Multilayer Lead‐Free Ceramic Capacitors with Ultrahigh Energy Density and Efficiency

Abstract

The utilization of antiferroelectric (AFE) materials is thought to be an effective approach to enhance the energy density of dielectric capacitors. However, the high energy dissipation and inferior reliability that are associated with the antiferroelectric-ferroelectric phase transition are the main issues that restrict the applications of antiferroelectric ceramics. Here, simultaneously achieving high energy density and efficiency in a dielectric ceramic is proposed by combining antiferroelectric and relaxor features. Based on this concept, a lead-free dielectric (Na Bi )TiO -x(Sr Bi )TiO (NBT-xSBT) system is investigated and the corresponding multilayer ceramic capacitors (MLCCs) are fabricated. A record-high energy density of 9.5 J cm , together with a high energy efficiency of 92%, is achieved in NBT-0.45SBT multilayer ceramic capacitors, which consist of ten dielectric layers with the single-layer thickness of 20 µm and the internal electrode area of 6.25 mm . Furthermore, the newly developed capacitor exhibits a wide temperature usage range of -60 to 120 °C, with an energy-density variation of less than 10%, and satisfactory cycling reliability, with degradation of less than 8% over 10 cycles. These characteristics demonstrate that the NBT-0.45SBT multilayer ceramic is a promising candidate for high-power energy storage applications.

Bi0.5K0.5TiO3–CaTiO3 ceramics: Appearance of the pseudocubic structure and ferroelectric‐relaxor transition characters

“…The thin double ferroelectric hysteresis loops have been reported in Bi 0.5 Na 0.5 TiO 3 ‐based, (Pb,La)(Zr,Ti)O 3 , and BiMeO 3 –BaTiO 3 (eg, Bi(Ti 1/2 Mg 1/2 )O 3 –BaTiO 3 and Bi(Ti 1/2 Zn 1/2 )O 3 –BaTiO 3 ) solid solution systems . It could be caused by the antiferroelectric relaxor characters or the field‐induced transition between PNRs and domains . There is no structural evidence for the antiferroelectric ordering, and we consider that the double ferroelectric hysteresis loops appearing in BKT‐CT should be related to field‐induced behaviors.…”

Bi‐modified SrTiO3‐based ceramics for high‐temperature energy storage applications

“…Moreover, SBT has been used as end member to form solid solution dielectrics for energy storage applications. A high energy density of 9.5 J/cm 3 together with a high energy efficiency of 92% at 720 kV/cm was achieved in 0.55(Na 0.5 Bi 0.5 )TiO 3 –0.45SBT solid solution multilayer ceramic capacitor . More recently, the 0.9SBT–0.1BiFeO 3 solid solution thin film was studied where a high energy density of 48.5 J/cm 3 but low energy efficiency of 48% was reported .…”

High‐recoverable energy‐storage density and dielectric tunability in Eu3+‐doped NBT‐xSTO binary solid solution films

“…A diffuse phase transition is generally characterized by: (a) broadening in the dielectric constant ( ε ) versus temperature ( T ) curve; (b) frequency dispersion of both dielectric constant and loss tangent in the transition region thereby implying a frequency dependence of T max ; (c) a relatively large separation (in temperature) between the maximum of the real (dielectric constant) and imaginary (dielectric loss) parts of the dielectric spectrum; (d) a deviation from Curie‐Weiss law in the vicinity of T max . The diffuseness was analyzed based on a modified Curie‐Weiss law given in the following formula:where C is a constant and γ is the degree of diffuseness: for a normal Curie‐Weiss law (FEs), γ is equal to 1; for a complete diffuse phase transition (relaxor), γ is equal to 2 . The slope of the linear fitting line of the data through ln(1/ ε − 1/ ε max ) ~ ln( T − T max ) is assigned to the value of parameter γ .…”

“…With increasing the temperature, NBT undergoes several electric behaviors such as ferroelectric (FE) (at room temperature), AFE‐like behavior (above 220°C), and RFE behavior (at ~320°C, T c ) . Since NBT exhibits both AFE and RFE characteristics, few chemical substitutions, such as BaTiO 3 (BTO), SrTiO 3 (STO) and (Bi 0.5 K 0.5 )TiO 3 (KBT), were used to form a solid solution with NBT to achieve relaxor behavior, which is hopeful to reduce the polarization hysteresis, and cause the increase in energy density and efficiency . A high energy storage density has been reported in NBT‐based ternary solid solution thin films, such as NBT‐KBT‐SrZrO 3 thin films (34.69 J cm −3 ) and NBT‐BTO‐BiFeO 3 thin films (42.9 J cm −3 ) .…”

“…Electrical energy storage devices, such as electrochemical capacitors, dielectric capacitors, and batteries, have been extensively investigated due to their wide applications in advanced electrical power systems. [1][2][3] Among these electrochemical energy storage devices, and dielectric capacitors play an important role in high-power applications because of their fast charge-discharge speed. 4,5 However, the energy density of dielectric ceramic capacitors is lower than that of electrochemical energy storage devices.…”