Lead-free Ceramics Research Articles

Enhancement of Energy-Storage Properties and Temperature Stability in Complex Perovskite (1−x)NaNbO3−xBi(Li1/3Sn2/3)O3 Lead-Free Ceramics

In general, NaNbO3 (NN) ceramics are considered to be one of the most promising lead-free perovskites (AFE) materials with low cost, low density, and nontoxic advantages. However, the energy storage capability of this material is often greatly hindered by the hysteresis exhibited during the transition from the antiferroelectric to the ferroelectric phase. In this study, lead-free dielectric (1−x)NaNbO3−xBi(Li1/3Sn2/3)O3, x = 0.0 − 0.08, ceramics were synthesized by solid-state reaction method. The XRD data show a structural change from orthorhombic to pseudo-cubic at x = 0.06 composition. With increasing Bi(Li1/3Sn2/3)O3 content, changes in dielectric properties demonstrated that the AFE P phase was successively replaced by the relaxor AFE R phase, resulting in a thin P–E loop characteristic which leads to the improvement of the energy storage density and efficiency of the ceramic capacitors. The optimum recoverable energy storage density (W rec = 0.56 J/cm3) and efficiency (η = 74%) were obtained at x = 0.06 under an electric field of 120 kV/cm. The optimum composition also exhibited temperature stability in the range of 25 °C–100 °C. In addition, an increase in Bi(Li1/3Sn2/3)O3 content can lead to a decrease in leakage current density. This research shows that BLS modified NN ceramics are promising dielectric material candidates for energy storage applications.

Enhanced electrocaloric effect in KNN-based ceramic via polymorphic phase transition

A large adiabatic temperature change (ΔT) in lead-free ceramics is highly desired to develop eco-friendly and high efficiency solid-state refrigeration device based on electrocaloric effect (ECE). However, a large ΔT is often obtained near high Curie temperature (Tc > 100 °C), which impedes the practical applications for electrocaloric refrigeration technology. Herein, the lead-free (1-x)(K0.48Na0.535)0.03Li0.07(Nb0.99Sb0.01)O3-xBaZrO3 (x = 0, 0.02, 0.04 and 0.06) ceramics were synthesized through a conventional solid-state sintering method. A polymorphic phase transition (PPT) region is constructed by composition engineering to achieve large ECE near the ambient temperature. A ΔT of 0.48 K under 50 kV/cm is obtained at 60 °C by using the direct measurement in KNLNS-0.02BZ ceramic with coexistence of R-O-T phase. This work suggests that building multi-phase coexistence is a feasible design scheme in order to achieve ECE near the room temperature.

Ultrahigh Electrostrictive Effect in Lead-Free Ferroelectric Ceramics Via Texture Engineering.

The electrostrictive effect, which induces strain in ferroelectric ceramics, offers distinct advantages over its piezoelectric counterpart for high-precision actuator applications, including anhysteretic behavior even at high frequencies, rapid reaction times, and no requirement for poling. Historically, commercially available electrostrictive materials have been lead oxide-based. However, global restrictions on the use of lead in electronic components necessitate the exploration of lead-free electrostrictive ceramics with a high strain performance. Although various engineering strategies for producing materials with high strain have been proposed, they typically come at the expense of increased strain hysteresis. Here, we describe the extraordinary electrostrictive response of (Ba0.95Ca0.05)(Ti0.88Sn0.12)O3 (BCTS) ceramics with ultrahigh electrostrictive strain and negligible hysteresis achieved through texture engineering leveraging the anisotropic intrinsic lattice contribution. The BCTS ceramics exhibit a high unipolar strain of 0.175%, a substantial electrostrictive coefficient Q33 of 0.0715 m4 C-2, and an ultralow hysteresis of less than 0.8%. Notably, the Q33 value is three times greater than that of high-performance lead-based Pb(Mg1/3Nb2/3)O3 electrostrictive ceramics. Multiscale structural analyses demonstrate that the electrostrictive effect dominates the BCTS strain response. This research introduces a novel approach to texture engineering to enhance the electrostrictive effect, offering a promising paradigm for future advancements in this field.

