Core–shell structured Bi0.5Na0.5TiO3KTaO3 + x% (in mass) Li2CO3 ceramics were fabricated in this study. Increasing x from 0 to 2 leads to the decrease of sintering temperature from 1 175 ℃ to 1 020 ℃. The limited diffusion of Ta5+ results in chemical heterogeneities and core–shell microstructures. The Ta5+-depleted cores show the nanodomains (~10 nm), while the Ta5+-rich shells display the polar nanoregions (1–2 nm). From x = 0 to 1, the appearance of cores with nanodomains contributes to the increase of dielectric constant and maximum polarization, while the further addition of Li2CO3 suppresses the dielectric and polarization responses due to the reduced grain sizes and polarization coupling. The enhanced dielectric relaxation and existence of core-shell microstructure with different polarization levels help to optimize the dielectric temperature stability. The x = 2 ceramics exhibit a stable high dielectric constant ~1 400 over a wide temperature range of 20–520 ℃. More encouragingly, the ultrafine grain size and core–shell microstructure in the x = 2 ceramics greatly benefit the improvement of breakdown strength. Combined with the delayed polarization saturation and high ergodicity, a high recoverable energy density of ~5.07 J/cm3 is obtained under 44 kV/mm, with a high efficiency of ~85.17%.
Yang L, Kong X, Li F, Hao H, Cheng Z, Liu H, et al. Perovskite lead-free dielectrics for energy storage applications. Prog Mater Sci 2019 10272–108. https://doi.org/10.1016/j.pmatsci.2018.12.005.
Hippel A v. Ferroelectricity, domain structure, and phase transitions of barium titanate. Rev Mod Phys 1950:22221–36. https://doi.org/10.1103/RevModPhys.22.221.
Suchanicz J. Investigations of the phase transitions in Na0.5Bi0.5TiO3. Ferroelectrics 1995;172(1):455–8. https://doi.org/10.1080/00150199508018512.
Zhang L, Cao S, Li Y, Jing R, Hu Q, Tian Y, et al. Achieving ultrahigh energy storage performance over a broad temperature range in (Bi0.5Na0.5)TiO3-based eco-friendly relaxor ferroelectric ceramics via multiple engineering processes. J Alloys Compd 2022:896163139. https://doi.org/10.1016/j.jallcom.2021.163139.
Zhou S, Pu Y, Zhao X, Ouyang T, Ji J, Zhang Q, et al. Dielectric temperature stability and energy storage performance of NBT-based ceramics by introducing high-entropy oxide. J Am Ceram Soc 2022;105(7):4796–4804. https://doi.org/10.1111/jace.18455.
Jiang Z, Yang Z, Yuan Y, Tang B, Zhang S. High energy storage properties and dielectric temperature stability of (1-x)(0.8Bi0.5Na0.5TiO3-0.2Ba0.3Sr0.7TiO3)-xNaNbO3 lead-free ceramics. J Alloys Compd 2021:851156821. https://doi.org/10.1016/j.jallcom.2020.156821.
Zhu C, Cai Z, Guo L, Jiang Y, Li L, Wang X. Simultaneously achieved ultrastable dielectric and energy storage properties in lead-free Bi0.5Na0.5TiO3-based ceramics. ACS Appl Energy Mater 2022;5(2):1560–70. https://doi.org/10.1021/acsaem.1c02964.
Xu Q, Song Z, Tang W, Hao H, Zhang L, Appiah M, et al. Ultra-wide temperature stable dielectrics based on Bi0.5Na0.5TiO3-NaNbO3 system. J Am Ceram Soc 2015;98(10):3119–26. https://doi.org/10.1111/jace.13693.
Schulz T, Veerapandiyan V, Deluca M, Töpfer J. Synthesis and properties of lead-free BNT-BT-xCZ ceramics as high-temperature dielectrics. Mater Res Bull 2022;145. https://doi.org/10.1016/j.materresbull.2021.111560.
Li F, Zhai J, Shen B, Zeng H. Recent progress of ecofriendly perovskite-type dielectric ceramics for energy storage applications. J. Adv. Dielectr. 2019 08(06). https://doi.org/10.1142/s2010135x18300050.
Huang Y, Li F, Hao H, Xia F, Liu H, Zhang S. Bi0.51Na0.47)TiO3 based lead free ceramics with high energy density and efficiency. J. Materiomics. 2019:5385–95. https://doi.org/10.1016/j.jmat.2019.03.006.
