Study On Doping Modification Of Strong Field Electrical Properties In BNT-BT-Based Ferroelectric Ceramics

Ferroelectric ceramics is a very important functional material,which has been applied in every corner of human life and production,such as national defense,aerospace,electronic communication,medicine,industrial and daily household appliances.In this paper,lead-free relaxation ferroelectric ceramics?1-x?(Bi_0.44Na_0.44Ba_0.12TiO₃)-x?LiNbO₃?and?1-x?(Bi_0.445Na_0.445Ba_0.11TiO₃)-x(?BaTiO₃?_0.5-(BiMg_0.5Ti_0.5O₃)_0.5)are fabricated by the conventional solid-state reaction method,and LiNbO₃and BT-BMT doping BNT-BT-based ceramics located near the morphotropic phase boundary.The effects of doping content on microstructure,dielectric property,strong field electrical properties?electrostrain performance,electrocaloric effect and energy storage?of the two systems were systematically studied.The results show that:With the increase of LiNbO₃ doping amount,the grain size of ceramic decreases and the density of the ceramics increases.the phase structure will change from ferroelectric tetragonal phase?P4mm?to relaxation antiferroelectric tetragonal phase?P4bm?.Moreover,the dielectric relaxation dispersion of the ceramic will increase.Moderate LiNbO₃doping can improve the electrical properties in the strong electric fields of the material.A large electrostrain?maximum⁰.34%at 100 kV/cm and room temperature?with high thermal stability over a temperature range?303 K-383 K?is obtained at x=0.03,which is originated from the increase of relaxation antiferroelectric tetragonal phase?P4bm?.A large energy storage density is attributed to the transition from a typical ferroelectric to a relaxor ferroelectric?maximum W⁰.67 J/cm³ at 100kV/cm and room temperature?with a high efficiency??⁴9.3%?is achieved at x=0.06.Moreover,a phase-induced large negative electrocaloric?EC?effect?maximum?T¹.71 K and?S^-2.25 J/?K·kg?at 70 kV/cm?is also obtained at x=0.04.The phase structure of the pure BNT-11BT and the pure BT-BMT component ceramics are dominated by ferroelectric phase and relaxation antiferroelectric phase respectively.The phase structure of?1-x??BNT-11BT?-x?BT-BMT?)ceramics transforms from ferroelectric tetragonal phase?P4mm?to relaxation antiferroelectric tetragonal phase?P4bm?by BT-BMT doping.Moderate BT-BMT doping can improve the electrical properties in the strong electric fields of the material.A large electrostrain?maximum⁰.37%at 100 kV/cm and room temperature?is obtained at x=0.16.Compared with LiNbO₃ doped ceramic,its electrostrain is increased slightly.A large energy storage density?w⁰.78 J/cm³?and a high efficiency??⁵0.51%?are achieved at x=0.24 induced by 100kV/cm eletric fiield at room temperature.Moreover,a phase-induced large negative electrocaloric?EC?effect?maximum?T².17 K and?S^-3.87J/?K·kg?at 60 kV/cm?is also obtained at x=0.16.