Investigations On The Preparation And Energy Storage Properties Of Lead-free Antiferroelectric Sliver Niobite Based Ceramics

In recent years,the Ag Nb O₃ antiferroelectric?AFE?ceramics have attracted much attention for their good energy storage properties and environmentally friendly characteristics.However,right now Ag Nb O3 cannot be commercialized due to the lower energy density.Thus it's critical to improve the energy storage performance of silver niobate ceramics.In this thesis,the energy storage properties of silver niobate-based ceramics were investigated in terms of the A-site doping and the thick film ceramic process.The research contents and obtained results for sliver niobite-based ceramics were summarized as follows.:Firstly,ceramics of composition Ag_1-2xCa_xNb O₃?0.00?x?0.04?were prepared using a traditional solid-state reaction method.Their structure and energy storage properties were characterized.Dense Ag_1-2xCa_xNb O₃ ceramics were prepared successfully using a two-step sintering approach.The results show that?E(E_AFE-FE?up?-E_FE-AFE?down?)gradually decreases with the Ca²⁺dopant,thus causing the hysteresis loop to become"slimmer"and the energy storage efficiency be enhanced.An energy density W_rec of 1.30 J/cm³ and the efficiency of 86.7%were procured in Ag_0.96Ca_0.02Nb O₃ bulk ceramic,which has a better energy storage density and energy storage efficiency compared to other component samples.Secondly,silver niobate?AN?ceramic powder was prepared using a solid-state reaction method,and silver niobate thick film ceramics were prepared by tape-casting process.The results indicate that the rheological properties of the casting slurry was best,when the solid phase was 45 wt%,the dispersant 0.4 wt%,the binder 4.0 wt%,and the proportion of plasticizer and binder was 0.5.The dense silver niobate thick-film ceramics were procured using two-step sintering approach,and their energy storage density and energy storage efficiency were 2.37 J/cm³ and 45%,respectively.As the temperature increases,its energy storage density and energy storage efficiency increase to 2.98 J/cm³and 53%with the increase of temperature.Therefore,the energy storage performances of silver niobate ceramics can be further improved using the tape-casting method.Finally,ceramics of composition Ag_1-2xSr_xNb O₃?0.005?x?0.030?were prepared using a traditional solid-state reaction method.Their structure and energy storage properties were characterized.It's well known that the stability of an antiferroelectric phase of Ag_1-2xSr_xNb O₃ thick film ceramics can be evaluated by the tolerance factor?t?and electronegativity difference.Then the Sr²⁺ions were doped in order to increase the random distribution of A-site cations and break the long-range ordering of the lattice structure,leading to disordered local structures and relaxor ferroelectric behaviors,and further to reduce the?E to decrease and increasing energy storage density and energy effciency.The results indicate that the energy storage performances of SANx thick film ceramics can be enhanced after the Sr²⁺ionic doping.The energy storage density of SAN3sample was 3.11 J/cm³,and the energy storage efficiency was 50%.