% clearly show theoretical agreement with high piezoelectric properties. The uniqueness of this work is the simplicity of the synthesis; moreover the piezoresponse d 33 becomes giant, at around 7500 pm V-1. This response is an order of magnitude greater than that of lead zirconate titanate (PZT), which is known to be the most successful ferroelectric over the past 50 years. This concept utilizing nanoporous BCZT will be highly useful for a promising high-density electrolyte-free dielectric capacitor and generator for energy harvesting in the future.

Synthesis and piezoelectric properties of freestanding ferroelectric films based on barium strontium titanate

In this work, the membrane structures based on lead-free ferroelectric barium strontium titanate with composition Ba0.8Sr0.2TO3 (BSTO) were fabricated by a magnetron sputtering method. The formation of a single-phase Ba0.8Sr0.2TO3 with thickness of 300 nm sintered on Si substrate is confirmed by XRD analysis. It is shown that films without a silicon substrate exhibit ferroelectric and piezoelectric properties. The piezoelectric and ferroelectric behaviors of BSTO thin film without a silicon substrate were confirmed through a piezoelectric force microscopy and Kelvin probe force microscopy and measurements of the effective piezoelectric coefficients (d33 and d15). Images of the residual potential of polarized areas have been obtained on the membranes, which are stable over time despite the absence of a lower electrode. Additionally, a local of ferroelectric hysteresis loop has been observed. A combination of the structural and piezoelectric measurements reveals that it possible to create freestanding ferroelectric films based on Ba0.8Sr0.2TO3 system, establishing it as a promising candidate for high-performance electromechanical applications.

Synthesis and piezoelectric properties of freestanding ferroelectric films based on barium strontium titanate

In this work, the membrane structures based on lead-free ferroelectric barium strontium titanate with composition Ba0.8Sr0.2TO3 (BSTO) were fabricated by a magnetron sputtering method. The formation of a single-phase Ba0.8Sr0.2TO3 with thickness of 300 nm sintered on Si substrate is confirmed by XRD analysis. It is shown that films without a silicon substrate exhibit ferroelectric and piezoelectric properties. The piezoelectric and ferroelectric behaviors of BSTO thin film without a silicon substrate were confirmed through a piezoelectric force microscopy and Kelvin probe force microscopy and measurements of the effective piezoelectric coefficients (d33 and d15). Images of the residual potential of polarized areas have been obtained on the membranes, which are stable over time despite the absence of a lower electrode. Additionally, a local of ferroelectric hysteresis loop has been observed. A combination of the structural and piezoelectric measurements reveals that it possible to create freestanding ferroelectric films based on Ba0.8Sr0.2TO3 system, establishing it as a promising candidate for high-performance electromechanical applications.

BaZrO3-BaTiO3-CaTiO3 piezoceramics by a water-based mixed-oxide route: Synergetic action of attrition milling and lyophilization

This manuscript shows an innovative water-based processing route to fabricate lead-free piezoceramics. It faces the challenge of substituting conventionally used organic solvents by innocuous water. The procedure involves two methods of widespread use in industry: attrition ball-milling and freezing-lyophilization. Powders with nominal composition (Ba0.92Ca0.08)(Ti0.95Zr0.05)O3 were effectively obtained. A narrow monomodal size distribution (600 nm) proved high reactivity that allowed solid-state synthesis at ultra-low temperature (700 °C-2 h). Optimal two-step sintering method (900 °C-3 h,1280 °C-6 h) allowed well-sintered homogeneous ceramics with pure tetragonal perovskite phase. They showed high piezo-sensitivity (d33 =320 pC/N, d31 =−110 pC/N, kp =31.45% and Np =2750 kHz·mm, ε′33T=3670, tanδ=0.036 at 1 kHz), comparable to that found for routes in organic media. Therefore, attrition ball milling in water and lyophilization work in synergy to successfully activate the precursors, influencing on the structural, microstructural and electrical properties of the final BCZT ceramics. This is an unprecedented development to produce piezoelectric ceramics using a sustainable, environmentally benign water-based process, with a positive impact in noteworthy industrial applications.

Development of Tunable Ferroelectric Ceramic Capacitors.

Ferroelectric perovskite ceramics with a high dielectric constant, low loss, high tunability, and high electric breakdown are ideal for nonlinear transmission lines (NLTLs) to generate radio frequency (RF) signals at high-power levels. To achieve the required properties, a comprehensive study of the material phase transitions and the optimal ratio adjustment between the chemical elements in the perovskite crystal structure is required. The advancement of this solid-state technology is the most promising optimization for NLTLs in developing high-power (>100 MW) devices with high tunability (>60%) and high repetition rate (>1 kHz) for soliton generation. The barium strontium zirconium titanate (BSZT) ceramic compositions were synthesized and characterized to maximize material tunability. The composition Ba0.97Sr0.03Zr0.2Ti0.8O3 exhibited a high permittivity (>12200), low loss tangent (< 0.01), and an exceptional tunability of the order of 79% at an electric field of 10 kV/cm near the phase temperature transition at 300 K. Ferroelectric ceramic is an outstanding material with promising characteristics for producing RF signals in an NLTL, and here, the BSZT is considered for this application.