Improved dielectric and piezoelectric thermal stability by chemical homogenization in CuO-modified 0.75BiFeO3-0.25BaTiO3 piezoceramics

0.75BiFeO3-0.25BaTiO3 lead-free ceramics have been considered promising candidates for high-temperature piezoelectric applications. However, their dielectric and piezoelectric properties severely degrade with increasing temperature. In this work, improved dielectric and piezoelectric thermal stability was obtained in CuO-modified 0.75BiFeO3-0.25BaTiO3 ceramics. CuO addition increases the volume fraction of the rhombohedral phase in the 0.75BiFeO3- 0.25BaTiO3 ceramics and makes the chemical heterogeneity disappear. The dielectric and piezoelectric anomalies are eliminated near 300 °C and return with CuO additions, and the temperature degradations of the dielectric constant and piezoelectric coefficient of 0.75BiFeO3-0.25BaTiO3 ceramics with 0.008 mol CuO in the range from 25 to 400 °C decrease by 85% and 60%, respectively. Furthermore, the depoling temperature and piezoelectric coefficient of 0.75BiFeO3-0.25BaTiO3 ceramics with 0.008 mol CuO are 570 °C and 131 pC/N, respectively. These results indicate that CuO addition is an effective approach to improve both the dielectric and piezoelectric thermal stability of 0.75BiFeO3-0.25BaTiO3 ceramics.

Ultrahigh Energy Storage Density and Efficiency of Lead-Free Dielectrics with Sandwich Structure.

Lead-free dielectric capacitors have attracted significant research interest for high-power applications due to their environmental benefits and ability to meet the demanding performance requirements of electronic devices. However, the development of lead-free ceramic dielectrics with outstanding energy storage performance remains a challenge. In this study, environmentally friendly ceramic dielectrics with sandwich structures are designed and fabricated to improve energy storage performance via the synergistic effect of different dielectrics. The chemical compositions of the outer and middle layers of the sandwich structure are 0.35BiFeO3 -0.65SrTiO3 and Bi0.39 Na0.36 Sr0.25 TiO3 , respectively. The experimental and theoretical simulation results demonstrate that the breakdown strength is over 700kVcm-1 for prepare sandwich structure ceramics. As a result, an ultrahigh recoverable energy storage density of 9.05Jcm-3 and a near-ideal energy storage efficiency of 97% are simultaneously achieved under 710kVcm-1 . Furthermore, the energy storage efficiency maintains high values (≥ 96%) within 1-100Hz and the power density as high as 188MWcm-3 under 400kVcm-1 . These results indicate that the designed lead-free ceramics with a sandwich structure possess superior comprehensive energy storage performance, making them promising lead-free candidates in the energy storage field.

A novel low-loss and high-stability (1-x)Na0.98NbO3–xBi(Al0.5Y0.5)O3 lead-free composite ceramics for dielectric energy storage capacitors

Environmentally friendly, high-performance, lead-free dielectric ceramic capacitors are urgently required for efficient and clean energy storage devices. However, most ferroelectric capacitors require excessively high electric fields to achieve large energy storage densities. In this study, we designed and fabricated a (1-x)Na0.98NbO3–xBi(Al0.5Y0.5)O3 (abbreviated as (1-x)NN-xBAY) composite system with different BAY doping levels using a traditional solid-state reaction method. By introducing 12 mol% BAY into nonstoichiometric NN, the polarization–electric field loop of the 0.88NN–0.12BAY ceramic became significantly slender and showed a superior relaxor behavior. Consequently, a remarkably low dielectric loss of tanδ < 0.005, high energy storage density of ∼ 4.64 J/cm3, and high efficiency of ∼ 85.98 % were simultaneously obtained in the 0.88NN–0.12BAY ceramic under a moderate electric field of 223.47 kV/cm. Furthermore, it exhibited ultrahigh stability in the temperature range of 25–200 °C and wide frequency range of 1–200 Hz, even after 108 electrical cycles. This study demonstrated a promising candidate material for energy storage devices operating under low or medium electric fields.

Achieving Ultrahigh Energy Storage Performance for NaNbO3-Based Lead-Free Antiferroelectric Ceramics via the Coupling of the Stable Antiferroelectric R Phase and Nanodomain Engineering.

