Achieving Excellent Energy Storage Properties in Fine‐Grain High‐Entropy Relaxor Ferroelectric Ceramics

Abstract

ABO3‐type high‐entropy relaxor ferroelectric ceramics have rarely been studied in energy storage capacitor owing to easy formation of impurity phase. In this work, single phase (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)TiO3‐xmol%PbO high‐entropy ceramics are fabricated and investigated. The optimal composition of x = 2.0 shows a remarkable comprehensive energy storage performance with high recoverable energy density Wrec = 8.2 J cm–3, ultrahigh efficiency η = 92.2%, excellent temperature stability (Wrec = 4.4 J cm‐3 ± 4%, η = 91% ± 3% within the range of 25–120 °C), and ultrafast discharge rate t0.9 = 5.9 µs. Three key factors, low remnant polarization Pr originating from high‐entropy enhanced relaxation degree, high maximum polarization Pm due to special electronic structure of Pb ion, and high electrical breakdown strength Eb stemming from small grain size, are responsible for the improved energy storage properties. These results provide a novel strategy of developing high‐entropy ceramics to optimize electrical performances including energy storage property.

Electrostatic energy storage performances of La(Ni2/3Ta1/3)O3‐modified Na0.5Bi0.5TiO3 lead‐free ceramics

“…The decreased tan δ favors to reduce the energy loss as heat during charge–discharge process and thus improve E b 1 . To further confirm the improved dielectric relaxation properties, the modified Curie–Weiss law is widely employed based on the equation (Figure 3G) 13,16 : $$$$\begin{equation}\frac{1}{{{\varepsilon _{\rm{r}}}}} - \;\frac{1}{{{\varepsilon _{{\rm{r}},{\rm{max}}}}}} = \frac{{{{\left( {T - {T_{\rm{m}}}} \right)}^\gamma }}}{C}\;\end{equation}$$$$where γ and C are diffusion factor and constant, respectively. The γ value increases monotonically with increasing x , revealing the improved dielectric relaxation behavior quantitatively.…”

“…The decreased tanδ favors to reduce the energy loss as heat during charge-discharge process and thus improve E b . 1 To further confirm the improved dielectric relaxation properties, the modified Curie-Weiss law is widely employed based on the equation (Figure 3G) 13,16 :…”

“…Among various RFE materials, Na 0.5 Bi 0.5 TiO 3 (NBT)‐based ferroelectric ceramics are extensively investigated due to the environment‐friendly compositions, simple preparation process, and excellent electrical properties. Particularly, because of the similar outermost electronic configuration between Bi 3+ and Pb 2+ , the NBT‐based ceramics show relatively large P max 1,3,15–17 . However, the pure NBT and some of their solid solutions, such as NBT–BaTiO 3 , NBT–Bi 0.5 K 0.5 TiO 3 , generally show the nonergodic relaxor (NR) state at room temperature, where the dynamic of PNRs is weak, leading to the irreversible transition between PNRs and long‐range ferroelectric orders.…”

“…Particularly, because of the similar outermost electronic configuration between Bi 3+ and Pb 2+ , the NBT-based ceramics show relatively large P max . 1,3,[15][16][17] However, the pure NBT and some of their solid solutions, such as NBT-BaTiO 3 , NBT-Bi 0.5 K 0.5 TiO 3 , generally show the nonergodic relaxor (NR) state at room temperature, where the dynamic of PNRs is weak, leading to the irreversible transition between PNRs and long-range ferroelectric orders. Accordingly, a ferroelectric-like square P-E loop with a large P r is observed, which is unsuitable for electrostatic energy storage.…”

Screening sintering aids for 0.88(Bi0.4Na0.2K0.2Ba0.2)TiO3–0.12Sr(Mg1/3Nb2/3)O3 high‐entropy dielectric ceramics

“…Recent studies have shown that high-entropy ceramics can be much better energy storage materials than traditional dielectric ceramics. [9][10][11] Recently, the energy storage performance of a high-entropy ceramic, 0.88(Bi 0.4 K 0.2 Na 0.2 Ba 0.2 )TiO 3 -0.12Sr(Mg 1/3 Nb 2/3 )O 3 Tianyu Liu and Bo Yan contributed equally to this work.…”