SBN Ceramics Research Articles

Tailoring Zr-doped tungsten bronze (Sr,Ba,Gd)Nb2O6 relaxor ferroelectric with high electrical insulation interface for dielectric capacitor

Tetragonal tungsten bronze structure (TTB) compounds have attracted tremendous interest for their applications in energy storage, especially as dielectric capacitor mediums. However, constrained by the inverse correlation of polarization and electric breakdown field in relaxor ferroelectrics, there is still a major challenge in improving energy density. To addresse this challenge, a viable strategy of constructing relaxor behavior with robust electrical insulation in TTB-type Sr0.485Ba0.47Gd0.03Nb2-xZrxO6 (SBN-Gd-Zrx) by introducing ZrO2 during the preparation process was proposed. By introducing Zr4+ in the B-site, we have revealed how Zr4+ affects the dielectric and ferroelectric characteristics to explore the intrinsic relaxation. Based on the analysis of Rietveld refinement against synchrotron X-ray powder diffraction and Raman results, the substitution of Gd3+ and Zr4+ for Sr2+ and Nb5+ in Sr0.53Ba0.47Nb2O6 caused a decline in tetragonality and a shrinkage of the unit cell due to the lattice defect of [GdSr]• and [ZrNb]', which mutually compensates effectively alleviate the distortion of BO6 and then favors the balance of polarization and dielectric constant. The accrual of additional ZrO2 at grain boundaries significantly enhances electrical insulation characteristics, as validated by complex impedance spectroscopy. At near room temperature, all Zr-doped SBN-Gd compounds of the series exhibit heightened relaxation and undergo a phase transition from ferroelectric to paraelectric. As a result, in tandem with the synchronous augmentation in breakdown electric field (EB) and saturation polarization (Pm), optimal energy storage characteristic is realized in the SBN-Gd-Zr0.2 sample. It attains a remarkable Wrec of 2.67 J/cm3 and an efficiency ƞ of 91.21 %, showcasing excellent suitability in terms of different frequencies and temperatures, which far exceeds that of Gd-modified SBN ceramics and pure SBN ceramics. These results exemplify an efficacious strategy for designing novel TTB dielectrics by coupling relaxor modulation with electrical insulation, and position them competitively for implementation in dielectric storage capacitors utilized in pulsed power devices.

Grain-size-insensitive dielectric properties of Sr0.6Ba0.4Nb2O6 relaxor ferroelectric ceramics with tetragonal tungsten bronze structure

The influence of grain size on the dielectric properties of Sr0.6Ba0.4Nb2O6 (SBN60) ceramics with a tetragonal tungsten bronze structure was examined. The conventional and two-step sintering procedures were used to fabricate dense and phase-pure SBN60 ceramics with grain sizes ranging from 2.2 μm to 17.3 μm. In the temperature dependence of the dielectric permittivity, all samples showed a relaxor-like broad dielectric peak with a maximum at around 60 °C. The maximum dielectric permittivity and dielectric maximum temperature of the SBN ceramics were found to be less dependent on the grain size. The reason for the grain-size-insensitive dielectric properties of the SBN60 ceramics is discussed based on the analysis of the dielectric properties and Raman spectra.

Exploring determinants of lattice structure and high energy storage properties of Fe-doped SBN ceramics

(Sr0.5Ba0.5)1+xNb2-xFexO6 (SBNF-x, 0 ≤ x ≤ 0.20) ceramics were prepared using the conventional solid-state reaction method. With the increase in x, the tungsten bonze structure of the ceramics will transform from “unfilled” to “filled.” The crystallographic parameters obtained using the Rietveld method on XRD patterns were used to explore the determinants of the lattice structure. Lattice parameter a is dominated by the distance of the A1- and A2-sites via the Coulomb interaction. The average bond length of Nb1O4 controls the change of c due to the symmetrical environment around the Nb1O6 octahedron. High energy storage properties appear in low doping samples. The discharge energy density of SBNF-0.02 is 0.595 J/cm3, with a storage efficiency of 91.3%, and of SBNF-0.04 is 0.680 J/cm3, 5.3 times the value of SBNF-0, with a storage efficiency of 83.6%. SBNF-x (0.02 ≤ x ≤ 0.04) ceramics with high discharge energy density and high storage efficiency are promising candidates for producing high energy density capacitors.

