Energy Storage Performance And Electrocaloric Effect In Mechanical Strain Modified BNT-11BT Based Ceramics

Ferroelectric/antiferroelectric materials with high performance and their electronic components have broad application prospects in the fields of national defense,aerospace,electronic communication,and household appliances,etc.In this article,the BNT-BT based ferroelectric ceramics located near the morphotropic phase boundary(MPB)were prepared by solid state reaction method.Micro-sized,submicro-sized and nano-sized powders were prepared by applying various mechanical stress to the calcined powder,and then different-sized powders were sintered to ceramics.The dielectric properties,ferroelectric properties,energy storage and electrocaloric effect of BNT-11BT-xBFO(x = 0,0.03,0.06,0.09)ceramics with Bi deficiency were systematically investigated.Some interesting results were obtained:1.With the increase of rhombohedral BFO,the tetragonal ferroelectric phase(P4mm)in the BNT-BT ceramic near the morphotropic phase boundary(MPB)would gradually transform into the tetragonal antiferroelectric phase(P4bm),indicating that the addition of BFO is beneficial to the movement of the MPB to the ferroelectric phase region.Moreover,the tetragonal ferroelectric phase of the material would gradually transform into tetragonal antiferroelectric phase with the increasing of the mechanical stress.2.With the increase of mechanical stress in the ceramic powder,the energy storage properties(density and efficiency)of the corresponding ceramics would be improved gradually.The improvement of the energy storage properties for the pure BNT-BT ceramic is the most remarkable.The energy storage density(W)and efficiency(rj)of ceramics prepared by nano-sized powder at room temperature are 0.766 J/cm3 and 72.2%,respectively,which show enhancement of 343%and 363%over that of the ceramics prepared by micro-sized powder(W一 0.173 J/cm3,η～15.58%),respectively.In addition,the ceramics prepared by nano-sized powder also exhibit good thermal stability.The energy efficiencies are all larger than 80%in a broad temperature range of 120 K(333 K～453 K),and the best energy storage properties are obtained at 353 K(～0.847 J/cm3,η～84.39%).3.The ceramic(x = 0.06)prepared by submicro-sized powder obtained a large electrocaloric effect with a maximum ΔTvalue of-1.1 K under the electric field of 29.775 kV/cm.The large electrocaloric effect is mainly ascribed to the coupled effects of large mechanical stress in the ceramic powder,higher content of BFO doping and high Bi deficiency,etc.