Enhanced Electrocaloric Effect and Energy Storage Density in Lead‐Free 0.8Na_0.5Bi_0.5TiO₃‐0.2SrTiO₃ Ceramics

Abstract

Enhanced electrocaloric response in lead-free 0.8Na 0.5 Bi 0.5 TiO 3 -0.2SrTiO 3 (NBT-0.2ST) ceramics are investigated using an indirect approach based on Maxwell's relations over a wide operating temperature range. The electrocaloric effect (ECE) is obtained over a broad temperature range with the maximum temperature change (ΔT) value reaching 0.75 K at the working temperature of 400 K under the electric field of 35 kV cm À1 . The maximum EC coefficient (ζ ¼ ΔT=ΔE) is found to be 0.022 KÁcm kV À1 at 400 K. Energy storage density of NBT-0.2ST are calculated and found to be 0.36 J cm À3 at 393 K. High value of ECE and a wide working temperature range (350-450 K) make it a promising lead-free ferroelectric material for applications in cooling technologies.

Electroceramics for High-Energy Density Capacitors: Current Status and Future Perspectives

“…NBT-based ceramics are promising candidates of lead-free dielectrics due to their high P max and T c . However, their large hysteresis and low BDS are not ideal for high energy density capacitor applications. − Attempts to improve their properties generally fall into the following approaches: (i) doping on the A-site (Ba, Sr, K, Li, La, Dy, Nd) ,,,− and B-site (commonly Nb) and codoping (K,Sr/Nb; K,La/Zr; Li,K,Sr/Ta,Nb; K,Mg/Nb; Ba/Nb; Ba/Sn; Ba/Sn,Zr; Ba/Ta; Ba/Zr; Ba,Ca/Zr; Ba,K,Ca/Nb,Zr; Ba/Mg,Nb; Ba/Mg; Ba,La/Al,Nb; Ba,Sr/Yb,Nb; Ba/Hf; La/Al; La,Ba/Nb; Sr/Sn; Sr/Zr; Sr/Mg; Sr/Mg,Nb); ,− (ii) forming solid solution with other end-members, such as AN, NN, and SBT; ,− (iii) using additives such as MnO, Fe 2 O 3 , MgO, SnO 2 , ZnO, CaO, and ZrO 2 ,,,− and (iv) employing different processing methods such as hot-pressing and synthesis using sol–gel derived powders. ,,,, The energy storage properties of NBT-based materials are summarized in Table .…”

Achieved High Energy Density and Excellent Thermal Stability in (1-x)(Bi0.5Na0.5)0.94Ba0.06TiO3-xBi(Mg0.5Ti0.5)O3 Relaxor Ferroelectric Thin Films

“…Moreover, the γ value first increases and then decreases with the increment of BMT content, reaching a maximum value of 1.97 in BNBT-0.5BMT thin films. By reason of the inhomogeneities of size and charge differences around the substituting ions, which gives rise to the distortion of local structure and thereby leading to the generation of the local random electric field [37,38]. The presence of local random electric fields disrupts the long-range dipole order and gives rise to the formation of PNRs, enabling the structural evolution from the ferroelectric phase to the relaxor phase [39].…”