Dielectric Storage Properties Of BCTS Ceramics At Low Voltage

Although dielectric energy storage devices have been widely used at high voltage level,with the rapid development of portable and wearable electronic devices,the demand for energy storage devices under finite electric field strength is also growing.In this paper,several methods for improving the energy density of?Ba,Ca??Ti,Sn?O₃ ferroelectric material system under low electric field are proposed,and the dielectric relaxation properties are systematically studied.The research results have certain guiding significance for the development of energy storage medium with large dielectric constant and high energy density under low electric field.Firstly,the effects of sintering atmosphere on the microstructure,dielectric relaxation properties,piezoelectric properties and storage properties of BCTS ceramics were investigated.The experimental results show that a certain degree of oxygen partial pressure will affect the BCTS grain morphology and change the proportion of phase coexistence.In addition,nitrogen sintering enhances the relaxation of the sample and improves the temperature stability of the dielectric constant.On the other hand,the P-E curves of samples sintered in nitrogen become“thinner”,which improves the energy storage density and efficiency.Then the effects of doping elements on the microstructure,dielectric relaxation,piezoelectric and storage properties of BCTS ceramics were studied,including MnO₂,BiScO₃,HfO₂ and ZrO₂.Through the substitution of specific lattice position elements and grain boundary enrichment,the crystal symmetry,micro-domain structure and defect structure of the material system are adjusted to optimize the electrical properties of the material.?1?The addition of MnO₂ changed the coexistence ratio of O phase and T phase,and the O-T phase boundary of the ceramic was obtained.A good combination of piezoelectric property could be achieved with the addition of 0.4 mol.%MnO₂.The mechanical quality factor Q_m,dielectric loss tan?,piezoelectric constant d₃₃,and planar electromechanical coefficient k_p measured are 216,0.011,578 pC/N,and 0.39,respectively.Due to the influence of the internal bias field,when the addition amount of MnO₂ is 0.8 mol.%,the optimal storage performance is obtained(W_rec¹7.86 mJ/cm³,?⁴7.87%).?2?The addition of BiScO₃ causes the ceramic grain size to decrease significantly,and the C-T peak and T-O peak gradually disappear,accompanied by an increase in peak value and an increase in range.Moreover,it is found that the relaxation ferroelectric behavior of BCTS-6BSO ceramics is a thermal activation process.In addition,BiScO₃ also improves the energy storage performance of the sample.As the content of BiScO₃ increases,the P-E curve becomes finer,the maximum polarization decreases,and the closed area becomes smaller.The BCTS-2BSO ceramic sample achieves optimal storage performance(W_rec¹8.6541mJ/cm³,?⁶2.066%).?3?The addition of HfO₂ increases the temperature stability of the dielectric constant of the ceramic,and the dispersion of the first transition peak is enhanced and the peak value is increased.When HfO₂ content is 8 mol.%,Curie temperature suddenly drops to 4?,breaking the coexistence of O phase and T phase,turning into only O phase.The addition of HfO₂ also improved the energy storage performance of ceramics,and the BCTS-4Hf ceramic samples obtained the best storage performance(W_rec¹6.7232mJ/cm³,?⁴7,24%).?4?The addition of Zr improves the dielectric properties.As the Zr content increases,the dispersion of phase transition increases and the phase transition temperature?T_C?decreases.At the same time,the change of Zr content also affects its storage performance,and the best storage performance is obtained at x=0.03(W_rec¹9.84 mJ/cm³,?⁶1%).By fitting the relationship between the microstructures and the properties of the samples,it is preliminarily concluded that in BCSTZ system,the smaller the grain size,the denser the structure and the higher the dielectric storage performance.