Preparation And Research Of Energy Storage Properties Of SrTiO₃-Na_0.5Bi_0.5TiO₃ Ceramics

The trend toward miniaturization,power integration,and compounding of high-power pulse devices has led to the development of capacitors with high permittivity,low dielectric loss,and high withstand voltage,which have become hot topics in the industry.SrTiO₃?ST?is a linear material of perovskite?ABO₃?with a Curie temperature much lower than room temperature?-250°C?,,low dielectric loss and high breakdown strength provides a foundation for obtaining higher energy density.In order to let the Curie temperature close to the room temperature,doping with A and B sites to ensure the higher efficiency.Therefore,Na_0.5Bi_0.5TiO₃?NBT?,BaTiO₃?BT?,KNbO₃?KN?and SnO₂,MgO are introduced into the ST powder.The Curie temperature is adjusted to convert the ST-based ceramic into a relaxor,enhancing its relaxor characteristics,polarization performance and breakdown strength,its lower energy loss.And its crystal structure,microscopic morphology,dielectric,relaxation,ferroelectricity and energy storage properties are characterized.?1-x?ST-xNBT ceramics were synthesized by solid-phase reaction method.XRD and Raman showed that with the increase of NBT content,the samples exhibit a pseudo-cubic perovskite,and the unit-cell parameters increased.All samples show obvious dielectric broad peaks and more pronounced frequency dispersion.The ceramic has relaxor over a wide temperature range,which is mainly due to the increase in lattice disorder and the thermal evolution of PNRs.As the content of NBT increases from 0.1 to 0.6,the temperature?T_m?corresponding to the peak increases from-118°C to 106°C@1 kHz.When x=0.1-0.4,the increase of the polarization phase of ceramic with x does not cause a significant increase in the energy loss during charge-discharge.Among them,when x=0.2-0.4,the sample reached higher discharge energy density(1.58-1.70J·cm^-3)under its critical electric field.?0.8-x?ST-0.2NBT-xBT relaxor were synthesized by the solid-phase method.The introduction of BT does not change the original pseudo-cubic perovskite structure of ceramics.A broad peak region is observed.The introduction of BT caused the T_m increase continuously.The slim hysteresis loop disappeared with the increase of BT content,and the saturation polarization of sample increased significantly,indicating that the introduction of BT induced the gradual enhancement of the ferroelectric phase.The x=0.35 sample has a breakdown strength of up to 17 kV·mm^-1,a maximum polarization of up to 29.19?C·cm^-2,a maximum discharge energy density of 1.78 J·cm^-3,and an energy storage efficiency of 77.06%.?1-x??0.45ST-0.2NBT-0.35BT?-xSn O₂ ceramics were prepared by the solid phase method.With the increase of SnO₂ concentration,the average grain size of the ceramic decreases from 2.5?m to 0.8?m,which is very beneficial for the improvement of the breakdown strength.When x=0.07,the breakdown strength of the sample is as high as 24 kV·mm^-1.All ceramics have a slim hysteresis loop.The introduction of SnO₂ can effectively improve its energy storage applications.The discharge energy density of the x=0.07 sample under a 24 kV·mm^-1 electric field is as high as 2.25 J·cm^-3,and the energy storage efficiency is 79.51%.?1-x?Sr_0.5Na_0.25Bi_0.25TiO₃-5 wt%MgO-xKN ceramics were prepared by the solid phase method.When x=0.05,the grain size reaches a minimum?1.40?m?.The two dielectric peaks represent the presence of low-temperature polar nanometer-size regions?LT-PNRs?and high-temperature polar nanometer-size regions?HT-PNRs?,respectively.The addition of KN changed the volume ratio between LT-PNRs and HT-PNRs.When x=0.05,the sample meets the X9R standard.The hysteresis loops of ceramics exhibits the slim shape.The doping of KN can significantly reduce the remnant polarization of the sample.When x=0.05,the polarization difference of the sample is as high as 26.24?C·cm^-2,the breakdown strength is as high as 17.85 kV·mm^-1,and energy storage efficiency is 76.34%,which makes it have excellent energy storage density 2 J·cm^-3.