Preparation And Properties Of Sodium Niobate Based Energy Storage Ceramic Materials

In recent years,the continuous consumption of traditional fossil energy materials makes the energy crisis more and more serious.It is urgent to accelerate research and development of environmentally friendly,low-cost renewable energy.Compared with batteries and electrochemical capacitors,ceramic dielectric capacitors have the advantages of fast charge-discharge rate and high dielectric constant.However,the most widely used energy storage ceramics are toxic lead-based ceramics.There is an urgent need to replace the environmentally hazardous lead-based ceramics by researching more environmentally safe lead-free ceramics.In the current lead-free ceramic systems,sodium niobate lead-free antiferroelectric ceramics have wide band gap,wide sintering temperature,high polarization strength and low cost,so that they have great potential in energy storage applications.This thesis focuses on the modification of sodium niobate based ceramics,and their dielectric,ferroelectric and charge-discharge properties were studied and analyzed.The(1-x)NaNbO3-x(Sr0.85Bi0.1)(Mg1/3Nb2/3)O3(x=0,0.05,0.10,0.15,0.20)lead-free ceramics(abbreviated as(1-x)NN-xSBMN)were prepared by the traditional solid phase method.The doping of SBMN significantly reduced the grain size of the system.The breakdown strength of the samples is increased.When the applied electric field reaches 420 kV/cm,the 0.90NN-0.10SBMN energy storage ceramic can achieve an excellent effective energy storage density(Wrec)of 2.43 J/cm3 and high energy storage efficiency(η)of 68.3%.Meanwhile,the ceramic has excellent temperature and frequency stability.In addition,0.90NN-0.10SBMN ceramic demonstrates super-fast charge-discharge rate(t0.9=52.0 ns)and excellent power density of 36.23 MW/cm3 in charge-discharge tests.The(1-x)NaNbO3-x(Bi0.5La0.5)(Mg2/3Ta1/3)O3(x=0,0.06,0.08,0.10,0.12)lead-free energy storage ceramics(abbreviated as(1-x)NN-xBLMT)were prepared by the traditional solid phase method.The introduction of(Bi0.5La0.5)3+and(Mg2/3Ta1/3)3+into the A-site and B-site of NN ceramic can cause lattice distortion,destroy the long-range ferroelectric order,inhibit the residual polarization(Pr)of the system,reduce the average grain size,and obtain excellent Wrec and η.The 0.90NN-0.10BLMT ceramic exhibits excellent Wrec(3.69 J/cm3)and η(78%)at 440 kV/cm.In the charge-discharge test,the 0.90NN-0.10BLMT ceramic exhibits a super-fast charge-discharge rate(t0.9=23.6 ns)at room temperature.The(Na1-3/2xBi3/2x)(Nb1-xNix)O3(x=0,0.05,0.10,0.15,0.20)energy storage ceramics(abbreviated as NBNNx)were prepared by traditional solid phase method.The addition of Bi3+a nd Ni2+ can effectively reduce the sintering temperature of NN ceramic and prevent the volatilization of Na+ at high temperature.The hybridization of 6p orbitals of Bi3+and 2p orbitals of O2-is conducive to the promotion of maximum polarization intensity(Pmax).Meanwhile,doping non-homogeneous Ni2+ at B-site with low average electronegativity can form a random local field,which can strengthen the ionic bond,destroy the internal long-range order,and reduce Pr.The best component NBNN0.10 ceramic obtains an excellent Wrec(3.42 J/cm3)and a high η(78.2%)at 360 kV/cm.In addition,the dielectric temperature spectra show that the system has obvious relaxor characteristics.Under the electric field of 200 kV/cm,the variation rate of Wrec of NBNN0.10 ceramic at different temperatures and frequencies is less than 4%,showing excellent temperature stability and frequency stability.(1-x)NaNbO3-x(Bi0.7Sm0.3)(Ni0.5Zr0.5)O3(x=0,0.04,0.07,0.10,0.13)lead-free energy storage ceramics(abbreviated as(1-x)NN-xBSNZ)were prepared by introducing Sm3+and Zr4+on the basis of doping Bi3+and Ni2+with NN ceramic.The addition of Sm3+and Zr4+ helps to reduce the grain size,enhance the relaxor behavior of the system,thus improving the energy storage performance of the ceramics.Ferroelectric test shows that 0.90NN-0.10BSNZ ceramic can obtain a super high Wrec(4.16 J/cm3)and an excellent η(88.38%)at the high electric field of 440 kV/cm.In addition,in the charge-discharge test of 0.90NN-0.10BSNZ ceramic,the super-fast charge-discharge rate(t0.9=24.6 ns)is obtained at room temperature,and can remain stable at high temperature,and the power density is 19.58 MW/cm3.