Oxygen vacancy effect on ionic conductivity and relaxation phenomenon of Sr<sub><i>x</i></sub>Ba<sub>1–<i>x</i></sub>Nb<sub>2</sub>O<sub>6</sub> ceramics

Due to the various risks caused by lead, the research of lead-free ferroelectric functional ceramics has been one of research hotspots recently. And relaxor ferroelectrics have an important position in materials for ceramic capacitor due to their low temperature change rate and large electrostrictive coefficient. However, the lead-free Sr<sub><i>x</i></sub>Ba<sub>1–<i>x</i></sub>Nb<sub>2</sub>O<sub>6</sub> ceramic is a non-filled tungsten bronze structural material whose Curie temperature can be adjusted by changing the proportion of Sr composition. The increase of Sr concentration in ceramic can cause relaxor behavior and improve dielectric constant and ferroelectric properties. In this work, Sr<sub><i>x</i></sub>Ba<sub>1–<i>x</i></sub>Nb<sub>2</sub>O<sub>6</sub> (<i>x</i> = 0.4, 0.5 and 0.6, abbreviated as SBN40, SBN50 and SBN60, respectively) ceramics are prepared by a high-temperature solid-state reaction process. The dielectric properties and the impedances of the Sr<sub><i>x</i></sub>Ba<sub>1–<i>x</i></sub>Nb<sub>2</sub>O<sub>6</sub> ceramics are investigated in detail. It is worth noting that the high-temperature diffusion for the Sr<sub><i>x</i></sub>Ba<sub>1–<i>x</i></sub>Nb<sub>2</sub>O<sub>6</sub> has not been studied before. Furthermore, the analysis of high-temperature dielectric behavior and impedance of lead-free functional ceramics is important for the application of functional ceramics in the high-temperature environment. The temperature of phase transition for SBN40, SBN50 and SBN60 are 401.15 K, 355.15 K, and 327.15 K, respectively, which are obtained from the modified Curie-Weiss law. The result shows that the increase of Sr composition leads the phase transition temperature from ferroelectric to paraelectric phase to decrease. In addition, the calculated value of diffusion phase transition parameter <i>γ</i> for SBN40, SBN50 and SBN60 are 1.53, 1.90 and 1.94, respectively, showing that it is close to an ideal relaxor ferroelectric with the Sr content increasing in SBN ceramics at low temperature. In addition, it is noticed that a similar diffusion appears in at high temperature. This phenomenon is unrelated to the phase transition, but it is corresponding to high temperature dielectric relaxation which is related to oxygen vacancy. As expected, the impedance spectroscopic data present a thermally activated relaxation phenomenon. Finally, activation energy for conduction and relaxation are calculated from the impedance and dielectric data through the Arrhenius law. Comparing the activation energy values for conduction and relaxation, it can be obviously concluded that the trap-controlled conduction process should be responsible for the relaxation process of sample. And the hopping of ions, caused by oxygen vacancies, plays a critical role in the dielectric relaxation process at high temperature.

Influence of lone pair on structural and electrical properties of Sb substituted Bismuth layered SrBi2Nb2O9 ceramics

Antimony (Sb) substituted Strontium Bismuth Niobate ceramics with chemical formula SrBi2-xSbx Nb2O9 (SBSN) have been prepared through conventional solid state reaction method with varying Sb content in the range (x = 0.0 to 0.5). Limited solubility of Sb content in SBN ceramics were revealed through X-ray diffraction studies which indicates secondary phases of Sb2O3 in prepared ceramics for Sb content x > 0.2. Formation of single phase with orthorhombic structure were confirmed for compositions having x = 0.0 to 0.2. Increase in c-axis of lattice crystal are analyzed and correlated to the ionic structure and existence of lone pair in Sb. Dielectric properties of all SBSN ceramics compositions are studied as a function of temperature over the frequency range of 100 Hz–1 MHz. Increase in Sb incorporation shows insignificant shift in Ferroelectric to Paraelectric Phase transition Temperature in SBSN ceramics. Sb substitution results in the increase in ferroelectricity (2Pr = 15.4 μC/cm2) and poiezoelectric coefficient (d33 = 20 pC/N) for composition having x = 0.1 in SBSN ceramic. Sb substitution results in increase of piezoelectric coefficients (d33) whereas piezoelectric charge coefficient values for composition SrSb0.1Bi1.9Nb2O9 was found to be comparable to that of PZT at room temperature. Existence of lone pair of electron in Antimony were correlated with high piezoelectric coefficient in SBSN ceramics.