Li D, Shen Z-Y, Li Z, Luo W, Song F, Wang X, et al. Optimization of polarization behavior in (1 - x)BSBNT–xNN ceramics for pulsed power capacitors. J Mater Chem C 2020. https://doi.org/10.1039/D0TC01699C.
Qi H, Zuo R. Linear-like lead-free relaxor antiferroelectric (Bi0.5Na0.5)TiO3–NaNbO3 with giant energy-storage density/efficiency and super stability against temperature and frequency. J Mater Chem 2019;7(8):3971–8. https://doi.org/10.1039/c8ta12232f.
Qi H, Zuo R, Xie A, Tian A, Fu J, Zhang Y, et al. Ultrahigh energy-storage density in NaNbO3-based lead-free relaxor antiferroelectric ceramics with nanoscale domains. Adv Funct Mater 2019;29(35):1903877. https://doi.org/10.1002/adfm.201903877.
Li J, Shen Z, Chen X, Yang S, Zhou W, Wang M, et al. Grain-orientation-engineered multilayer ceramic capacitors for energy storage applications. Nat Mater 2020;19(9):999–1005. https://doi.org/10.1038/s41563–020-0704-x.
Li J, Li F, Xu Z, Zhang S. Multilayer lead-free ceramic capacitors with ultrahigh energy density and efficiency. Adv. Mater 2018;30(32):e1802155. https://doi.org/10.1002/adma.201802155.
Li M, Zhu M, Zheng M, Hou Y, Wang J, Chao X, et al. Excellent energy storage and discharge performances in Na1/2Bi1/2TiO3-based ergodic relaxors by enlarging the [AO12] cages. J Mater Chem C 2022:8845–53. https://doi.org/10.1039/d2tc00812b.
Ji H, Wang D, Bao W, Lu Z, Wang G, Yang H, et al. Ultrahigh energy density in short-range tilted NBT-based lead-free multilayer ceramic capacitors by nanodomain percolation. Energy Storage Mater 2021:38113–20. https://doi.org/10.1016/j.ensm.2021.01.023.
Fan P, Zhang Y, Zhang S-T, Xie B, Zhu Y, Marwat MA, et al. Low-temperature sintered (Na1/2Bi1/2)TiO3-based incipient piezoceramics for co-fired multilayer actuator application. J. Materiomics. 2019;5(3):480–8. https://doi.org/10.1016/j.jmat.2019.01.004.
Mishra A, Majumdar B, Ranjan R. A complex lead-free (Na, Bi, Ba)(Ti, Fe)O3 single phase perovskite ceramic with a high energy-density and high discharge-efficiency for solid state capacitor applications. J Eur Ceram Soc 2017;37(6):2379–84. https://doi.org/10.1016/j.jeurceramsoc.2017.01.036.
Pu Y, Zhang L, Cui Y, Chen M. High energy storage density and optical transparency of microwave sintered homogeneous (Na0.5Bi0.5)(1-x)BaxTi(1-x)SnyO3 ceramics. ACS Sustainable Chem Eng 2018;6(5):6102–9. https://doi.org/10.1021/acssuschemeng.7b04754.
Pu Y, Zhang L, Yao M, Ge W, Chen M. Improved energy storage properties of microwave sintered 0.475BNT-0.525BCTZ-xwt%MgO ceramics. Mater Lett 2017:189232–35. https://doi.org/10.1016/j.matlet.2016.12.020.
Li F, Hou X, Wang J, Zeng H, Shen B, Zhai J. Structure-design strategy of 0–3 type (Bi0.32Sr0.42Na0.20)TiO3/MgO composite to boost energy storage density, efficiency and charge-discharge performance. J Eur Ceram Soc 2019;39(9):2889–98. https://doi.org/10.1016/j.jeurceramsoc.2019.03.047.
Wen H, Wang X, Gui Z, Li L. Modeling of the core-shell microstructure of temperature-stable BaTiO3 based dielectrics for multilayer ceramic capacitors. J Electroceram 2007;21(1–4):545–8. https://doi.org/10.1007/s10832–007-9240–1.
Chazono H, Kishi H. Sintering characteristics in BaTiO3 Nb2O5 Co3O4 ternary system: Ⅰ, electrical properties and microstructure. J Am Ceram Soc 2004;82(10):2689–97. https://doi.org/10.1111/j.1151–2916.1999.tb02143.x.
