Growth,microstructure, energy–storage and dielectric performances of chemical–solution NBT–based thin films: Effect of sodium nonstoichimometry

Na_0.5+δBi_0.5(Ti_0.96W_0.01Ni_0.03)O₃ thin films with various Na contents (abbreviated as Na_.5+δBTWN, δ?=?? 3.0, ??1.5, 0, 1.5%) were fabricated on ITO/glass substrates using a chemical–solution process. The effects of Na nonstoichiometry on the microstructure, insulating, ferroelectric and dielectric performances are investigated. The pure perovskite phase can be obtained in Na_0.5BTWN and Na_0.515BTWN, while for Na_0.470BTWN or Na_0.485BTWN, the main composition contains secondary phase of TiO₂. The grain size increases from 30?nm at δ?=?? 3.0% to 55?nm at δ?=?0%, then decreases to 52?nm with δ?=?1.5%. The leakage current of Na_0.485BTWN sample is reduced dramatically in comparison with Na_0.5+δBTWN (δ?=?? 3.0, 0, 1.5%). The big recoverable energy–storage density of 63.1?J/cm² and high energy–storage efficiency of 55.0% can be obtained for Na_0.485BTWN due to the improved electric break–down strength and large difference value between the remanent polarization and maximum polarization. Enhanced dielectricity is achieved in Na_0.485BTWN with a high tunability of 36.0% and a figure of merit of 4.0 at 450?kV/cm and 500?kHz. These results demonstrated that the crystallization, micrographs and energy storage and dielectric properties of Na_0.5Bi_0.5TiO₃ are highly sensitive to low levels of Na–site nonstoichiometry.     

Temperature-stable dielectric ceramics based on Na0.5Bi0.5TiO3

Multiple ion substitutions to Na_0.5Bi_0.5TiO₃ give rise to favourable dielectric properties over the technologically important temperature range ?55?°C to 300?°C. A relative permittivity, ε_r,?=?1300?±?15% was recorded, with low loss tangent, tanδ?≤?0.025, for temperatures from 310?°C to 0?°C, tanδ increasing to 0.05 at ?55?°C (1?kHz) in the targeted solid solution (1–x)[0.85Na_0.5Bi_0.5TiO₃–0.15Ba_0.8Ca_0.2Ti_1-yZr_yO₃]–xNaNbO₃: x?=?0.3, y?=?0.2. The ε_r-T plots for NaNbO₃ contents x?<?0.2 exhibited a frequency-dependent inflection below the temperature of a broad dielectric peak. Higher levels of niobate substitution resulted in a single peak with frequency dispersion, typical of a normal relaxor ferroelectric. Experimental trends in properties suggest that the dielectric inflection is the true relaxor dielectric peak and appears as an inflection due to overlap with an independent broad dielectric peak. Process-related cation and oxygen vacancies and their possible contributions to dielectric properties are discussed.     

Enhanced photodielectric effect in (0.88–x)Bi0.5Na0.5TiO3–0.12BaTiO3 –xBa(Ti0.5Ni0.5)O3–δ (BNBTNO) ceramics

In this work, solid solutions of (0.88–x)Bi_0.5Na_0.5TiO₃–0.12BaTiO₃– xBa(Ti_0.5Ni_0.5)O_3–δ were designed and prepared. These compositions exhibit ferroelectricity at room temperature, with the tetragonal symmetry. The c/a values are varied from ～1.0067 (x?=?0.1) to ～1.0208 (x?=?0.04). A transition from the high–temperature relaxor state to the low–temperature ferroelectric state is demonstrated by the temperature dependence of dielectric data and Raman spectrum. The direct bandgap decreases from 3.40?eV for x?=?0 to 3.16?eV for x?=?0.1. The Ba(Ti_0.5Ni_0.5)O_3–δ addition leads an additional optical absorption peak in the visible range. The obvious photodielectric effect was discovered. In particular, the relative permittivity of the x?=?0.1 composition rises from ～756 to ～807 under light illumination.     