NaNbO3(NN)-based lead-free eco-friendly antiferroelectric (AFE) ceramics with an extremely high maximum polarization (Pm) are believed to be a promising alternative to traditional lead-based ceramics. Nevertheless, the high energy dissipation resulting from the large polarization hysteresis, which arises from the AFE-ferroelectric (FE) phase transition, poses a great challenge to the application of this promising ceramic. Herein, an excellent recoverable energy storage density (Wrec) was attained by intentionally designing a (0.86 - x) NaNbO3-0.14CaTiO3-xBiMg2/3Nb1/3O3 (NN-CT-xBMN) relaxor antiferroelectric ceramic, attributed to the synergistic effect of the stable AFE R phase and nanodomain engineering to overcome the bottleneck. The obtained results illustrate that the inclusion of BMN causes the transition from AFE microdomains to nanodomains and stabilizes the relaxor AFE orthorhombic R phase, which generates a highly stable polarization field response with low hysteresis and delays the AFE-FE phase transition, thus improving energy storage density. As a consequence, a high Wrec of 5.41 J cm-3 with an excellent conversion efficiency η of 86.7% was obtained in the NN-CT-0.08BMN ceramic. Moreover, the NN-CT-0.08BMN ceramic exhibits superior stability in temperature (25-150 °C), frequency (1-600 Hz), and fatigue behavior (10°-104 cycles) together with a large current density (CD = 810 A cm-2), ultrahigh power density (PD = 118 MW cm-3), and ultrafast discharge rate (t0.9 < 0.7 μs). This superior energy storage density, coupled with outstanding stability, suggests that the NN-CT-0.08BMN ceramic has the potential to be a promising candidate for pulsed power applications and power electronics.

Exploration of the Structural, Dielectric, Ferroelectric, and Piezoelectric Properties in Non-stoichiometric Sr1−XBi2+2X/3Nb2O9 Ceramics

In this study, the authors focused on the preparation and characterization of Lead-free ferroelectric ceramics known as Sr1−XBi2+2X/3Nb2O9: SBBNX, where 0.0≤ × ≤0.4. The ceramics were synthesized using a conventional solid-state reaction route. The researchers performed X-ray diffraction (XRD) analysis to confirm the phase formation and employed the Rietveld refinement technique. The results indicated that the prepared SBBNX ceramics exhibited a single phase with an orthorhombic structure, specifically belonging to the A21am space group. All samples were subjected to analysis using field emission scanning electron microscopy (FESEM) to investigate their surface morphology. The micrographs revealed a uniform distribution of grains (of size 2–4 μm ) on the surface, with distinct grain boundaries. An increasing trend in both the dielectric constant (from 99 to 220 at room temperature) and transition temperature (from 396 °C to 490 °C) was noted with an increase of Bi content in SBN. The researchers estimated the activation energies by analyzing the Arrhenius plots of the ac conductivity. The obtained values ranged from 0.62 to 1.25 eV, indicating the presence of motion of oxygen vacancies in the SBBNX ceramics. The primary objective of this study was to optimize the Sr/Bi ratio in SBBNX ceramics to enhance their potential use in non-volatile random access memory (NVRAM) applications and high-temperature piezoelectric devices.

Multi-scale domain and microstructure engineering for the high-energy-storage BCZT based lead-free relaxor ferroelectric ceramics

Multi-scale domain and microstructure engineering for the high-energy-storage BCZT based lead-free relaxor ferroelectric ceramics

Tuning of defect structure and electrical properties for potassium sodium niobate lead-free ceramics with oxides

Tuning of defect structure and electrical properties for potassium sodium niobate lead-free ceramics with oxides

Enhancement of the Dielectric and Energy Storage Properties of Lead-Free BNSLT Ceramics by Zr4+ Substitution into B-Sites

(Bi0.38Na0.30Sr0.28)0.98La0.02Ti1-xZrxO3 (abbreviated as BNSLT1-xZrx, with x = 0 − 0.05) lead free ceramics were fabricated using the solid-state combustion method. The phase structure, microstructure and electrical properties of the ceramics were investigated. The coexistence of the rhombohedral (R) and tetragonal (T) phases was found in all samples. Rietveld refinement confirmed that as x increased from 0 to 0.05, the rhombohedral phase increased from 41 to 60%. A nearly equal R:T phase ratio of 49:51 was obtained for x = 0.01. All ceramics displayed polygonal grain shapes with anisotropic grain growth. The average grain size of the ceramics was in the range of 0.46–0.79 µm. The optimal Zr4+ content resulted in increased grain growth and reduced pores, leading to improved electrical properties. The highest density (5.52 g/cm3), maximum dielectric constant (ε m =2156), maximum polarization (Pmax=15.36 µC/cm2) and high energy storage properties (Wtotal=0.49 J/cm3, Wrec=0.45 J/cm3, Wloss=0.05 J/cm3 and η = 90.54% at 60 kV/cm) were obtained from x = 0.01 caused by a morphotropic phase boundary (MPB) and good morphology.