MgO-modified Sr0.7Ba0.3Nb2O6 ceramics for energy storage applications

We explored the phase structure, microstructure, dielectric and energy storage properties of MgO-modified strontium barium niobate Sr0.7Ba0.3Nb2O6-xwt%MgO (SBNMx; x = 0–5) ceramics fabricated via conventional solid-state sintering precess. X-ray diffraction analysis indicates Mg2+ incorporates into lattice at x = 0.5 and secondary phases come into formation for samples at x ≥ 1, which results in the decrease of dielectric constant. There is also significant reduction of dielectric loss up to 0.002. Compared with pure SBN ceramics, the grain size of SBNMx ceramics becomes denser and more uniform, moreover, the dielectric breakdown strength shows increasing trend from 137 kV/cm to 226 kV/cm, which is in favor of the energy storage. SBNM0.5 ceramics presents the optimal energy storage performance: energy storage density of 0.93 J/cm3 and energy storage efficiency of 89.4% at 157 kV/cm, indicating that SBNM ceramics are prospective candidates for high voltage capacitor applications.

Substitution‐induced near phase transition with Maxwell–Wagner polarization in SrBi2(Nb1−xAx)2O9 ceramics [A = W, Mo and x = 0, 0.025

AbstractThe synthesis, micro‐structure, spectroscopic, and dielectric properties of [with AW, Mo and , 0.025] ceramics were systematically studied. A relative density of 98% was obtained for all the samples using a two‐step solid state sintering process. XRD images showed that a single phase layered perovskite structure of (SBN) was formed. The orthorhombic structure with phase group was found up to ∼2.5 at.% substitution of W and Mo into the SBN matrix. SEM revealed the rod‐like grain structure similar to the Maxwell–Wagner (MW) parallel plate capacitor model in SBN ceramic, whereas smaller heterogeneous grain structure was observed in W and Mo donor doped ceramics. The initial high value of real and imaginary part of relative permittivity also indicated the presence of interfacial MW relaxation in the SBN ceramics. The experimental data fit well to the theoretical data obtained from MW polarization model in SBN ceramics. The possible origin of the difference of the properties present in the doped sample has been explained based on grain size, orientation, and modification done in the ceramic matrices.

Synthesis and investigation of RE(III) cation substituted SBN and SBT ceramics

ABSTRACTPhysico-chemical, structural and electric properties of Aurivillius phases SrBi2-xSmxNb2O9 and SrBi2-ySmyTa2O9 with x = 0.0 and 0.4 obtained in muffle and microwave furnace have been investigated by the X-ray diffraction, DTA, FTIR-spectroscopy and dielectric spectroscopy methods. The perovskite-like structure of solid solutions obtained is characterized by the orthorhombic symmetry. The assumption about the non-statistical distribution of Sm(III) cations crystal structure of Aurivillius phases was made according to the obtained results. It has been found that Sm(III) cations introduction does not influence on TC of SrBi2-xSmxNb2O9 solid solutions.

Effect of Microwave Sintering on Electrical Properties of Sr-deficient and Bi-rich Strontium Bismuth Niobate (Sr0.8Bi2.2Nb2O9) Ferroelectric Ceramic

Nonstoichiometric strontium bismuth niobate (Sr0.8Bi2.2Nb2O9: SBN) ceramic was prepared using conventional solid-state reaction and microwave sintering methods. Complex impedance spectroscopy (CIS) has been used to investigate the intra and intergranular contribution to the impedance SBN ceramics as a function of temperature and frequency. Complex impedance Cole‑Cole plots were used to interpret the relaxation mechanism in SBN ceramic which showed a non-Debye relaxation. The grain and grain boundary contribution to conductivity have been estimated from the Cole‑Cole plots. The bulk (grain) resistance of both samples was found to decrease with rise in temperature indicating negative temperature coefficient of resistance (NTCR) type behavior like that of semiconductors. The microwave sintered SBN was found to have low value of bulk resistance indicating more increase in conductivity as compared to conventionally sintered SBN. The temperature dependence of the relaxation time was found to obey the Arrhenius law. Studies of electrical modulus show the presence of hoping conduction mechanism in SBN.