Microstructure and electrical conductivity of A-site fully stoichiometric Na0.5+xBi0.5−xTiO3−δ with different Na/Bi ratios

The effect of nominal Na/Bi ratio on the microstructure and electrical conductivity of A-site fully stoichiometric sodium bismuth titanates, Na_0.5+xBi_0.5?xTiO_3?δ, was investigated in this study. Bulk samples with x?=?0, 0.01, 0.03, 0.05, 0.07, and 0.1 were prepared by conventional solid state reaction method. The as-calcined powders primarily exhibited the perovskite structure, which was identified by X-ray diffraction. Electron microscopic investigation of the sintered samples, however, revealed the presence of secondary phases, the amounts of which were found to increase with increasing Na/Bi ratio. Further elemental analysis by energy dispersive spectroscopy indicated that the secondary phases were mainly composed of sodium titanates with different Na/Ti ratios. The grain bulk and grain boundary conductivities of Na_0.5+xBi_0.5?xTiO_3?δ, measured by two-probe AC electrochemical impedance spectroscopy, significantly increased with increasing Na/Bi ratio when x?≤?0.03, but remained almost constant at higher x. The synergetic effect of oxygen vacancy creation, grain size reduction, and secondary phase formation on the variation in the conductivity upon increasing the nominal Na/Bi ratio in Na_0.5+xBi_0.5?xTiO_3?δ was discussed.     

Tailoring structural and electrical properties of A-site non-stoichiometric Na0.5Bi0.5TiO3 ceramic at different sintering temperature

Na/Bi stoichiometry plays crucial role in determining various properties of sodium bismuth titanate-based system. In this work, we have synthesised lead free (Na_0.5Bi_0.5)_1+x TiO₃ (x?=?0, 0.02 and 0.05) ceramics by sol-gel method and systematically presented structural, dielectric and ferroelectric properties at different sintering temperature. Single phase perovskite structure with rhombohedral symmetry (R3c) is obtained for all compositions from low (850°C) to maximum (1150°C) sintering temperature. The shifting of x-ray diffraction peaks and characteristic perovskite metal-oxide vibrational band (～627?cm^?1) in Fourier Transform Infra-red spectra suggests compression or expansion of crystal lattice with Na/Bi non-stoichiometry. Excess of Na/Bi comprises dense crystal growth as compared to pure Na_0.5Bi_0.5TiO₃ composition suggesting compensation of volatile elements loss during heat treatment whose impact has also been observed in dielectric as well as ferroelectric properties. It is observed that Na_0.51Bi_0.51TiO₃ sample with x?=?0.02 exhibits better structural, dielectric and ferroelectric properties in whole range of sintering temperature.     

Electrostatic energy storage performances of La(Ni2/3Ta1/3)O3-modified Na0.5Bi0.5TiO3 lead-free ceramics

Ceramic capacitors with high electrostatic energy storage performances have captured much research interest in latest years. Sodium bismuth titanate (Na_0.5Bi_0.5TiO₃)-based ferroelectric ceramics show great potential due to their environment-friendly composition, high polarization, and excellent relaxor properties. However, the nonergodic relaxor state of Na_0.5Bi_0.5TiO₃-based ceramics hampers the decrement of remanent polarization, leading to poor energy storage performance. Herein, the (1 − x)Na_0.5Bi_0.5TiO₃–xLa(Ni_2/3Ta_1/3)O₃ ceramics were designed to generate the transformation between nonergodic and ergodic relaxor state. As a result, the ceramics exhibit improved dielectric relaxation, slim polarization–electric field loops, and flattened current–electric field curves due to highly dynamic polar nanoregions. Particularly, the 0.85Na_0.5Bi_0.5TiO₃–0.15La(Ni_2/3Ta_1/3)O₃ ceramics show large breakdown electric field E_b (345 kV/cm), high recoverable energy density W_rec (3.6 J/cm³), and efficiency η (80.6%), revealing potential applications in electrostatic energy storage.     

Dielectric and optical properties of Ni doped Na0.5Bi0.5TiO3

Polycrystalline Ni doped Na_.5Bi_0.5TiO₃ samples (Na_0.5Bi_0.5)Ti_1-xNi_xO_3, (x?=?0.5, 0.10, 0.15) have been prepared by solid state reaction. The appearance of the additional peak in X-ray diffraction pattern indicates the ordering of Ti⁴⁺ and Ni²⁺ ions. Polygonal grains are converted into flakes with an increase of Ni concentration. Replacement of Ti⁴⁺ by Ni²⁺ strongly modifies the relative contribution of two peaks in the Raman bands within 200–400?cm^?1. Oxygen vacancy is observed in X-ray photoelectron spectrum to maintain charge neutrality due to aliovalent doping. Broad diffuse phase transition centered at the dielectric constant maximum indicates relaxor behaviour. Comparison between impedance and electric modulus spectrum suggests non-Debye relaxation. The ac conductivity follows the power law with the frequency exponent lies 0.52???0.72. The generation of holes by divalent Ni dopant at tetravalent Ti sites enhances optical band gap.     