Phase Formation, Morphology and Electrical Properties of Lead-Free BNBLT-xBSN Ceramics Synthesized via the Solid-State Combustion Technique

Lead-free 1-x(Bi0.47Na0.47Ba0.06)0.95La0.05TiO3-xBa(Sn0.70Nb0.24)O3 (BNBLT-xBSN) ceramics with x = 0, 0.01, 0.02, 0.03 and 0.04 mol.% were synthesized by the solid-state combustion technique with a calcination temperature of 750 °C for 2 h and a sintering temperature of 1150 °C for 2 h. The effect of BSN substitution on the phase formation, microstructure, dielectric, ferroelectric and energy storage properties of the BNBLT ceramics was investigated. With the substitution of BSN, the coexisting rhombohedral (R) and tetragonal (T) phases transformed into coexisting R and cubic (C) phase, verified by Rietveld refinement. The C phase increased with increased BSN content. The average grain size decreased from 1.14 to 0.89 µm when x increased to 0.03 and then increased to 0.96 µm. The measured density and maximum dielectric constant (ε m) tended to increase from 5.44 to 5.87 g/cm3 and 1800 to 1942 when x increased to 0.03, then decreased to 5.25 g/cm3 and 1501, respectively. The remanent polarization (P r) and coercive field (E c) decreased when x increased to 0.03. The 0.97BNBLT-0.03BSN ceramic exhibited the lowest energy loss density (W loss ∼ 0.10 J/cm3) and the highest energy-storage efficiency (η ∼ 77.3%) measured under an electric field of 70 kV/cm.

Fabrication of 0.7BaTiO3-0.3Ni0.7Zn0.3Fe2O4 Multiferroic Composite Ceramics Prepared by the Solid-State Combustion Technique

Lead-free multiferroic composite ceramics of 0.7BaTiO3-0.3Ni0.7Zn0.3Fe2O4 (BT-NZF) were prepared by the solid-state combustion technique. The BT and NZF powders were calcined in the range of 1100 to 1200 °C for 4 h and 900 to 1100 °C for 2 h, respectively. Afterward, BT-NZF composite ceramics were sintered between 1100 and 1250 °C for 4 h. The effect of the firing temperature on the phase formation, microstructure, electrical, and magnetic properties of BT-NZF composite ceramics was investigated. X-ray diffraction of BT and NFZ powders showed the highest purity phase were prepared the calcination temperatures of 1100 and 1050 °C, respectively. The BT-NZF composite ceramics exhibited coexisting tetragonal perovskite and cubic spinel phases. The maximum density of 5.85 g/cm3 was obtained when sintering the composite ceramics at 1125 °C. The dielectric constant at room temperature increased with increased sintering temperature. The hysteresis loops showed leakage current in all samples. Ferromagnetic properties showed the highest Ms ∼ 24.56 emu/g measured under a magnetic field of 10,000 Oe from the sample sintered at 1150 °C.

Influence of Nb5+ Substitution on the Phase Formation, Microstructure and Electrical Properties of SBNLT Ceramics Synthesized via the Solid-State Combustion Technique

In this study, the phase formation, microstructure, and electrical properties of Sr0.3(Bi0.70Na0.67Li0.03)0.5(Ti1-xNbx)O3: SBNLT-Nbx lead-free ceramics synthesized via the solid state combustion technique were examined. SBNLT-Nbx ceramics with various Nb content of x = 0, 0.01, 0.03, and 0.05 were calcined at 750 °C and sintered at 1175 °C for 2 h, respectively. The SBNLT-Nbx calcined powders showed a perovskite structure and a secondary NbO2 phase was observed with Nb5+ content of 0.03 and 0.05 mol%. All SBNLT-Nbx ceramics exhibited a pure perovskite phase with coexisting rhombohedral and tetragonal phases. The grain size was in the range of 1.17-1.34 µm. The ε max and tan δ max tended to decrease with increased x content. The best ferroelectric and energy storage properties (P max = 27.45 µC/cm2, P r = 1.92 µC/cm2 and W total = 0.958 J/cm3, W rec = 0.739 J/cm3, W loss = 0.219 J/cm3, η = 77.1%), measured under an electric field of 70 kV/cm, were observed at x = 0.01.

