Mechanical confinement for improved energy storage density in BNT-BT-KNN lead-free ceramic capacitors

Abstract

Enhanced energy storage density by inducing defect dipoles in lead free relaxor ferroelectric BaTiO 3 -based ceramics Applied Physics Letters 110, 132902 (2017); 10.1063/1.4979467On the phase identity and its thermal evolution of lead free (Bi 1/2 Na 1/2 )TiO 3 -6 mol% BaTiO 3 Journal of Applied Physics 110, 074106 (2011); 10.1063/1.3645054Influence of structural evolution on energy storage properties in Bi 0.5 Na 0. With the advent of modern power electronics, embedded circuits and nonconventional energy harvesting, the need for high performance capacitors is bound to become indispensible. The current state-of-art employs ferroelectric ceramics and linear dielectrics for solid state capacitance. However, lead-free ferroelectric ceramics propose to offer significant improvement in the field of electrical energy storage owing to their high discharge efficiency and energy storage density. In this regards, the authors have investigated the effects of compressive stress as a means of improving the energy storage density of lead-free ferroelectric ceramics. The energy storage density of 0.91(Bi 0.5 Na 0.5 )TiO 3 -0.07BaTiO 3 -0.02(K 0.5 Na 0.5 )NbO 3 ferroelectric bulk ceramic was analyzed as a function of varying levels of compressive stress and operational temperature .It was observed that a peak energy density of 387 mJ.cm -3

Anti-Ferroelectric Ceramics for High Energy Density Capacitors

“…The expression in Equation (2) can be used to determine the energy density of most ferroelectric materials at their saturation electric field values. Furthermore, since ferroelectric materials are prone to hysteresis losses, another important factor known as material efficiency needs to be determined according to the following relation [37]: $\mathrm{sans-serif\eta }=\frac{U}{U+U_1}$ …”

“…However, upon being subjected to higher magnitude of electric field, the domains themselves are rotated in the direction of the applied electric field. This phenomenon is known as ferroelectric domain switching and is generally associated with 180° domain rotation [37,43,46,58,62,78]. Conversely, when a poled or activated, ferroelectric material is subjected to compressive stress, the domains realign to face away from the direction of stress applied; termed ferroelastic domain switching [43,86,87].…”

“…Figure 1 provides a graphical representation of each of the material classes and their energy storage characteristics as indicated on a polarization versus electric field ( P - E ) hysteresis loop [37]. The hatched area represents dischargeable energy while the area within the hysteresis loop represents dielectric losses.…”

“…Since the transformation is reversible, the ferroelectric phase reverts back to its original anti-ferroelectric form when the applied electric field is reduced below a certain critical value [43,46]. The low hysteresis losses coupled with the reversible phase transformation have been associated with high power and energy density in anti-ferroelectric materials [37,47,48]. Furthermore, the loss of ferroelectric characteristics at low electric field is also responsible for a fast discharge rate and high discharge efficiency in these materials.…”

Enhanced Electrocaloric Effect in Pre‐stressed Ferroelectric Materials

“…This phenomenon has been extensively reviewed in the literature for a number of materials and has been employed for tuning of the ferroelectric response, [40,41] energy harvesting, [36] and energy-storage applications. [33] Coupling the change in free energy of the system due to stress with the change in energy due to polarization can be used to enhance and even control the extent of the ECE in ferroelectric materials. To demonstrate the applicability of our hypothesis, we illustrate the effect for two individual case studies, namely BNT-BT bulk ceramics and PMN-32PT single crystals.…”