Dielectric stability in the relaxor: Na0.5Bi0.5TiO3-Ba0.8Ca0.2TiO3-Bi(Mg0.5Ti0.5)O3- NaNbO3 ceramic system

Ceramics with temperature-stable dielectric characteristics have been developed in the system: 0.6[0.85Na_0.5Bi_0.5TiO₃-(0.15-x)Ba_0.8Ca_0.2TiO₃-xBi(Mg_0.5Ti_0.5)O₃]?0.4NaNbO₃, x ≤ 0.15. Dielectric measurements exhibited relaxor ferroelectric characteristics with temperature-stable relative permittivity from ε_r~1330 ± 15% in the temperature range from ?70?°C to 215?°C and tanδ ≤ 0.02 from ?20?°C to 380?°C for x = 0 compositions. For the Bi(Mg_0.5Ti_0.5)O₃ modified compositions the temperature range of stable relative permittivity extended from ?70?°C to 400?°C, with ε_r ~ 950 ± 15% and tanδ ≤ 0.02 from ?70?°C to 260?°C. Values of dc resistivity were ~ 10⁸ Ω?m at a temperature of 300?°C and the corresponding RC constant values were in the range from 0.40 ? 0.78?s at 300?°C. All ceramic samples exhibited a linear polarisation-electric field response at maximum applied electric field of 5?kV/cm (1?kHz).     

Low‐Temperature Dielectric Relaxations Associated with Mixed‐Valent Structure in Na0.5Bi0.5Cu3Ti4O12

We, herein, present comparative investigations on the Na_0.5Bi_0.5Cu₃Ti₄O₁₂ ceramic samples with and without 10 mol% excess of Na/Bi. The samples were prepared by the standard solid‐state reaction technique. The dielectric properties of the sample were investigated in the temperature (93–320 K) and frequency (20 Hz–10 MHz) windows. Three thermally activated dielectric relaxations observed in Na_0.5Bi_0.5Cu₃Ti₄O₁₂ with the activation energies of 0.104, 0.267, and 0.365 eV for the low‐, middle‐, and high‐temperature dielectric relaxations, respectively. Only the low‐temperature relaxation was observed in both Na and Bi excessive samples. X‐ray photoemission spectroscopy results revealed the mixed‐valent structures of Cu⁺/Cu²⁺ and Ti³⁺/Ti⁴⁺ in Na_0.5Bi_0.5Cu₃Ti₄O₁₂ sample, but only Ti³⁺/Ti⁴⁺ in Na and Bi excessive samples. Our results showed that the dielectric properties of the investigated samples are strongly linked with these mixed‐valent structures. The high‐ and low‐temperature relaxations were attributed to be a polaron‐type relaxation due to localized carriers hopping between Cu⁺/Cu²⁺ and Ti³⁺/Ti⁴⁺, respectively. The middle‐temperature relaxation is suggested to be a dipole‐type relaxation caused by the defect complex of bismuth and oxygen vacancies.     

Polarization behavior of` lead-free 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 thin films with enhanced ferroelectric properties

(Bi_0.5Na_0.5)TiO₃ based ferroelectric lead-free thin films have great potential for modern micro-devices. However, the multicomponent feature and volatile nature of Bi/Na makes the achievement of high quality films challenging. In this work, the morphotropic phase boundary composition, 0.94(Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃ thin films were successfully prepared by CSD method. Dense films with low dielectric loss and low leakage current density were obtained. A well-defined polarization hysteresis loop with a high remnant polarization was observed in the thin films. Moreover, the polarization behavior of the film at original state, under electric field and upon heating was investigated by PFM. A self-polarization and asymmetric domain switching behavior were observed. High temperature induced depolarization and the self-polarization recovered upon cooling. The thin films with good quality show a promising potential for the application in electrical devices, and the in-depth investigation of the polarization behavior improves the understanding of ferroelectric and piezoelectric properties of thin films.     