Chazono H, Kishi H. Sintering characteristics in the BaTiO3 Nb2O5 Co3O4 ternary system: Ⅱ, stability of so-called “core–shell” structure. J Am Ceram Soc 2008;83101–06. https://doi.org/10.1111/j.1151–2916.2000.tb01155.x.
Chen C, Hao H, Cui J, Yu C, Tang Y, Cao M, et al. The role of diffusion behavior on the formation and evolution of the core-shell structure in BaTiO3-based ceramics. J Am Ceram Soc 2019;103(1):304–14. https://doi.org/10.1111/jace.16735.
Pathumarak S, Alkhafaji M, Lee W. Microstructural development on firing Nb2O5 and Bi2O3 doped BaTiO3. Br Ceram Trans 1994;93(3):114–8.
Zhigang Z, Weilong Z, Yugong W, Ruitao Z. Grain core-grain shell structure in ceramic-ceramic dielectrics. Ferroelectrics 1990;101(1):55–60. https://doi.org/10.1080/00150199008016500.
Gong H, Wang X, Zhang S, Yang X, Li L. Influence of sintering temperature on core-shell structure evolution and reliability in Dy modified BaTiO3dielectric ceramics. Phys. Status Solidi A-Appl. Mat. 2014;211(5):1213–8. https://doi.org/10.1002/pssa.201400013.
Xue G, Zhou X, Yan Z, Liu G, Luo H, Zhang D. Temperature-stable Na0.5Bi0.5TiO3-based relaxor ceramics with high permittivity and large energy density under low electric fields. J Alloys Compd 2021:882160755. https://doi.org/10.1016/j.jallcom.2021.160755.
Chung T-H, Sun H, Wen R, Kwok KW. Low-temperature-sintered Bi0.5Na0.5TiO3-based lead-free ferroelectric ceramics with good piezoelectric properties. Ceram Int 2018;44(4):4027–32. https://doi.org/10.1016/j.ceramint.2017.11.198.
Levi RD, Tsur Y. The effect of oxygen vacancies in the early stages of BaTiO3 nanopowder sintering. Adv. Mater 2005;17(13):1606–8. https://doi.org/10.1002/adma.200401859.
Shi J, Liu X, Zhu F, Tian W, Xia Y, Li T, et al. Oxygen vacancy migration and its lattice structural origin in A-site non-stoichiometric bismuth sodium titanate perovskites. J. Materiomics. 2022;8(3):719–29. https://doi.org/10.1016/j.jmat.2021.09.008.
Aksel E, Forrester JS, Kowalski B, Jones JL, Thomas PA. Phase transition sequence in sodium bismuth titanate observed using high-resolution x-ray diffraction. Appl Phys Lett 2011;99(22):222901. https://doi.org/10.1063/1.3664393.
Kimura T, Dong Q, Yin S, Hashimoto T, Sasaki A, Sato T. Synthesis and piezoelectric properties of Li-doped BaTiO3 by a solvothermal approach. J Eur Ceram Soc 2013;33(5):1009–15. https://doi.org/10.1016/j.jeurceramsoc.2012.11.007.
Lei N, Zhu M, Yang P, Wang L, Wang L, Hou Y, et al. Effect of lattice occupation behavior of Li+ cations on microstructure and electrical properties of (Bi1/2Na1/2)TiO3-based lead-free piezoceramics. J Appl Phys 2011;109(5):054102. https://doi.org/10.1063/1.3555598.
Shannon RD, Fischer RX. Empirical electronic polarizabilities in oxides, hydroxides, oxyfluorides, and oxychlorides. Phys Rev B 2006;73(23):235111. https://doi.org/10.1103/PhysRevB.73.235111.
Wylie-Van Eerd B, Damjanovic D, Klein N, Setter N, Trodahl J. Structural complexity of (Na0.5Bi0.5)TiO3-BaTiO3 as revealed by Raman spectroscopy. Phys Rev B 2010;82(10):104112. https://doi.org/10.1103/PhysRevB.82.104112.
Roukos R, Dargham SA, Romanos J, Chaumont D. Detection of morphotropic phase boundary in A-site/Ca-substituted Na0.5Bi0.5TiO3 complex oxides ferroelectric system. J Alloys Compd 2020:840. https://doi.org/10.1016/j.jallcom.2020.155509.
