Properties of ZnNb2O6 Doped BNT-Based Lead-Free Relaxor Ferroelectric Ceramics
In this paper,0.7(Na0.5Bi0.5)TiO3-0.3(Sr0.7Bi0.2)TiO3-xZnNb2O6(abbreviated as BNT-SBT-xZN,where x=0.5％,1.0％,1.5％and 2.0％,molar fraction)ceramics were prepared by the solid-state reaction method.The effect of ZnNb2O6 doping on the structure and properties of BNT-based ceramic materials was studied.The results show that,BNT-SBT-xZN ceramics doped with a small amount of ZnNb2O6(x=0.5％)have pure perovskite structure with compact microstructure and no second phase.At room temperature,they are typical relaxor ferroelectrics(dispersion index y＞1.7).For all unpoled and poled BNT-SBT-xZN ceramics of x=0.5％,the transition temperature of ferroelectric-relaxation(TR-E)is lower than room temperature,while TR-E is below 100℃,which denotes the dielectric anomalous associated with thermal relaxation of polar nano regions(PNRs)in rhombohedral(R3c)and tetragonal(P4bm)symmetrical structure.When the content of ZnNb2O6 increases,the ergodic relaxor state gradually plays a dominant role,maximum polarization(Pmax)and remanent polarization(Pr)both show a decreasing trend.BNT-SBT-xZN ceramics with x=0.5％have high Pmax,low Pr and large △P,resulting in excellent energy storage characteristics and frequency and temperature stability with Pmax of 44.7 μC/cm2,Pr of 12.4 pC/cm2,△P of 32.3 µC/cm2,energy density(W1)of 1.066 J/cm3,energy storage efficiency(η)of 48.68％under 110 kV/cm.Moreover,discharge energy density Wd,maximum discharge current Imax,current density CD and power density PD of 0.60 J/cm3,45.33 A,1 443 A/cm2 and 72.2 MW/cm3 are obtained at room temperature and 100 kV/cm,respectively.
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