Realizing excellent energy storage properties in Na0.5Bi0.5TiO3-based lead-free relaxor ferroelectrics

Development of lead-free dielectric capacitors with high recoverable energy storage density (W_rec), large energy storage efficiency (η), and wide usage temperature range are in high demanded for pulse power systems. Herein, we realized the enhancement of energy storage properties [high W_rec = 3.76 J/cm³, large η = 78.80 %, and broad operating temperature range (20?180 °C)] in lead-free Na_0.5Bi_0.5TiO₃ (BNT)-based relaxor ferroelectrics via component regulation. Excellent energy storage properties mainly originate from suppressing early polarization saturation and improving dielectric breakdown strength (E_b). Domain evolution on the nanoscale offers robust support to suppression of early polarization saturation. The enhancement of E_b can be derived from the contribution of the Mg-rich phase, which is also corroborative via first-principles calculation on basis of density functional theory (DFT). We believe that these findings in this work may provide a practicable guideline to build new lead-free ceramics for electrical energy storage applications.     

Molten salt synthesis and characterization of lead-free (1-x)Na0.5Bi0.5TiO3-xSrTiO3 (x = 0, 0.10, 0.26) whiskers

In this study, Na_0.5Bi_0.5TiO₃-xSrTiO₃ (NBT-xST, x?=?0, 0.10, 0.26) whiskers were synthesized by a two step molten salt method using Na₂Ti₆O₁₃ whiskers as templates. The crystalline phase, morphology, microstructure, composition and ferroelectric characteristic of the whiskers were investigated in details. The topochemical transformation from Na₂Ti₆O₁₃ structure to NBT-xST perovskite structure was found to occur by structural rearrangement of the edge sharing octahedra into vertex sharing octahedra. The prepared polycrystalline NBT-xST whiskers possessed high aspect ratio with diameter of 500–800?nm and length of 5–10?µm. The PFM investigations confirmed the favorable piezoelectricity of NBT whiskers while the NBT-0.26ST whiskers displayed relaxor-ferroelectric characteristics at room temperature, exhibiting the potential of NBT-xST whiskers for fabricating high performance micro/nano-devices.     

Tailoring structural and electrical properties of A-site nonstoichiometric Na0.5Bi0.5(Ti0.97Ni0.03)O3 ferroelectric films deposited on LaNiO3(100)/Si substrate

Highly (l00)-oriented Ni-doped Na_0.5Bi_0.5TiO₃ (NBTNi) thin films with different A-site cation nonstoichiometry were deposited on the LaNiO₃ (100)/Si substrates. We find that low levels of Na/Bi nonstoichiometry in the original composition of NBTNi films have obvious influence on the crystal structure and ferro-/dielectric properties. Na deficiency or Bi excess can lower the leakage current compared to the stoichiometric sample due to the decreased oxide-site vacancies. However, the mechanisms for the two types of films are different. That is, the mobile oxygen vacancies are tied by the Na vacancies in Na deficiency film whereas the formation of oxygen vacancies is suppressed for Bi-rich film. A good combination of ferroelectric property (P_r = 22.7?μC/cm²) and dielectric property (ε_r = 360 and tan?δ?=?0.11) can be achieved in Bi-rich NBTNi (Na_0.5Bi_0.54TNi) film. Besides, the effect of voltage and frequency on the capacitance and dielectric tunability for the Na_0.5Bi_0.54TNi film is investigated solely. These results show that NBT-based thin film is quite flexible in A-site nonstoichiometry, which provides a broad space for performance improvement.     

Piezoelectric enhancement and vacancy defect reduction of lead-free Bi0.5Na0.5TiO3-based thin films

To explore new lead-free piezoelectric materials that is both environmentally friendly and healthy to provide the possibility for material selection for microelectromechanical systems. Lead-free piezoelectric (1-x)(0.8Bi_0.5Na_0.5TiO₃-0.2Bi_0.5K_0.5TiO₃)-xBi(Ni_0.5Zr_0.5)O₃ thin films (abbreviated as BNT-BKT-xBNZ) (x=0.00, 0.01, 0.02, 0.03, 0.04) were prepared on Pt(111)/Ti/SiO₂/Si substrates by a sol-gel method. Impacts of Bi(Ni_0.5Zr_0.5)O₃ content on the microstructure, dielectric, ferroelectric, and piezoelectric properties were also investigated detailedly. It found that the Bi(Ni_0.5Zr_0.5)O₃ composition had a great influence on the increase of relaxor and the decrease of the oxygen vacancies, which is influential to the promotion of thin-film properties. Thin-film of BNT-BKT-0.02BNZ showed the optimum electrical properties with the polarization of 40.27 μC/cm², dielectric constants of 477 and effective inverse piezoelectric coefficient reach up to 125.9 p.m./V. Results revealed that the BNT-BKT thin films with 0.02 mol% Bi(Ni_0.5Zr_0.5)O₃-doped are a kind of lead-free piezoelectric materials with superior manifestations with a great development prospect for applications.     

