Study On Preparation And Energy Storage Performances Of Potassium Sodium Niobate Based Ceramics

In recent decades,the rapid development of human economic and life cannot be separated from the development of energy.From daily lighting and electricity,to military aerospace,people are consuming energy all the time.The development of energy also drives the development of all walks of life,and all kinds of energy storage devices have developed very rapidly in recent decades.As a kind of energy storage devices,ceramic capacitors are widely used in communication systems,integrated circuits and other fields due to their advantages of miniaturization,portability,high stability and long service time.Among them,Pb-based ceramics with ultrahigh energy storage density have attracted the attention of most researchers.However,with the development of environmental protection economy,Pb-based ceramics have gradually faded into the market due to their harmfulness,and then a research upsurge of lead-free energy storage ceramics has been attracted.However,the low performances of lead-free energy storage ceramics limit their development and application,so improving the performances of lead-free energy storage ceramics has become one of the current research hotspots.This paper focuses on the energy storage performances of potassium sodium niobate based ceramics,and other related properties were analyzed and discussed.1.(1-x)K0.5Na0.5NbO3-x(Sr0.2Bi0.8)(Mg0.6Ta0.4)O3(short for(1-x)KNNxSBMT)lead-free energy storage ceramics were prepared by the traditional solidstate method.According to various analyses,the addition of SBMT breaks the original ferroelectric long-range order of KNN,and greatly reduces the average grain size of the whole ceramic system,so that the whole ceramic system has a higher breakdown strength.When x=0.15,the component with the best energy storage performances was obtained.At this time,the 0.85KNN-0.15SBMT ceramic obtained the Wrec of 2.2 J·cm-3 at 252 kV·cm-1,with the corresponding ηbeing 80%.In addition,in the temperature range of 20-100℃,the Wrec and η of the 0.85KNN-0.15SBMT ceramic are very small fluctuation,indicating that it has excellent temperature stability.However,the Wrec fluctuation is very small,but theη fluctuation is very large in the frequency range of 1-100 Hz,so its frequency stability is poor.2.(K0.5Na0.5)1-2xBixNb1-xZrO3(short for KNBNZ-x)lead-free energy storage ceramics were prepared by the traditional solid-state method.The results show that the addition of Bi3+ and Zr4+ breaks the original ferroelectric long-range order of KNN,reduces the average grain size and improves the breakdown strength of the whole ceramic system.When x=0.12,the component with the best energy storage performance was obtained.The KNBNZ-0.12 ceramic can obtain Wrec of 2.78 J·cm-3 under the electric field of 270 kV·cm-1,and the corresponding η is 75.56%.The Wrec and η fluctuated greatly in the temperature range of 20-120℃,indicating it has poor temperature stability.However,the Wrec and η fluctuated very little in the frequency range of 1-100 Hz,indicating it has high frequency stability.3.(K0.5Na0.5)1-xLax/3Nb1-xTaxO3(short for KNLNT-x)lead-free energy storage ceramics were prepared by the traditional solid-state method.The results show that the addition of La3+ and Ta5+ can greatly reduce the average grain size of the whole ceramic system,obtain the ultrahigh breakdown strength,break the ferroelectric long-range order of KNN,and improve the relaxor behavior.Among them,KNLNT-0.09 ceramic with the best performances can obtain a Wrec of 3.51 J·cm-3 at an ultrahigh electric field of 410 kV·cm-1,with a corresponding η of 64.5%.In addition,the fluctuation of Wrec and η of is very small in the temperature range of 20-120℃ and frequency range of 1-100 Hz,which proves that the temperature stability and frequency stability of KNLNT-0.09 ceramic are excellent.4.(K0.5Na0.5)1-3/2xBi3/2xNb1-xMgxO3(short for KNBNM-x)lead-free energy storage ceramics were prepared by the traditional solid-state method.The results show that the addition of Bi3+ and Mg2+breaks the long-range order of ferroelectric and enhances the relaxor behavior.In addition,the average grain size of the whole ceramic system is greatly reduced,which provides an important basis for obtaining an ultrahigh breakdown strength.The KNBNM-0.08 ceramic with the best energy storage performances can obtain a Wrec of 4.5 J·cm-3 under an ultrahigh electric field of 500 kV·cm-1,and the corresponding η is 55.5%.The small fluctuation of Wrec and η in the temperature range of 20-100℃ proves that the temperature stability of the ceramic is excellent.The large fluctuation of Wrec and η in the frequency range of 1-100 Hz indicates that the frequency stability of the ceramic is low.