Research On Energy Storage Performance Of （1-x）NaNbO_3-xSr_0.7Bi_0.2TiO₃ Ceramics And The Method Of Energy Storage Efficiency Test

In recent years,with the continuous advancement of the energy transition,the development of energy storage technology has received great attention in related fields.At present,electric energy storage devices are mainly divided into chemical energy storage equipment,electrochemical capacitor and dielectric capacitor.Among them,the dielectric capacitor is widely used in pulse discharge and power devices due to its ability to release the stored energy in a very short time and produce strong pulses or strong currents.As one of the important materials of dielectric capacitors,lead-free antiferroelectric ceramic has large dielectric constant,low dielectric loss,high breakdown field strength,good temperature stability,good fatigue resistance and more clean and environmental protection,which makes it have a wide application prospect in the field of energy storage.Niobate-based lead-free ceramics,as one of the research systems of lead-free energy storage ceramics,have high Curie temperature and electromechanical coupling coefficient,among which the most striking is the energy storage ceramics system with NaNbO₃ as the base.NaNbO₃ can form solid solution ceramics with different characteristics with ferroelectric body or antiferroelectricity of various structures,and has good energy storage performance after doping modification.In the study of energy storage performance,the energy storage efficiency of the material is also one of its important indicators.At present,the hysteresis loop measurement is usually used to calculate the energy storage efficiency.However,this method still has many disadvantages.For example,the hysteresis loop of the ferroelectric material only the polarization caused by the electric domain reversal process can accurately reflect the ferroelectric performance of the material,and the hysteresis loop will be disturbed by induced polarization,conductance and other factors,and therefore cannot accurately react the ferroelectric properties of the material.In addition,the high voltage output by the high-voltage source has a certain probability of breakdown of the sample and causing the sample cannot be tested twice.Based on the above ideas,a series of（1-x）NaNbO₃-x Sr_0.7Bi_0.2Ti O₃ ceramic samples were prepared by conventional solid phase reaction method,and their crystal structure and micromorphology were studied,and then the energy storage performance of different doping components and different sintering temperatures were analyzed.In its energy storage efficiency test method,this paper prepared a vertical contact separation triboelectric nanogenerator,and built a set of ceramic energy storage efficiency test circuit,and tested the energy storage efficiency value of the corresponding ceramic samples.In addition,this paper uses the prepared ceramic capacitors with different resistors to achieve high-pass and low-pass filtering of the output signal of the triboelectric nanogenerator.This paper draws the following conclusions:1.The 0.7NaNbO₃-0.3Sr_0.7Bi_0.2Ti O₃（0.7NN-0.3SBT）ceramic sample is a single perovskite structure,compared with pure NaNbO₃,the grain size of the 0.7NN-0.3SBT ceramic sample is reduced and the microscopic structure are more compact.With the increase of Sr_0.7Bi_0.2Ti O₃ doping,the hysteresis loop of the corresponding sample becomes more elongated,and the dielectric loss is reduced,and the energy storage efficiency of the sample increases accordingly,the saturation polarization intensity decreases with the amount of SBT doping at the same time.The results show that the 0.7NN-0.3SBT sample achieves the relatively optimal energy storage performance at the sintering temperature of 1180℃,the breakdown field strength reaches 179.9k V/cm,the maximum polarization strength is 43.8μC/cm²,and the energy storage density is 1.54J/cm³,the energy storage efficiency is 34%.2.The vertical contact separation triboelectric nanogenerator prepared by PTFE film and aluminum foil material with large electronic affinity energy as electrodes reaches the maximum output power of the device of 4m W when the load resistance is 10MΩand the vibrator frequency is2Hz,10MΩis the matching impedance value of the device.3.The ceramic energy storage efficiency test loop based on the triboelectric nanogenerator has low charging loss and the highest charging efficiency reaches 93.77%.At the same time,the test results show that the parameter values obtained by the test method of ceramic energy storage efficiency proposed in this experiment are consistent with the results obtained by the ferroelectric tester on samples with different thicknesses and the values are close,which shows that the energy storage efficiency obtained by charging and discharging the ceramic capacitor through the triboelectric nanogenerator is accurate and reliable.4.The triboelectric nanogenerator band-pass filter circuit based on ceramic capacitors has good filtering effect,and due to the lead-free characteristics of ceramic capacitors,it will not pollute the environment and can be reused.The results show that when the output signal is turned on at both ends of the low-pass filter,and when the pressing frequency of the triboelectric nanogenerator drops from17.3Hz to 10.3Hz,the voltage value of the output sine wave rises from 88.8V to 100.9V.When the output signal is turned on to both high-pass filter ends,and when the pressing frequency of the triboelectric nanogenerator drops from 17.3Hz to 13.3Hz,the voltage value of the sine wave drops from 126.0V to 105.8V.