Enhanced energy storage density and discharge efficiency in potassium sodium niobite-based ceramics prepared using a new scheme

The development of lead-free ceramics with high recoverable energy density (W_rec) and high energy storage efficiency (η) is of great significance to the current energy situation. In this work, a new scheme was proposed to improve the W_rec and η of potassium sodium niobate ((K, Na)NbO₃, abbreviated as KNN) lead-free ceramics. Doping Bi elements in KNN ceramics to form a second phase (K₂BiNb₅O₁₅) can reduce the grain size and form Schottky-like contact. Meanwhile, the hybridization between the Bi 6p and O 2p orbitals can enhance the maximum polarization (P_max). So the K_1-3xBi_xNa_0.5NbO₃-1 mol%CuO ceramics was proposed to improve the W_rec of lead-free ceramics. A large W_rec (2.89 J/cm³) and dielectric breakdown strength (DBS) (300 kV/cm with a thickness of 0.2 mm) were achieved for K_0.14Bi_0.12Na_0.5NbO₃-1 mol%CuO ceramics. The high W_rec was supposed to benefit from low remnant polarization (P_r), high Ps and DBS of ceramics. In addition, a large η (80%) was simultaneously achieved for K_1-3xBi_xNa_0.5NbO₃-1 mol%CuO ceramics, which is superior to mostly reported lead-free bulk ceramics. The results show that K_1-3xBi_xNa_0.5NbO₃-1 mol%CuO ceramics have a good application prospect in the field of energy storage, and provide a new scheme for the preparation of lead-free ceramics with high energy storage density and high conversion efficiency.     

High energy storage density and efficiency in (Bi0.5Na0.5)0.94Ba0.06TiO3-based ceramics with broadened and flattened dielectric peaks

Currently, Bi_0.5Na_0.5TiO₃-based lead-free ferroelectrics have attracted considerable attention as one of the promising candidates for dielectric materials due to their large spontaneous polarization, environmental friendliness and low cost. However, their poor energy density hinder the practical application of the materials. Herein, a novel ceramic of (1-x) (0.94Bi_0.5Na_0.5TiO₃-0.06BaTiO₃)-x(0.96NaNbO₃-0.04CaSnO₃) (BNBT-xNNCS) has been developed by the solid solution of antiferroelectric NaNbO₃–CaSnO₃ into ferroelectric Bi_0.5Na_0.5TiO₃–BaTiO₃ and the microstructure and electrical properties of the material have been systematically investigated. All the ceramics are lied within the coexistence zone of tetragonal (T) and rhombohedral (R) phases, ensuring to the large polarizations of the materials. Importantly, the introduction of NaNbO₃–CaSnO₃ shifts dielectric peaks at T_s towards room temperature and simultaneously broadens and flattens the dielectric peaks, destroying the ferroelectric long-range order of ferroelectric domains and inducing the generation of polar nanoregions (PNRs) to reduce the remanent polarization. As a result, the prominent energy storage properties with the charge energy storage density (W_tot) of 1.86 J/cm³, recoverable energy density (W_rec) of 1.64 J/cm³ and energy storage efficiency (η) of 88.23% are obtained in the BNBT-xNNCS ceramics with x = 0.20 (BNBT-20NNCS) under a comparatively low electric field strength of 149 kV/cm, accompanying with superior frequency (ΔW_rec ≤ 3%, Δη ≤ 3%, 30–90 Hz) and thermal stability (ΔW_rec ≤ 10%, Δη ≤ 10%, 25–175 °C).     

Enhanced energy storage in temperature stable Bi0.5Na0.5TiO3-modified BaTiO3-Bi(Zn2/3Nb1/3)O3 ceramics

