Enhanced DC-bias stability and reliability in BaTiO₃ Ceramics via B-site Ca doping induced long-range order disruption

Abstract

With the ongoing miniaturization of multilayer ceramic capacitors (MLCCs), there is an increasing demand for dielectric materials that simultaneously exhibit high dielectric constant, excellent DC-bias stability, and high reliability. To address this challenge, B-site Ca doping was employed to regulate the polar structure of BaTiO₃-based ceramics. In this study, we systematically investigated the effects of Ca doping on the crystal structure, defects, and microstructure by varying the dopant concentration and occupancy behavior. The B-site Ca-doped BaTiO₃ ceramics exhibit a pseudo-cubic structure, characterized by the coexistence of tetragonal and cubic phases. Ca²⁺ substitution for Ti⁴⁺ disrupts the long-range ferroelectric order, leading to the formation of polar nanoregions (PNRs) interconnected and embedded within a non-polar matrix. Defect analysis and studies on reducing atmosphere sintering reveal that oxygen vacancies are effectively localized by cation defects, thereby suppressing long-range conduction. These structural features synergistically result in a high dielectric constant, superior DC-bias stability, enhanced insulation resistance, and strong non-reducibility. This work provides fundamental insights into the microstructural design of BaTiO₃-based ceramics and highlights their potential for high-reliability MLCC applications.

Keywords

DC-bias stability / reliability / BaTiO₃ / Ca-doping

References

[1] Levin I,Woicik JC.Local-structure origins of the sustained Curie temperature in (Ba,Ca)TiO₃ ferroelectrics.Appl Phys Lett2013;102:162906

[2] Fu D,Koshihara SY,Tsuneyuki S.Anomalous phase diagram of ferroelectric (Ba,Ca)TiO₃ single crystals with giant electromechanical response.Phys Rev Lett2008;100:227601

[3] Hsiang H,Huang C.Dielectric properties of BaTiO₃ and Ba_0.95Ca_0.05TiO₃ sintered in a reducing atmosphere.Ceram Int2023;49:28751-7

[4] Yoon S,Kwon S.Resistance degradation behavior of Ca-doped BaTiO₃.J Mater Res2010;25:2135-42.[DOI:10.1557/JMR.2010.0278]

[5] Huang X,Wang P.Excellent permittivity-temperature stability and reliability performance of ultra-thin Ba_0.97Ca_0.03TiO₃ -based MLCCs.J Asian Ceram Soc2023;11:146-58

[6] Sakabe Y,Hiramatsu T.Dielectric properties of fine-grained BaTiO₃ ceramics doped with CaO.Jpn J Appl Phys2002;41:6922-5

[7] Sakabe Y.Nonreducible mechanism of {(Ba_{1- x}Ca_x)O}_mTiO₂ (m >1) ceramics.Jpn J Appl Phys2002;41:6461-5

[8] Zhang L,Feteira A.Comment on the use of calcium as a dopant in X8R BaTiO₃-based ceramics.Applied Physics Letters2007;90:142914

[9] Lee SJ,Han YH.Relaxation behavior of oxygen vacancy complexes in Ba(Ti_1-xCa_x)O_3-x.Mater Chem Phys2010;121:161-4

[10] Johnson KM.Variation of dielectric constant with voltage in ferroelectrics and its application to parametric devices.J Appl Phys1962;33:2826-31

[11] Hennings D,Simon G.Diffuse ferroelectric phase transitions in Ba(Ti_1-yZr_y)O₃ ceramics.J Am Ceram Soc1982;65:539-44

[12] Yoon S,Kim D.Influence of tetragonality (c/a) on dielectric nonlinearity and direct current (dc) bias characteristics of (1-x)BaTiO_3-xBi_0.5Na_0.5TiO₃ ceramics.J Appl Phys2017;122:154103

[13] Wen H,Chen R.Modeling of dielectric behaviors of multilayer ceramic capacitors under a direct current bias field.J Am Ceram Soc2006;89:550-6

[14] Zhang W,Xiao M.High DC-bias stability and reliability in BaTiO₃-based multilayer ceramic capacitors: the role of the core-shell structure and the electrode.ACS Appl Mater Interfaces2024;16:1158-69

[15] Zhu C,Guo L,Wang X.Grain size engineered high-performance nanograined BaTiO₃ -based ceramics: experimental and numerical prediction.J Am Ceram Soc2021;104:273-83

[16] Yuan Q,Cheng S.Bioinspired hierarchically structured all-inorganic nanocomposites with significantly improved capacitive performance.Adv Funct Mater2020;30:2000191

[17] Yang L,Cheng Z.Ultra-high energy storage performance with mitigated polarization saturation in lead-free relaxors.J Mater Chem A2019;7:8573-80