Study of dielectric, impedance and transport properties of co-doped Ba0.5Sr0.5TiO3 ceramics

Dielectric properties and Electrical response of BST ceramics having composition Ba0.5Sr0.5Ti0.98Sn0.01Zr0.01O3 synthesized by solid state reaction route are studied in this piece of work. The structural part analysis is done using XRD technique and scanning electron microscopy and is confirmed to be of cubic structure. Electrical characterization through impedance and modulus spectroscopy is made over a frequency region of 1 kHz to 1 MHz from ambient temperature to 400 °C. Near constant value of Ɛr and significantly low and flat loss tangent at room temperature are achieved in the material which suggest possible application in electronic circuits. Temperature dependent broadened loss peaks observed beyond 250 °C indicated thermally activated conductivity/ relaxation process in the material. Impedance spectroscopy results were examined in alternate formalism for the role of grain boundary and grain in various processes. The computed activation energy for charge carriers provides information of the transport phenomena. The estimated values suggest that oxygen vacancies play important role in conduction process. The activation energy is estimated by fitting temperature dependent relaxation time with Arrhenius equation and the type of charge carriers involved in the relaxation process are suggested. Frequency dependent ac conductivity plots at various temperatures obey Johnscher’s law. Variation of exponent in Johnsher’s power law with temperature well agrees with correlated barrier hopping (CBH) model for ac conduction mechanism.

Structural and magnetic conduct in Sm and Al substituted Ba0.9Sm0.1Fe10Al2O19 M-type hexaferrites at different sintering temperatures

The hexagonal ferrites with composition Ba0.9Sm0.1Fe10Al2O19 has been prepared by using conventional solid state reaction method. As prepared samples were then sintered at different sintering temperatures to analyze the effects on magnetic and structural properties of Barium hexa ferrites. These samples were then characterized by using various techniques. For structural characterization x-ray diffraction technique was used. XRD results confirmed phase pure hexagonal structure. No impurity peaks were observed. For Morphological analysis of all the samples Scanning Electron Microscopy (SEM) was utilized. SEM micrographs suggested the formation of hexaferrites material with homogenous distribution of particles. Magnetic properties were measured by permanent magnetic measuring system. Magnetic conduction of material was tested under varying magnetic field of ± 30 KOe at room temperature. The saturation magnetization value was observed 48.55 emu g−1 and coercivity 5.01KOe for the sample sintered at 1220 °C. As the sintering temperature rises, the values for magnetic saturation decreases to 46.24 emu g−1 and coercivity increases up to 5.26 KOe at 1270 °C.

Incorporation of rare earth elements into [formula omitted

The structural effects of the incorporation of the rare earth elements (REE) La, Ce, Pr, Nd, Eu, Sm, Gd, Er, Tm, Yb and Y into a synthetic Ba–Ca carbonate have been investigated. We precipitated solutions with a composition Ba0.9Ca1.1(CO3)2 doped with REE-nitrates. The precipitate, with few exceptions, consisted of a crystalline solid, slightly depleted in Ba with respect to the expected composition, and an amorphous phase. On heating, the whole sample became crystalline and consisted of a Ba-enriched and a Ba-depleted phase. The phases are isostructural. The lattice parameters are strongly influenced by the incorporation of ≈ 6% REE. There is a linear dependence of the unit cell volume on the radius of the incorporated REE for those elements with a radius < 1.0 Å, i.e. Yb, Tm, Er, Y, Gd, Sm, Eu, Nd and Pr, while the unit cell volume of a sample doped with La (r(La) = 1.03 Å) and Ce (r(Ce) = 1.01 Å) is not well described by this dependency. Raman spectroscopy shows that the local environment of the CO3-groups does not differ substantially between the Ba-enriched and the Ba-depleted phase, but changes linearly as a function of the ionic radius of the REE. The present study clearly shows that substantial amounts of REE can be incorporated into the Ba–Ca-carbonate studied here, making it potentially useful as a matrix in nuclear waste treatments involving aqueous nitrate solutions of lanthanides and actinides.

Influence of the upper electrode material on the electrophysical properties of MDM structures based on ferroelectric films

Ferroelectric films of the composition Ba0.8Sr0.2TiO3 (BST) were synthesized on platinized silicon substrates by RF sputtering. Top electrodes made of nickel, aluminum, copper and chromium were formed on the grown films by electron beam sputtering. The results of studies of the electrophysical properties of the obtained metal-dielectric-metal (MDM) heterostructures (Me-BST-Pt-Si) are presented. Keywords: ferroelectric BST films, metal-dielectric-metal (MDM) structures, microstructure, electrophysical properties.