Preparation and characterization of Sr0.5Ba0.5Nb2O6 glass-ceramic on piezoelectric properties

We studied the influence of heat treatment time on the optical, thermal, electrical, and mechanical properties of strontium barium niobate (Sr1−xBaxNb2O6; hereafter SBN) piezoelectric glass-ceramics with tungsten bronze-type structure, which have good piezoelectric properties and are important lead-free piezoelectric materials. We found that the best heat treatment time is 4 h. The properties of the prepared materials are better than that of SBN ceramics and the glass-ceramic growth is faster than the SBN crystal when the heat treatment time of the SBN piezoelectric glass-ceramic is controlled, reducing the preparation costs greatly.

Structure and electric properties of cerium substituted SrBi1.8Ce0.2Nb2O9 and SrBi1.8Ce0.2Ta2O9 ceramics

SrBi1.8Ce0.2Nb2O9 (SBCN) and SrBi1.8Ce0.2Ta2O9 (SBCT) powders were prepared via solid-state reaction method. X-ray diffraction analysis reveals that the SBCN and SBCT powders have the single phase orthorhom-bic Aurivillius structure at room temperature. The contribution of Raman scattering and FTIR spectroscopy of these samples were relatively smooth and resemble each other. The calcined powders were uniaxially pressed and sintered at 1250?C for 8 h to obtaine dense ceramics. Dielectric constant, loss tangent and AC conductivity of the sintered Ce-doped SrBi2Nb2O9 and SrBi2Ta2O9 ceramics were measured by LCR meter. The Ce-doped SBN (SBCN) ceramics have a higher Curie temperature (TC) and dielectric constant at TC (380?C and ?? ~3510) compared to the Ce-doped SBT (SBCT) ceramics (330?C and ?? ~115) when measured at 100Hz. However, the Ce-doped SBT (SBCT) ceramics have lower conductivity and dielectric loss.

Preparation and electrical properties of (1−x)SrBi2Nb2O9−xBiFeO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics, (1−x)SrBi2Nb2O9−xBiFeO3 [(1−x)SBN−xBFO] (x=0.0, 0.03, 0.05, 0.07, 0.10) were prepared by a conventional solid-state reaction method. The crystal structure, microstructure and electrical properties were systematically investigated. All compositions formed layered perovskite structure without any detectable secondary phases. Plate-like morphology of the grains which is characteristic for layer-structure Aurivillius compounds was clearly observed. The excellent electrical properties (e.g., d33~19pC/N, 2Pr~18.8μC/cm2) and a high Curie temperature (e.g., Tc~449°C) were simultaneously obtained in the ceramics with x=0.05. Additionally, thermal annealing studies indicated that the BFO modified SBN ceramics system possessed stable piezoelectric properties, demonstrating that the modified SBN-based ceramics are the promising candidates for high-temperature applications.

Polarization fatigue in ferroelectric Pb(Zr0.52Ti0.48)O3-SrBi2Nb2O9 ceramics

Ferroelectric fatigue induced by cyclic electric loading of the (1-x)PZT-xSBN ceramics (0.1 ≤ x ≤ 0.3) have been investigated in comparison with pure PZT and SBN ceramics. The results showed that pure PZT ceramic possessed severe polarization fatigue after long bipolar switching pulses. This was mainly attributed to the appearance of microstructural damage at the near-electrode regions. Whereas, pure SBN ceramic exhibited no fatigue at least up to 1 × 106 switching cycles. The fatigue-free behavior of SBN ceramics was due primarily to weak domain wall pinning. PZT-SBN ceramics showed less polarization fatigue up to 1 × 106 switching cycles than pure PZT. This could be attributed to their low oxygen vacancy concentration. Therefore, this new ceramic PZT-SBN system seems to be an alternative material for replacing PZT in ferroelectric memory applications.