[18] Zhu M,Zhang H.Diffused phase transition boosted dye degradation with Ba (Zr_xTi_1-x)O₃ solid solutions through piezoelectric effect.Nano Energy2021;89:106474

[19] Ravel B.Athena, artemis, hephaestus: data analysis for X-ray absorption spectroscopy using IFEFFIT.J Synchrotron Radiat2005;12:537-41

[20] Kong LB,Zhang TS.Electrically tunable dielectric materials and strategies to improve their performances.Prog Mater Sci2010;55:840-93

[21] Krayzman V,Woicik JC,Nelson EJ.Ca K-edge X-ray absorption fine structure in BaTiO₃-CaTiO₃ solid solutions.J Appl Phys2013;113:044106

[22] Yang Y,Zhang L.Structure, electrical and dielectric properties of Ca substituted BaTiO₃ ceramics.Ceram Int2018;44:11109-15

[23] Hao X.A review on the dielectric materials for high energy-storage application.J Adv Dielect2013;03:1330001

[24] He Z,Tao Y.Anomalous dielectric nonlinearity in niobium and aluminum Co-doped SrTiO₃ ceramics with giant permittivity and low dielectric loss.J Phys Chem C2019;123:18142-9

[25] Randall CA,Reaney I,Trolier-mckinstry S.Antiferroelectrics: history, fundamentals, crystal chemistry, crystal structures, size effects, and applications.J Am Ceram Soc2021;104:3775-810

[26] Zhang L,Thakur OP.Ferroelectric aging and recoverable electrostrain in BaTi_0.98Ca_0.02O_2.98 ceramics.J Am Ceram Soc2008;91:3101-4

[27] Dobal PS,Katiyar RS,Guo R.Micro-Raman scattering and dielectric investigations of phase transition behavior in the BaTiO₃-BaZrO₃ system.J Appl Phys2001;89:8085-91

[28] Perry CH.Temperature dependence of the raman spectrum of BaTiO₃.Phys Rev Lett1965;15:700-2

[29] Zheng H,Quimby R.Raman spectroscopy of B-site order-disorder in CaTiO₃-based microwave ceramics.J Eur Ceram Soc2003;23:2653-9

[30] Siny I,Katiyar R,Bhalla A.Raman spectroscopy of Mg-Ta order-disorder in BaMg₁₃Ta₂₃O₃.J Phys Chem Solids1998;59:181-95

[31] Bersuker IB.Pseudo-Jahn-teller effect-a two-state paradigm in formation, deformation, and transformation of molecular systems and solids.Chem Rev2013;113:1351-90

[32] Bersuker IB.Pseudo Jahn-Teller origin of perovskite multiferroics, magnetic-ferroelectric crossover, and magnetoelectric effects: the d0-d10 problem.Phys Rev Lett2012;108:137202

[33] Asokan K,Chiou JW.Electronic structures of Ba_1-xCa_xTiO₃ studied by X-ray absorption spectroscopy and theoretical calculation.J Phys Condens Matter2001;13:11087-95

[34] Li C,Huang YH.Pinched P-E hysteresis loops in Ba₄Sm₂Fe_0.5Ti₃Nb_6.5O₃₀ ceramic with tungsten bronze structure.Appl Phys Lett2019;115:082901

[35] Takenaka H,Liu S.Slush-like polar structures in single-crystal relaxors.Nature2017;546:391-5

[36] Zhang M,Yang BB.Ultrahigh energy storage in high-entropy ceramic capacitors with polymorphic relaxor phase.Science2024;384:185-9

[37] Wei X.Nonlinear dielectric properties of barium strontium titanate ceramics.Mater Sci Eng B2003;99:74-8

[38] Dunbar TD,Tuttle BA,Tsur Y.Electron paramagnetic resonance investigations of lanthanide-doped barium titanate:  dopant site occupancy.J Phys Chem B2004;108:908-17

[39] Kolodiazhnyi T.Analysis of point defects in polycrystalline BaTiO₃ by electron paramagnetic resonance.J Phys Chem Solids2003;64:953-60

[40] Ward RE,Dean JS,Harding JH.Using metadynamics to obtain the free energy landscape for cation diffusion in functional ceramics: dopant distribution control in rare earth-doped BaTiO₃.Adv Funct Mater2020;30:1905077

[41] Erhart P.Modeling the electrical conductivity in BaTiO₃ on the basis of first-principles calculations.J Appl Phys2008;104:044315

[42] Ren X.Large electric-field-induced strain in ferroelectric crystals by point-defect-mediated reversible domain switching.Nat Mater2004;3:91-4

[43] Zulueta YA,Leyet Y,Anglada-rivera J.Influence of titanium and oxygen vacancies on the transport and conducting properties of barium titanate.Phys Status Solidi (b)2016;253:345-50