Preparation And Properties Of Bi_0.5Na_0.5TiO₃-Based Energy Storage Ceramic Materials

Energy storage dielectric ceramic,an important component of capacitors and other dielectric devices,is a basic functional material widely used in communication,automotive electronic circuit equipment,military industry and other fields.At present,most of the commercial dielectric ceramics are lead-based antiferroelectric ceramics containing lead elements harmful to human and environment.However,most of the environment-friendly lead-free dielectric ceramics possess inferior energy storage characteristics.With the excessive consumption of non-renewable resources and the increasingly serious environmental pollution,it has become an extremely important and urgent research topic to develop lead-free energy storage dielectric ceramic materials with high performances and no harm to environment and human.This thesis is devoted to improving the energy storage characteristics of lead-free dielectric ceramics and comprehensively analyzing their related properties.The(1-x)(Na0.5Bi0.5)0.7Sr0.3TiO1-xSr(Ti0.85Zr0.15)O3(denoted as(1-x)NBST-xSTZ)energy storage ceramics were fabricated by traditional solid-state sintering method.The results reveal that the suppressed remanent polarization and enhanced breakdown strength of NBST ceramics can be obtained by introducing the linear additive of STZ.A giant recoverable energy density(Wrec=3.13 J·cm-3)accompanied by an ultrahigh energy efficiency(?=91.14%)were synchronously observed in 0.70NBST-0.30STZ ceramic under 262 kV·cm-1.The potential origin of the improved breakdown strength is revealed by analyzing the band structure and the density of states.Moreover,the excellent temperature stability(20?-140?)and frequency stability(1 Hz-200 Hz)has also been achieved at 200 kV·cm-1.More importantly,the ultrahigh power density(PD)of 41.24 MW·cm-3,the transitory discharge time(t0.9=125.6 ns)and outstanding thermal stability(20?-120?)can also be achieved for 0.70NBST-0.30STZ ceramic.The(1-x)(Na0.5Bi0.5)0.7Sr0.3TiO3-xBi(Mg2/3Nb1/3)O3[denoted as(1-x)NBST-xBMN]energy storage ceramics were fabricated via traditional solid-state sintering method.We utilized a strategy to achieve synergistic enhancement of energy density and energy efficiency in the(1-x)NBST-xBMN systems based on refined grain size and the introduction of Bi3+,s lone pair electron 6s2 configuration,respectively.As a result,a giant recoverable energy density of 3.45 J·cm-3 and a high energy efficiency of 88.01%were simultaneously achieved in the 0.85NBST-0.15BMN ceramic,which precede those of recently reported lead-free dielectric ceramic materials.Meanwhile,excellent temperature(30?-150?)and frequency(1 Hz-100 Hz)stability were also observed at 200 kV·cm-1.Moreover,an outstanding power density(PD)of 38.47 MW·Cm-3 and an ultrafast discharge rate(t0.9)of 52.8 ns were also achieved in the 0.85NBST-0.15BMN ceramic at 120 kV·cm-1.The(1-x)(Na0.5Bi0.5)0.7Sr0.3TiO3-xBi(Ni0.5Sn0.5)O3(denoted as(1-x)NBST-xBNS)energy storage ceramics were fabricated by traditional solid-state sintering method.The results reveal that the 0.90NBST-0.10BNS ceramic with significantly improved recoverable energy density(4.18 J·cm-3)and satisfactory energy efficiency(83.64%)compared to other lead-free dielectric ceramics through the incorporation of BNS,due to the increased breakdown strength and suppressed the remnant polarization.The first-order reversal curve(FORC)measurements indicate that the addition of BNS could break the order of long-range ferroelectricity and improved the relaxation.The 0.90NBST-0.10BNS ceramic also possesses an outstanding temperature and frequency stability of energy storage properties in the range of 20?-140? and 1 Hz-100 Hz,respectively.More importantly,discharge properties characterized by a preeminent power density(36.19 MW·cm-3),transient energy release times(144.2 ns),and high discharge energy density(1.16 J·cm-3)also synchronously observed in 0.90NBST-0.10BNS ceramic.The(1-x)(Na0.5Bi0.5)0.7Sr0.3TiO3-xBi(Mg0.5Zr0.5)O3(denoted as(1-x)NBST-xBMZ)energy storage ceramics were fabricated using traditional solid-state sintering method.The results reveal that a ultrahigh recoverable energy density(4.48 J·cm-3)and a satisfactory energy efficiency(83.3%)compared to other lead-free dielectric ceramics was obtained in the optimal composition 0.85NBST-0.15BMZ ceramic,thanks to the incorporation of BMZ that increased breakdown strength and suppressed the remnant polarization.Furthermore,both energy density and energy efficiency of the 0.85NBST-0.15BMZ ceramic also possessed outstanding temperature and frequency stability in the range of 30?-150? and 1 Hz-100 Hz,respectively.More importantly,discharge properties characterized by an excellent power density(33.9 MW·cm-3),transient energy release times(87.4 ns),and high discharge energy density(0.63 J.cm-3)also synchronously observed in 0.85NBST-0.15BMZ ceramic.