Enhanced Electromechanical Performance in Lead-free (Na,K)NbO3-Based Piezoceramics via the Synergistic Design of Texture Engineering and Sm-Modification.

Next-generation electromechanical conversion devices have a significant demand for high-performance lead-free piezoelectric materials to meet environmentally friendly requirements. However, the low electromechanical properties of lead-free piezoceramics limit their application in high-end transducer applications. In this work, a 0.96K0.48Na0.52Nb0.96Sb0.04O3-0.04(Bi0.5-xSmx)Na0.5ZrO3 (abbreviated as T-NKN-xSm) ceramic was designed through phase regulation and texture engineering, which is expected to solve this difficulty. Through our research, we successfully demonstrated the enhanced electromechanical performance of lead-free textured ceramics with a highly oriented [001]c orientation. Notably, the T-NKN-xSm textured ceramics doped with 0.05 mol % Sm exhibited the optimal electromechanical performance: piezoelectric coefficient d33 ≈ 710 pC N-1, longitudinal electromechanical coupling k33 ≈ 0.88, planar electromechanical coupling kp ≈ 0.80, and Curie temperature Tc ≈ 244 °C. Finally, we conducted a detailed investigation into the phase and domain structures of the T-NKN-Sm ceramics, providing valuable insights for achieving high electromechanical properties in NKN-based ceramics. This research serves as a crucial reference for the development of advanced electromechanical devices by facilitating the utilization of lead-free piezoelectric materials with superior performance and environmental benefits.

Large electric field-induced strain and excellent photoluminescence properties of Pr-modified 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 lead-free ferroelectric ceramics

The 0.94Bi0.5-xPrxNa0.5TiO3-0.06BaTiO3 (BNT-6BT-xPr) lead-free ceramics with doping content of x = 0, 0.01, 0.025, 0.04, 0.05, 0.075, and 0.1 were synthesized by the conventional solid-state reaction method. After doping with the Pr element, a composition-induced phase transition took place, which from the rhombohedral perovskite (R3c) and tetragonal perovskite (P4bm) phases coexisting into the pseudo-cubic phase. At the same time, the introduction of the Pr element had a beneficial effect on grain growth, and the average size of the crystal particle increased from 299 to 742 nm. The Curie temperature Tm showed no obvious change with the increasing Pr content, but the temperature TF-R of the ferroelectric-relaxor phase transition was gradually shifted toward lower temperatures. In addition, the depolarization temperature Td gradually decreased from 125 to 53 °C. In the BNT-6BT-0.025Pr ceramics, giant electric field-induced strain (Smax) and normalized piezoelectric coefficient (d33*) were obtained (Smax = 0.58%, d33* = 723 pm/V). Furthermore, a significant photoluminescence emission intensity was achieved, exhibiting a bright red color. Due to significant enhancement of the piezoelectric and the photoluminescence properties, the BNT-6BT-0.025Pr ceramics exhibited strong competitiveness in actuators and multifunctional devices, which may broaden their application fields.

Phases study for AgNb(Ta,W)O3 lead-free antiferroelectric ceramics

Uncovering lead-free materials with an exceptionally high recoverable energy density is vital for the creation of future pulse power capacitors. This study determined that introducing Tungsten (W) and Tantalum (Ta) into the Nb-site of AgNbO3 lead-free antiferroelectric ceramics, while offsetting this with vacancies at the Ag-site, can effectively maintain the electrical homogeneity. Additionally, employing this co-doping approach can secure the antiferroelectric phases by lowering the necessary temperatures for M1-M2 and M2-M3 phase transitions. This may prove advantageous in the creation of novel AgNbO3-based energy storage ceramics. The use of in-situ high-resolution synchrotron powder x-ray diffraction (SPXD) at varying temperatures revealed for the first time that in 10 at% W doped AgNbO3, the M1 and M2 phases in the temperature range of −193 to ∼150 °C are more appropriately fitted as the non-polar Pbcm space group, whereas the M3 phase aligns with the mixed of non-polar Pbcm and polar Pmc21 space groups.