Recently, BaTiO₃-BiMeO₃ ceramics have garnered focused research attention due to their outstanding performance, such as thermal stability, energy efficiency and rapid charge-discharge behavior, however, a lower recoverable energy storage density (W_rec) caused by a relatively low P_max (<30 μC/cm²) mainly hinders practical applications. Herein, the energy density and thermal stability are improved by adding a tertiary component, i.e., Bi_0.5Na_0.5TiO₃, into BaTiO₃-BiMeO₃, resulting in xBi_0.5Na_0.5TiO₃-modified 0.88BaTiO₃-0.12Bi(Zn_2/3Nb_1/3)O₃ ceramics, with x = 0, 0.1, 0.2, 0.3 and 0.4, with superior dielectric properties and eco-friendly impact. Incorporating Bi_0.5Na_0.5TiO₃ with a high saturation polarization and Curie temperature not only significantly enhances P_max of BaTiO₃-Bi(Zn_2/3Nb_1/3)O₃ but also improves Curie temperature of (1-x)[0.88BaTiO₃-0.12Bi(Zn_2/3Nb_1/3)O₃]-xBi_0.5Na_0.5TiO₃ system. Combined with complementary advantages, modified ceramics render a superior energy storage performance (ESP) with a high W_rec of 3.82 J/cm³, efficiency η of 94.4% and prominent temperature tolerance of 25–200 °C at x = 0.3. Moreover, this ceramic exhibit excellent pulse performance, realizing discharge energy storage density W_dis of 2.31 J/cm³ and t_0.9 of 244 ns. Overall, the proposed strategy effectively improved comprehensive properties of BaTiO₃-based ceramics, showing promise in next-generation pulse applications.     

Bi(Mg0.5Ti0.5)O3 addition induced high recoverable energy-storage density and excellent electrical properties in lead-free Na0.5Bi0.5TiO3-based thick films

(1-x)Na_0.5Bi_0.5TiO₃-xBi(Mg_0.5Ti_0.5)O₃ (NBT-BMT) thick films were designed for achieving large recoverable energy-storage density (W_rec). A large W_rec of 40.4 J/cm³ was detected in the thick film for x = 0.4, which was more than 4 times larger than that of the pure NBT film. The addition of BMT induced slim polarization hysteresis (P-E) loops at room temperature. The slim P-E loops improved the difference between the maximum polarization (P_max) and the remnant polarization (P_r). Besides, a breakdown strength field (BDS) of 2440 kV/cm was also detected in the thick film for x = 0.4. The high BDS was caused by the reduced leakage current density. Furthermore, the thick film for x = 0.4 possessed superior energy-storage stability under different temperature, frequency and electric-field cycling. In addition, 90% of the pulsed discharge energy density could be released in less than 1100 ns by using a pulsed discharge measurement.     

Enhanced ferroelectric properties and thermal stability of Mn‐doped 0.96(Bi0.5 Na0.5)TiO3‐0.04BiAlO3 ceramics

(Bi_0.5Na_0.5)TiO₃–BiAlO₃ lead‐free materials exhibit excellent ferroelectric properties, but its depolarization temperature is relatively low which is the major obstacle limiting the material's practical application. In this study, the effects of Manganese (Mn) modification on the microstructure, ferroelectric properties and depolarization behavior of 0.96(Bi_0.5Na_0.5)(Ti_1?xMn_x)O₃–0.04BiAlO₃ ceramics were investigated. It was found that the average grain size was enlarged and ferroelectric properties were enhanced with small Mn addition, meanwhile the tangent loss decreased. The remnant polarization (P_r) of the samples reached an optimal value (~41 μC/cm²) as Mn content increased up to 0.7 mol%, whereas further addition resulted in the decrease in P_r. Moreover, appropriate Mn addition (x=0.7%) can improve the depolarization temperature from 140°C to 161°C determined from thermally stimulated depolarization currents measurement.     

High energy storage performance of [(Bi0.5Na0.5)0.94Ba0.06]0.97La0.03Ti1-x(Al0.5Nb0.5)xO3 ceramics with enhanced dielectric breakdown strength

Novel lead-free [(Bi_0.5Na_0.5)_0.94Ba_0.06]_0.97La_0.03Ti_1-x(Al_0.5Nb_0.5)_xO₃ ceramics (BNBLT-xAN) were prepared by the conventional solid state sintering method. The dielectric, ferroelectric, ac impedance and energy-storage performance were systematically investigated. Temperature dependent permittivity curves showed that relaxation properties of sintered ceramics gradually diminished with the increase of AN. The introduction of AN gave rise to a slimmer polarization hysteresis loop (P-E) and an enhanced dielectric breakdown strength (DBS). Therefore, the optimum energy-storage performance were realized at x?=?0.05 with the energy-storage density (W_rec) of 1.72?J/cm³ and energy-storage efficiency (η) of 85.6% at 105?kV/cm, accompanied with the excellent temperature stability and fatigue performance. The results demonstrated that BNBLT-xAN system was a promising lead-free candidate for energy-storage applications.