Preparation And Energy Storage Behavior Of Rare Earth-Doped Sodium Bismuth Titanate-Based Relaxor Ferroelectric Ceramics

In face of increasingly serious environmental pollution and energy crisis,it is imperative to develop new environmentally friendly energy materials.Among many energy storage devices,lead-free energy storage ceramic capacitors have been widely used in the field of pulsed power electronics due to their high-power density,fast charge/discharge speed,and long service life.However,the low energy-storage density and energy-storage efficiency of ceramic capacitors seriously hinder their practical application.Therefore,it is of great significance to develop ceramic capacitors with high energy-storage density and energy-storage efficiency to promote the development of the energy-storage field.This work takes sodium bismuth titanate-based(Na_0.5Bi_0.5Ti O₃)ferroelectric materials as the research object,and uses the tape-casting method to prepare ceramic materials with uniform and dense structure.This work systematically studies the microstructure,dielectric response,relaxation behavior,energy-storage characteristics and charge-discharge performance of the ceramics,with the aim of obtaining excellent energy-storage ceramic design methods and energy-storage performance optimization strategies.Sm³⁺-doped Na_0.5Bi_0.5Ti O₃-Sr Ti O₃（abbreviated as NBT-ST）lead-free relaxor ferroelectric ceramics with high energy-storage density and good charge-discharge performance were successfully prepared.The structural synergistic enhancement effect is achieved by introducing rare earth Sm³⁺into NBT-ST ceramics.The introduction of rare earth Sm³⁺not only reduces the grain size of ceramics,but also regulates the domain structure of ceramics,which improves the breakdown strength and relaxation properties of ceramics.When the doping amount of Sm³⁺was 0.2 mol,the NBT-SST lead-free relaxor ferroelectric ceramics obtained a recoverable energy-storage density of 3.81 J/cm³ and an energy-storage efficiency of 84.7%.At the same time,NBT-SST ceramics also have a power density of 135 MW/cm³ and a discharge speed of 89 ns.In the resistance-inductance-capacitance（R-L-C）loop,this component ceramic has a maximum discharge energy density of 2.08 J/cm³.Based on composition design and grain size engineering,we introduce the third component La(Mg_2/3Nb_1/3)O₃（LMN）on the basis of NBT-SST relaxor ferroelectric ceramics for modification.It is found that the introduction of LMN refines the grain size of NBT-SST ceramics,improves the leakage and dielectric properties,and leads to the improvement of the breakdown strength.When the LMN doping ratio is 0.03,the NBT-SST-LMN ceramic achieves a recoverable energy-storage density of 5.94 J/cm³ and an energy-storage efficiency of 86.9%.Meanwhile,NBT-SST-LMN ceramics also possess a huge current density of 1452A/cm² and a power density of 275 MW/cm³.Moreover,NBT-SST-LMN ceramics obtained a discharge speed of 65 ns and a discharge energy density of 3.9 J/cm³ under the electric field strength of 380 k V/cm.The 0.97（NBT-SST）-0.03LMN multilayer ceramic capacitor（MLCC）was prepared by using the excellent energy-storage performance of NBT-SST-LMN ceramics.This capacitor achieves a recoverable energy-storage density of 10.1 J/cm³ and an energy-storage efficiency of 81.4%under the electric field strength of 780 k V/cm.To sum up,this work introduces the strategy of introducing the third component LMN on the basis of NBT-SST,and obtains a lead-free ceramic capacitor with high recoverable energy-storage density and energy-storage efficiency,which is expected to play an important role in the field of pulse power electronics.