Remarkably enhanced dielectric stability and energy storage properties in BNT—BST relaxor ceramics by A-site defect engineering for pulsed power applications

Abstract

Lead-free bulk ceramics for advanced pulsed power capacitors show relatively low recoverable energy storage density (Wrec) especially at low electric field condition. To address this challenge, we propose an A-site defect engineering to optimize the electric polarization behavior by disrupting the orderly arrangement of A-site ions, in which $${\rm{B}}{{\rm{a}}_{0.105}}{\rm{N}}{{\rm{a}}_{0.325}}{\rm{S}}{{\rm{r}}_{0.245 - 1.5x}}{_{0.5x}}{\rm{B}}{{\rm{i}}_{0.325 + x}}{\rm{Ti}}{{\rm{O}}_3}$$ Ba 0.105 Na 0.325 Sr 0.245 − 1.5 x □ 0.5 x Bi 0.325 + x TiO 3 ($${\rm{BN}}{{\rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{\rm{B}}_{0.325 + x}}{\rm{T}}$$ BNS 0.245 − 1.5 x □ 0.5 x B 0.325 + x T , x = 0, 0.02, 0.04, 0.06, and 0.08) lead-free ceramics are selected as the representative. The $${\rm{BN}}{{\rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{\rm{B}}_{0.325 + x}}{\rm{T}}$$ BNS 0.245 − 1.5 x □ 0.5 x B 0.325 + x T ceramics are prepared by using pressureless solid-state sintering and achieve large Wrec (1.8 J/cm3) at a low electric field (@110 kV/cm) when x = 0.06. The value of 1.8 J/cm3 is super high as compared to all other Wrec in lead-free bulk ceramics under a relatively low electric field (< 160 kV/cm). Furthermore, a high dielectric constant of 2930 within 15% fluctuation in a wide temperature range of 40–350 °C is also obtained in $${\rm{BN}}{{\rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{\rm{B}}_{0.325 + x}}{\rm{T}}$$ BNS 0.245 − 1.5 x □ 0.5 x B 0.325 + x T (x = 0.06) ceramics. The excellent performances can be attributed to the A-site defect engineering, which can reduce remnant polarization (Pr) and improve the thermal evolution of polar nanoregions (PNRs). This work confirms that the $${\rm{BN}}{{\rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{\rm{B}}_{0.325 + x}}{\rm{T}}$$ BNS 0.245 − 1.5 x □ 0.5 x B 0.325 + x T (x = 0.06) ceramics are desirable for advanced pulsed power capacitors, and will push the development of a series of Bi0.5Na0.5TiO3 (BNT)-based ceramics with high Wrec and high-temperature stability.

Significantly Enhanced Energy Storage Performance in High Hardness BKT-Based Ceramic via Defect Engineering and Relaxor Tuning

“…However, the attractive energy storage potential of BKTBFO ceramic is accompanied by some serious problems. Concerning the valence floating of Fe 3+ and the volatilization of Bi 2 O 3 during sintering (as demonstrated by defect eqs and ), the high oxygen vacancy content promotes the enhancement of leakage current, which deteriorates the BDS performance of BKTBFO ceramics . Here, we suggest a method of donor doping to enhance BDS by compensating for oxygen deficiency, as represented by the defect equations below 3 normalF normale 3 + + normalO 2 − → 2 normalF normale 2 + + V normalO • • + 1 2 normalO 2 2 normalB normali normalB normali × + 3 normalO normalo × → normalB normali 2 normalO 3 false↑ prefix+ 3 V normalO • • + 2 V normalB normali ‴ normalN normalb 2 normalO 5 true → normalF normale 2 normalO 3 2 normalN normalb normalF normale • ...…”

“…Concerning the valence floating of Fe 3+ and the volatilization of Bi 2 O 3 during sintering (as demonstrated by defect eqs 1 and 2), the high oxygen vacancy content promotes the enhancement of leakage current, which deteriorates the BDS performance of BKTBFO ceramics. 23 Here, we suggest a method of donor doping to enhance BDS by compensating for oxygen deficiency, as represented by the defect equations below…”

Boosting dielectric temperature stability in BNBST‐based energy storage ceramics by Nb2O5 modification

“…The smaller the absolute value of TCC is, the better its temperature stability is. Basically, the TCC can be calculated by Equation (1), 28 where ε T and ε 25 • C are the dielectric constant tested at temperature T and the reference dielectric constant at 25 • C, respectively. Figure 4B shows the calculated TCC from Equation (1) for BNB-STC + x wt%Nb 2 O 5 ceramics in the temperature range of −55 to 200 • C with ±0.15 as the reference standard.…”

“…[21][22][23][24][25][26] However, the large remnant polarization (P r ∼ 38 μC/cm 2 ) and high coercive field (E c ∼ 70 kV/cm) make the P-E hysteresis loop of BNT ceramic showing a fat shape, which needs to be slim and then suitable for energy storage applications. 27,28 Meanwhile, the ε r of BNT ceramics in the low-temperature region is very low, which leads to poor dielectric temperature stability, and greatly restricts its application in the wide temperature region. [29][30][31] In our previous work, we used Ba 0.3 Sr 0.7 TiO 3 (BST) and Bi 0.5 Na 0.5 TiO 3 (BNT) as end-members to construct a solid solution, and an optimized composition (Bi 0.5 Na 0.5 ) 0.65 (Ba 0.3 Sr 0.7 ) 0.35 TiO 3 (BNBST) was obtained potential for energy storage applications.…”

“…Of which sodium bismuth titanate (Bi 0.5 Na 0.5 TiO 3 , BNT) is a typical lead‐free ferroelectric ceramic with high Curie temperature ( T c ∼ 320°C), large saturated polarization ( P s > 40 μC/cm 2 ) and diffusive phase transition behavior for temperature‐dependent dielectric constant ( ε r – T ) curve, and regarded as one of the most promising and competitive environment‐friendly ferroelectric ceramics 21–26 . However, the large remnant polarization ( P r ∼ 38 μC/cm 2 ) and high coercive field ( E c ∼ 70 kV/cm) make the P – E hysteresis loop of BNT ceramic showing a fat shape, which needs to be slim and then suitable for energy storage applications 27,28 . Meanwhile, the ε r of BNT ceramics in the low‐temperature region is very low, which leads to poor dielectric temperature stability, and greatly restricts its application in the wide temperature region 29–31 …”