Crystallographically Textured and Magnetic LaCu-Substituted Ba-Hexaferrite with Excellent Gyromagnetic Properties

Excellent gyromagnetic properties of textured, bulk Ba-hexaferrite samples are required for low-loss, self-biased applications for microwave and millimeter-wave (MMW) devices. However, conventionally processed bulk Ba-hexaferrite ceramics typically demonstrate low remanent magnetization values, 4πMr, of 2.0~3.0 kG, and relatively large ferromagnetic resonance (FMR) linewidths, ΔHFMR, of 0.8~2 kOe. These properties lead to the development of high-performance, practical devices. Herein, crystallographically textured Ba-hexaferrite samples, of the composition Ba0.8La0.2Fe11.8Cu0.2O19, having excellent functional properties, are proposed. These materials exhibit strong anisotropy fields, Ha, of ~14.6 kOe, high remanent magnetization, 4πMr, of 3.96 kGs, and a low ΔHFMR of 401 Oe at zero-bias field at the Q-band. Concomitantly, the broadband millimeter-wave transmittance was utilized to determine the complex permeability, μ*, and permittivity, ε*, of textured hexaferrites. Based on Schlöemann's theory of complex permeability, μ*, the remanent magnetization, 4πMr, anisotropy field, Ha, and effective linewidth, ΔHeff, were estimated; these values agree well with measured values.

Effect of temperature on structural and magnetic properties of Co and Mg doped M-type hexaferrites

Using the sol-gel auto combustion method, M-type barium hexaferrite of composition Ba0.6Co0.4Mg0.4Fe11.6O19 was prepared. The precursor was divided into three parts and heated at three different temperatures i.e., 9000C, 10000C, 11000C. The structural samples were investigated using an XRD analysis. The variation of crystallite size and lattice constant to temperature was studied from the XRD data. The functional groups attached to the samples were investigated using Fourier transform infrared spectroscopy. To understand the topography and elemental composition, the sample was analysed using a field emission-scanning electron microscope (FESEM). A VSM instrument was employed to investigate the magnetic property of the three samples. Magnetic parameters such as coercivity, saturation magnetization, magnetic retentivity, anisotropy constant, etc were calculated and tabulated.

Study of dielectric property, electric modulus and conduction phenomena of Sn-modified Ba0.5Sr0.5TiO3 ceramics

BST ceramics having a composition of Ba0.5Sr0.5Ti1- x Sn x O3 (x = 0.03) was prepared following a high-temperature solid state reaction route with BaCO3, SrCO3, TiO2 and SnO2 as raw materials with a suitable stoichiometric ratio. The structural configuration was confirmed by XRD study, and the analysis revealed the structure to be of cubical type. SEM analysis was carried out to get a clear picture of grain and grain boundary. Dielectric and electrical characterization were conducted as a function of temperature as well as frequency ranging from 1kHz to 1 MHz. Complex and modulus spectroscopy analysis were carried out for deep understanding of the material behavior. Broadened dielectric loss peaks were obtained beyond a temperature of 250 °C indicating a non-Debye type relaxation behavior. relaxation peaks were observed at high temperature in a modulus plot, and the activation energies were calculated. The ac conduction phenomenon was found to be thermally activated and the frequency dependence followed Johnscher’s Law. In the present study, a noticeable invariance nature of dielectric constant as well as flat and moderately low loss was observed at moderate temperatures and over a broad range of frequency making the material suitable for wide band application.

The influence of the PZT buffer layer on electrophysical properties OF MDM structures with the BST film

Films of the composition Ba0.8Sr0.2TiO3 (BST) were synthesized by the method of high-frequency (HF) sputtering on the buffer layer of a ferroelectric film of the composition PbZrxTi1-xO3 (PZT). Comparative results of electrophysical properties of three different metal--dielectric--metal (MDM)-structures are presented: Pt/BST/Ni, Pt/PZT/Ni, and Pt/PZT-BST/Ni. Keywords: metal--dielectric--metal structures, ferroelectric films of composition Ba0.8Sr0.2TiO3, a buffer layer, electrophysical properties.