Microstructure and Dielectric Properties of (Ba, Ta) Co-Doped Sr<sub>2</sub>Nb<sub>2</sub>O<sub>7</sub> Ceramics

(Sr1-xBax) 2(Nb0.9Ta0.1) 2O7 (SBNT) ceramics were prepared by solid state reaction. The crystal structure of SBNT ceramics, surface morphology and dielectric properties were studied using XRD, SEM and LCR instrument analyzer, respectively. The results show that the grain size decreases with increasing Ba concentration, and all samples show single phase, no second phase can been observed. Addition of Ba ion can improve the dielectric properties of SBN ceramics. The dielectric constant increases first, then decreases; the maximum value (εr=97) can be obtained at x=0.1, the dielectric constant changes slightly with increasing wide frequency.

Influence of Sr/Ba ratio on the dielectric, ferroelectric and pyroelectric properties of strontium barium niobate ceramics

SrxBa1−xNb2O6 (with x=0.50, 0.45, 0.40 and 0.30) ceramics were synthesized by conventional solid-state method and sintered at 1350°C for 3h. The phase structure, microstructure, dielectric, ferroelectric and pyroelectric properties of obtained ceramics were systematically investigated. Pure tungsten bronze phase could be obtained in all ceramics. The dielectric characteristics showed that SBN ceramic was a relaxor with strong diffuse phase transition and weak frequency dispersion. As Sr molar fraction x increases from 0.30 to 0.50, the transition temperature TC decreased linearly while the diffusivity parameter γ declined from 1.88 to 1.68. The saturated polarization, remnant polarization and pyroelectric coefficient were also found to be enhanced in SBN ceramics with increasing Sr content. The pyroelectric coefficient of about 2×10−8C/cm2K can be obtained for polarized SBN50 ceramics at room temperature.

Structural, dielectric and ferroelectric properties of SBN ceramics synthesized by microwave reactive sintering technique

Strontium barium niobate (SrxBa1−xNb2O6 with x=0.53/SBN53) ceramics have been synthesized by microwave reactive sintering technique. Powders corresponding to SBN53 stoichiometric composition were calcined at 1200°C for 20, 30 and 45min; and the green pellets made of calcined powders were sintered at 1300°C for 20, 30 and 40min in a microwave furnace. Ceramics with tungsten bronze type crystal structure were obtained in relatively much less processing time as compared to conventional processing. The reaction between strontium niobate (SN) and barium niobate (BN) phases present in the calcined powders enhances the densification process of the ceramics during sintering. A relative density ∼98.3% was obtained in SBN53 ceramics sintered for 40min. Curie transition temperature (Tc) and dielectric constant (ɛr) were found to vary from 113 to 135°C and from 1350 to 2500, respectively, depending on the processing conditions.

Optical properties of rare-earth doped epitaxial Sr 0.5Ba 0.5Nb 2O 6 thin films grown by pulsed laser deposition

Optical quality rare-earth (RE) (Nd 3+, Eu 3+, Gd 3+ and Yb 3+) doped Sr 0.5Ba 0.5Nb 2O 6 (SBN) epitaxial films of ~ 170 nm thick have been successfully grown on MgO (100) single crystal substrates using pulsed laser deposition technique. Strong residual stress in these films has been revealed by Raman spectroscopic studies. Two kinds of in-plane orientations with respect to the MgO substrate co-exist. All the film samples show high transparency in the visible wavelength. Their band-gap energies appear to be independent of the types of dopant. Photoluminescence (PL) spectra of RE-doped SBN ceramics show a strong and broad emission band at around 600 nm (2.07 eV). The peak position of this emission band changes slightly with different RE-dopants. Thin film samples, however, yield a broad PL band at around 385 nm (3.22 eV). This UV emission shows no observable shift in the peak position for different dopants. Apart from these broad emission bands, conspicuous emission lines from Eu 3+ and Nd 3+ ions are also noted. The origins of these PL spectra are discussed.