Choi S-Y, Jeong S-J, Lee D-S, Kim M-S, Lee J-S, Cho JH, et al. Gigantic electrostrain in duplex structured alkaline niobates. Chem Mater 2012;24(17):3363–9. https://doi.org/10.1021/cm301324h.
Zhou X, Qi H, Yan Z, Xue G, Luo H, Zhang D. Superior thermal stability of high energy density and power density in domain-engineered Bi0.5Na0.5TiO3-NaTaO3 relaxor ferroelectrics. ACS Appl Mater Interfaces 2019;11(46):43107–15. https://doi.org/10.1021/acsami.9b13215.
Wang Z, Kang R, Liu W, Zhang L, He L, Zhao S, et al. Bi0.5Na0.5)TiO3-based relaxor ferroelectrics with medium permittivity featuring enhanced energy-storage density and excellent thermal stability. Chem Eng J 2022;427. https://doi.org/10.1016/j.cej.2021.131989.
Acosta M, Schmitt LA, Molina-Luna L, Scherrer MC, Brilz M, Webber KG, et al. Core-shell lead-free piezoelectric ceramics: current status and advanced characterization of the Bi1/2Na1/2TiO3-SrTiO3 system. J Am Ceram Soc 2015;98(11):3405–22. https://doi.org/10.1111/jace.13853.
Koruza J, Rojas V, Molina-Luna L, Kunz U, Duerrschnabel M, Kleebe H-J, et al. Formation of the core–shell microstructure in lead-free Bi1/2Na1/2TiO3-SrTiO3 piezoceramics and its influence on the electromechanical properties. J Eur Ceram Soc 2016;36(4):1009–16. https://doi.org/10.1016/j.jeurceramsoc.2015.11.046.
Axelsson A-K, Pan Y, Valant M, Alford N. Synthesis, sintering, and microwave dielectric properties of KTaO3Ceramics. J Am Ceram Soc 2009;92(8):1773–8. https://doi.org/10.1111/j.1551–2916.2009.03130.x.
Ma C, Tan X, Dul'kin E, Roth M. Domain structure-dielectric property relationship in lead-free (1−x)(Bi1/2Na1/2)TiO3-xBaTiO3 ceramics. J Appl Phys 2010;108(10):104105. https://doi.org/10.1063/1.3514093.
Fan Z, Yu Y, Huang J, Zhang Q, Lu Y, He Y. Excellent energy storage properties over a wide temperature range under low driving electric fields in NBT-BSN lead-free relaxor ferroelectric ceramics. Ceram Int 2021;47(4):4715–21. https://doi.org/10.1016/j.ceramint.2020.10.040.
Wu J, Zhang H, Meng N, Koval V, Mahajan A, Gao Z, et al. Perovskite Bi0.5Na0.5TiO3-based materials for dielectric capacitors with ultrahigh thermal stability. Mater Des 2021:198109344. https://doi.org/10.1016/j.matdes.2020.109344.
Fu Y, Hou Y, Song B, Cheng H, Liu X, Yu X, et al. Construction of lead-free dielectrics for high temperature multilayer ceramic capacitors and its inner electrode matching characteristics. J Alloys Compd 2022:903163995. https://doi.org/10.1016/j.jallcom.2022.163995.
Zhu C, Cai Z, Luo B, Guo L, Li L, Wang X. High temperature lead-free BNT-based ceramics with stable energy storage and dielectric properties. J Mater Chem 2020;8(2):683–92. https://doi.org/10.1039/c9ta10347c.
Huang YH, Wu YJ, Liu B, Yang TN, Wang JJ, Li J, et al. From core–shell Ba0.4Sr0.6TiO3@SiO2 particles to dense ceramics with high energy storage performance by spark plasma sintering. J Mater Chem 2018;6(10):4477–84. https://doi.org/10.1039/c7ta10821d.
He J, Liu X, Zhao Y, Du H, Zhang T, Shi J. Dielectric stability and energy-storage performance of BNT-based relaxor ferroelectrics through Nb5+ and its excess modification. ACS Appl. Electron. Mater. 2022;4(2):735–43. https://doi.org/10.1021/acsaelm.1c01129.