A weak manifestation of the field effect in metal-dielectric-semiconductor structures with a ferroelectric insulating layer Ba-=SUB=-x-=/SUB=-Sr-=SUB=-1-x-=/SUB=-TiO-=SUB=-3-=/SUB=-

High-frequency measurements of the capacitance and conductivity of Ni-Ba0.8Sr0.2TiO_3-Pt and Ni-Ba0.8Sr0.2TiO_3-Si objects with a ferroelectric thickness of 120 nm in the paraelectric phase were carried out. It is shown that in the entire range of external voltages, the electric field practically does not penetrate Si. The conclusion made earlier about the reasons for the weak manifestation of the field effect is confirmed --- the polarization of the ferroelectric layer is almost completely shielded by the charges of electronic traps at the Ba0.8Sr0.2TiO_3-Si contact. It is noted that a sharp decrease due to passivation of the activity of surface traps will allow implementing transistors based on metal-BST-Si structures with a working surface channel of non-basic charge carriers and will ensure the construction of high-quality FeRAM non-volatile memory cells. Keywords: metal-dielectric-semiconductor-structures, metal-dielectric-metal-structures, ferroelectric films of the composition Ba0.8Sr0.2TiO3, high-frequency impedance.

The influence of the PZT buffer layer on electrophysical properties of MDM structures with the BST film

Films of the composition Ba0.8Sr0.2TiO3 (BST) were synthesized by the method of high-frequency (HF) sputtering on the buffer layer of a ferroelectric film of the composition PbZrxTi1-xO3 (PZT). Comparative results of electrophysical properties of three different metal--dielectric--metal (MDM)-structures are presented: Pt/BST/Ni, Pt/PZT/Ni, and Pt/PZT-BST/Ni. Keywords: metal--dielectric--metal structures, ferroelectric films of composition Ba0.8Sr0.2TiO3, a buffer layer, electrophysical properties.

A weak manifestation of the field effect in metal-dielectric-semiconductor structures with a ferroelectric insulating layer Ba-=SUB=-x-=/SUB=-Sr-=SUB=-1-x-=/SUB=-TiO-=SUB=-3-=/SUB=-

High-frequency measurements of the capacitance and conductivity of Ni-Ba0.8Sr0.2TiO_3-Pt and Ni-Ba0.8Sr0.2TiO_3-Si objects with a ferroelectric thickness of 120 nm in the paraelectric phase were carried out. It is shown that in the entire range of external voltages, the electric field practically does not penetrate Si. The conclusion made earlier about the reasons for the weak manifestation of the field effect is confirmed --- the polarization of the ferroelectric layer is almost completely shielded by the charges of electronic traps at the Ba0.8Sr0.2TiO_3-Si contact. It is noted that a sharp decrease due to passivation of the activity of surface traps will allow implementing transistors based on metal-BST-Si structures with a working surface channel of non-basic charge carriers and will ensure the construction of high-quality FeRAM non-volatile memory cells. Keywords: metal-dielectric-semiconductor-structures, metal-dielectric-metal-structures, ferroelectric films of the composition Ba0.8Sr0.2TiO3, high-frequency impedance.

Structural, Dielectric and Raman Spectroscopy of La3+–Ni2+–Zn2+ Substituted M‐Type Strontium Hexaferrites

AbstractIn this work, M‐type strontium nanohexaferrites with chemical composition Ba0.8−xSr0.2LaxFe12−x−yNixZnyO19 (x = 0.00, 0.05, 0.10; y = 0.00, 0.08, 0.16) are prepared using sol–gel auto‐combustion technique. The formation of single phase hexagonal ferrites is confirmed from XRD analysis. It also reveals the presence of magnetite and the crystallites sizes are in the range of 21.31–29.91nm. The lattice constants are found to decrease with an increase in cation substitution. The FTIR spectra of the sample show three dominant peaks in the range of 400–600 cm–1 which indicate the formation of the desired hexaferrite structure. The field emission scanning electron microscope images reveal large crystallites with shapes close to the hexagonal platelet‐like whose sizes are nonuniformly distributed. Also, agglomeration is observed due to magnetic interactions between the crystallites. The dielectric constant, dielectric loss, conductivity, and dielectric modulus are analyzed using the Maxwell–Wagner model. Dielectric constant is enhanced at high frequency in the entire sample and reduction of dielectric loss is also observed with further cations substitutions.

Effective dielectric properties of Cement/Ba0.06(Na0.5Bi0.5)0.94TiO3 composites: A comparative approach

Lead-free ceramic powder of a morphotropic phase boundary composition Ba0.06(Na0.5Bi0.5)0.94TiO3 (BNBT) was prepared from a solid-state synthesis route. The cement-ceramic (1−ϕ)cement/ϕBNBT; 0 ≤ ϕ 1.0 composites were fabricated. The filler concentration-dependent values of the bulk density and real part of complex permittivity showed an increasing trend of variation while the apparent porosity and imaginary part of complex permittivity followed a decreasing trend. In order to test the acceptability of dielectric mixture equations of the inclusion material in the mixture, five such equations have been chosen. The Bruggeman, and Rother-Lichtenecker equations showed their coherence with minimal deviation from the experimental results of the real part of complex permittivity for the entire measurement range of volume fractions. Also, a first-order exponential growth/decay type of mathematical model was suggested which could fit the experimental data excellently well (r2 > 0.97).