Effect of vanadium doping on sintering and dielectric properties of strontium barium niobate ceramics

Strontium barium niobate, Sr0.5Ba0.5Nb2O6 (SBN50) ceramics doping up to 3 wt% V2O5 were fabricated by solid state reaction route, starting from raw materials (oxides and carbonates) of analytical grade. The phase composition, microstructure and dielectric properties were investigated by X-ray diffraction, scanning electric microscope and impedance analyzer. The results show that the addition of V2O5 improves sintering densification of SBN ceramic samples. The relative density of the samples firstly increases and then slightly decreases with increasing amounts of V2O5 and sintering temperature. With the help of the additive of 1 wt% V2O5, the relative density of the sample sintered at 1,280 °C for 3 h can reached 97.2%. Only single tetragonal tungsten bronze phase SBN exists in all the doped samples. With increase in V2O5 content, the dielectric constant of SBN ceramics at both room temperature and in the vicinity of the phase transition temperature increases significantly and the Curie temperatures (Tc) obviously shifts to low temperature as well as the dielectric loss remains below 0.06. The diffuseness in the phase transition is found to increase with increase in vanadium doping level. The addition of V2O5 results in an increased grain size associated with rod-like grain growth.

High-power piezoelectric characteristics of textured bismuth layer structured ferroelectric ceramics

Abstract-The high-power piezoelectric characteristics in h001i oriented ceramics of bismuth layer structured ferroelectrics (BLSF), SrBi(2)Nb(2)O(9) (SBN), (Bi,La)(4)Ti(3)O(12) (BLT), and CaBi(4)Ti(4)O(15) (CBT), were studied by a constant voltage driving method. These textured ceramics were fabricated by a templated grain growth (TGG) method, and their Lotgering factors were 95%, 97%, and 99%, respectively. The vibration velocities of the longitudinal mode (33-mode) increased proportionally to an applied electric field up to 2.5 m/s in these textured BLSF ceramics, although, the vibration velocity of the 33-mode was saturated at more than 1.0 m/s in the Pb(Mn,Nb)O(3)-PZT ceramics. The resonant frequencies were constant up to the vibration velocity of 2.5 m/s in the SBN and CBT textured ceramics; however, the resonant frequency decreased with increasing over the vibration velocity of 1.5 m/s in the BLT textured ceramics. The dissipation power density of the BLT was almost the same as that of the Pb(Mn,Nb)O(3)-PZT ceramics. However, the dissipation power densities of the SBN and CBT were lower than those of the BLT and Pb(Mn,Nb)O(3)-PZT ceramics. The textured SBN and CBT ceramics are good candidates for high-power piezoelectric applications.

Influence of substitution on dielectric and impedance spectroscopy of Sr 1 − xBi 2 + yNb 2O 9 ferroelectric ceramics synthesized by chemical route

Nanocrystalline powders of Sr 1 − x Bi 2 + y Nb 2O 9 (SBN, x = 0.0, 0.1, 0.2, 0.3, and 0.4; y = 0, 0.066, 0.133, 0.200, and 0.266) were prepared by aqueous solution method using water-soluble Sr–EDTA, Bi–EDTA and Nb–tartarate as the starting materials. XRD showed that the samples were free from fluorite or pyrochlore phase within heat-treatment temperature from 550 to 600 °C. Average crystallite size and particle diameter were observed to be between 10 and 25 nm, which were analyzed through XRD and TEM, respectively. Bi-substitution has substantially improved the sinterability of SBN and enabled to achieve high density (96%), which was otherwise difficult in the case of pure SBN. The dielectric properties of SBN ceramics were significantly enhanced by the partial replacement of Sr 2+ ions by the trivalent bismuth ions. The complex impedance diagrams of Bi-substituted SBN, x = 0.4 ceramics exhibited only one semicircle indicating a significant contribution from the grains. In contrast, the impedance plots for pure and other substituted SBN ceramics show an additional low-frequency semicircle, which was attributed to the blocker size effects. The dielectric behavior of pure and Bi-substituted SBN ceramics was rationalized using the impedance and modulus data.