Qiao X, Chao X, Yang Z. Bi0.5Na0.5TiO3-based ceramics with high energy storage density and good thermal stability. J Mater Sci Mater Electron 2021;33(4):2012–9. https://doi.org/10.1007/s10854–021-07404–1.
Wu L, Zhang J, Du H, Chen J, Yu H, Liu Y, et al. Chemical nature of the enhanced energy storage in A-site defect engineered Bi0.5Na0.5TiO3-based relaxor ferroelectrics. J Alloys Compd 2022:905164183. https://doi.org/10.1016/j.jallcom.2022.164183.
Jiang Z, Yuan Y, Yang H, Li E, Zhang S. Excellent thermal stability and energy storage properties of lead-free Bi0.5Na0.5TiO3-based ceramic. J Am Ceram Soc 2022;105(6):4027–38. https://doi.org/10.1111/jace.18332.
Li X, Dong X, Wang F, Tan Z, Zhang Q, Chen H, et al. Realizing excellent energy storage properties in Na0.5Bi0.5TiO3-based lead-free relaxor ferroelectrics. J Eur Ceram Soc 2022;42(5):2221–9. https://doi.org/10.1016/j.jeurceramsoc.2021.12.028.
Ma Z, Su Q, Zhu J, Meng X, Zhao Y, Xin G, et al. Optimization of energy-storage properties for lead-free relaxor-ferroelectric (1-x)Na0.5Bi0.5TiO3-xSr0.7Nd0.2TiO3 ceramics. J Mater Sci 2022;57(1):217–28. https://doi.org/10.1007/s10853–021-06684–6.
Shen Y, Wu L, Zhao J, Liu J, Tang L, Chen X, et al. Constructing novel binary Bi0.5Na0.5TiO3-based composite ceramics for excellent energy storage performances via defect engineering. Chem Eng J 2022:439135762. https://doi.org/10.1016/j.cej.2022.135762.
Jiao Y, Song S, Chen F, Zeng X, Wang X, Song C, et al. Energy storage performance of 0.55Bi0.5Na0.5TiO3-0.45SrTiO3 ceramics doped with lanthanide elements (Ln = La, Nd, Dy, Sm) using a viscous polymer processing route. Ceram Int 2022;48(8):10885–94. https://doi.org/10.1016/j.ceramint.2021.12.305.
Chen L, Deng S, Liu H, Wu J, Qi H, Chen J. Giant energy-storage density with ultrahigh efficiency in lead-free relaxors via high-entropy design. Nat Commun 2022;13(1):3089. https://doi.org/10.1038/s41467–022-30821–7.
Banerjee K, Alvi SB, Rengan AK, Asthana S. Investigation on the discharge energy storage density of the Rb substituted Na0.5Bi0.5TiO3 relaxor ferroelectric and its suitability for the orthopedic application. J Am Ceram Soc 2019;102(11):6802–16. https://doi.org/10.1111/jace.16596.
Jaita P, Lertcumfu N, Rujijanagul G. Temperature dependence on ferroelectric, energy storage density, and electric field-induced strain response of lead-free Bi0.485(Na0.388K0.097). Ba 2019;201(1):142–54. https://doi.org/10.1080/10584587.2019.1668698.
Xing J, Huang Y, Xu Q, Wu B, Zhang Q, Tan Z, et al. Realizing high comprehensive energy storage and ultrahigh hardness in lead-free ceramics. ACS Appl Mater Interfaces 2021;13(24):28472–83. https://doi.org/10.1021/acsami.1c05153.
Yang Z, Gao F, Du H, Jin L, Yan L, Hu Q, et al. Grain size engineered lead-free ceramics with both large energy storage density and ultrahigh mechanical properties. Nano Energy 2019:58768–77. https://doi.org/10.1016/j.nanoen.2019.02.003.
Dong X, Li X, Chen H, Dong Q, Wang J, Wang X, et al. Realizing enhanced energy storage and hardness performances in 0.90NaNbO3−0.10Bi(Zn0.5Sn0.5)O3 ceramics. J. Adv. Ceram. 2022;11(5):729–41. https://doi.org/10.1007/s40145–022-0566–6.
Zuo C, Yang S, Cao Z, Yu H, Wei X. Excellent energy storage and hardness performance of Sr0.7Bi0.2TiO3 ceramics fabricated by solution combustion-synthesized nanopowders. Chem Eng J 2022:442136330. https://doi.org/10.1016/j.cej.2022.136330.