Significant improvement in energy storage for BT ceramics via NBT composition regulation

Dielectric ceramic capacitors play an important part in modern electronics, but the adoption of environmentally friendly lead-free ceramics is often limited by their inferior energy storage efficiency (η) and density (Wrec). One novel ceramic composition, (1-x)(Ba0.7Sr0.3)(Zr0.2Ti0.8)O3-xNa0.5Bi0.5TiO3 (BSZT-NBT, x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) was designed to achieve large max polarization (Pmax) and outstanding energy storage performance (ESP). Structural analyses indicate that BSZT-NBT ceramics form stable perovskite solid solutions. Dielectric properties testing confirms the enhanced relaxor behavior. Remarkably, the BSZT-NBT (x = 0.5) ceramics exhibit superb ESP, including ultrahigh η of 94.9%, elevated Wrec of 4.45 J·cm–3, large Pmax of 38.01 μC·cm–2. Furthermore, these ceramics demonstrate excellent temperature and frequency stability for ESP. Charge-discharge performance at room temperature and 120 kV·cm–1 showcases excellent Wdis, t0.9 and PD of 0.64 J·cm–3, 69.8 ns and 48 MW·cm–3, respectively. Our results indicate that the introduction of NBT effectively improves the Pmax and ESP of BT-based ceramics. The BSZT-NBT ceramics hold promise for addressing the limitations of lead-free ceramic capacitors and advancing their practical applications in electronic devices.

High energy storage characteristics for Ba0.9Sr0.1TiO3 (BST) doped Na0.7Bi0.1NbO3 (NBN) ceramics

In recent years, lead-free energy storage ceramics have been widely used as a new type of energy storage material with great application prospects. In this study, a modified NaNbO3 (NN) based ceramic, Na0.7Bi0.1NbO3 (NBN), is used as the matrix, and Ba0.9Sr0.1TiO3 (BST) is added as a doping agent. A series of (1-x)Na0.7Bi0.1NbO3-xBa0.9Sr0.1TiO3 (xBST, x = 0.1, 0.2, 0.3, 0.4) solid solutions have been designed and prepared using the solid-phase sintering method. The breakdown field strength (Eb) of 0.3BST ceramics reached 445 kV/cm, an unexpectedly ultra-high energy storage density (W) of 4.48 J/cm3 and a recoverable energy density (Wrec) of 3.47 J/cm3. In terms of charging and discharging performance, the ceramics have a low charging and discharging time of t0.9 = 1.38 μs. In addition, 0.1BST exhibits a high energy conversion efficiency of η = 87.35 %. These results confirm that (1-x)NBN-xBST ceramics are promising energy storage materials.

Achieving high energy storage performance and efficiency in lead-free SrTiO3 ceramics via neodymium and lithium co-doping technique

ABSTRACT There is an immediate demand for eco-friendly, high-performance, and highly stable energy storage materials for pulse power systems. Ceramics based on SrTiO3 have a high breakdown strength (BDS) and dielectric constant. In this work, we fabricated a polycrystalline of Sr(1-x)(Nd, Li)xTiO3 ceramics via microwave-assisted heating of the starting materials. X-ray diffraction analysis reveals a pure perovskite phase without any secondary phase. Scanning electron microscopy images exhibit dense grain morphology with a decrease in grain size as the dopant concentration increases. The frequency dependences of the dielectric properties were studied in the frequency range of 100 Hz-1 MHz at room temperature. The polarization-electric field hysteresis loops were examined to ascertain the effect of co-doping on the energy-storage capability of SrTiO3 ceramics. After increasing the co-dopants from 0 to 8%, the energy density increased nine times (from 0.11 J/cm3 to 0.952 J/cm3), and the energy storage efficiency increased from 80.71% to 95.98%, respectively. In addition, the samples demonstrate excellent thermal stability, and their energy storage properties are stable up to 80°C. We may infer from this discovery that the bulk Nd3+ and Li+ co-doped SrTiO3 materials are good candidates for high-energy-density capacitor applications.