Lead free 0.94(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)ceramics were prepared by conventional solid-state mixed oxide route with the A-site stoichiometry modified to incorporate donor-doping(through Bi-excess)and accept...Lead free 0.94(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)ceramics were prepared by conventional solid-state mixed oxide route with the A-site stoichiometry modified to incorporate donor-doping(through Bi-excess)and acceptor-doping(through Na-excess).Both stoichiometric and nonstoichiometric ceramics exhibited a single perovskite phase with pseudo-cubic symmetry.A significant improvement in the dielectric properties was observed in Bi-excess compositions and a deterioration in the dielectric properties was observed in Na-excess compositions.Impedance spectroscopy was utilized to analyze the effects of A-site nonstoichiometry on conduction mechanisms.Compositions with Bi-excess resulted in an electrically homogeneous microstructure with an increase in resistivity by3-4 orders of magnitude and an associated activation energy of 1.57 eV which was close to half of the optical bandgap.In contrast,an electrically heterogeneous microstructure was observed in both the stoichiometric and Na-excess compositions.In addition,the Na-excess compositions exhibited low resistivities(ρ-10^(3)Ω-cm)with characteristic peaks in the impedance data comparable to the recent observations of oxide ion conduction in(Bi_(0.5)Na_(0.5))TiO_(3).Long term annealing studies were also conducted at 800℃to identify changes in crystal structure and electrical properties.The results of this study demonstrates that the dielectric and electrical properties of 0.94(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)ceramics are very sensitive to Bi/Na stoichiometry.展开更多
Charge nonstoichiometric 0.94Bi_(0.5+x)Na_(0.5-x)TiO_(3)-0.06BaTiO_(3)(BNT-BT)(x=-0.02,-0.01,0,0.01,0.02)ceramics were pre-pared and investigated.The depolarization temperature was dependent on composition and the fer...Charge nonstoichiometric 0.94Bi_(0.5+x)Na_(0.5-x)TiO_(3)-0.06BaTiO_(3)(BNT-BT)(x=-0.02,-0.01,0,0.01,0.02)ceramics were pre-pared and investigated.The depolarization temperature was dependent on composition and the ferroelectric property of x>0 was suppressed more significantly than the x<0,indicating the composition-sensitive electrical properties.Furthermore,the x=-0.02 was close to the insulator/conductor composition boundary while the x=0.02 was close to the ferroelectrics/relaxor boundary.These results were attributed to the complex effect of donor doping and acceptor doping on depolarization field.This work provides robust clues to tune and/or design electrical property and conductivity of Bi_(0.5)Na_(0.5)TiO_(3)-based materials.展开更多
文摘Lead free 0.94(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)ceramics were prepared by conventional solid-state mixed oxide route with the A-site stoichiometry modified to incorporate donor-doping(through Bi-excess)and acceptor-doping(through Na-excess).Both stoichiometric and nonstoichiometric ceramics exhibited a single perovskite phase with pseudo-cubic symmetry.A significant improvement in the dielectric properties was observed in Bi-excess compositions and a deterioration in the dielectric properties was observed in Na-excess compositions.Impedance spectroscopy was utilized to analyze the effects of A-site nonstoichiometry on conduction mechanisms.Compositions with Bi-excess resulted in an electrically homogeneous microstructure with an increase in resistivity by3-4 orders of magnitude and an associated activation energy of 1.57 eV which was close to half of the optical bandgap.In contrast,an electrically heterogeneous microstructure was observed in both the stoichiometric and Na-excess compositions.In addition,the Na-excess compositions exhibited low resistivities(ρ-10^(3)Ω-cm)with characteristic peaks in the impedance data comparable to the recent observations of oxide ion conduction in(Bi_(0.5)Na_(0.5))TiO_(3).Long term annealing studies were also conducted at 800℃to identify changes in crystal structure and electrical properties.The results of this study demonstrates that the dielectric and electrical properties of 0.94(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)ceramics are very sensitive to Bi/Na stoichiometry.
基金supported by the State Key Program for Basic Research of China(2015CB921203)the National Nature Science Foundation of China(11674156,51721001,11804150)the“Deng Feng B”of Nanjing University.
文摘Charge nonstoichiometric 0.94Bi_(0.5+x)Na_(0.5-x)TiO_(3)-0.06BaTiO_(3)(BNT-BT)(x=-0.02,-0.01,0,0.01,0.02)ceramics were pre-pared and investigated.The depolarization temperature was dependent on composition and the ferroelectric property of x>0 was suppressed more significantly than the x<0,indicating the composition-sensitive electrical properties.Furthermore,the x=-0.02 was close to the insulator/conductor composition boundary while the x=0.02 was close to the ferroelectrics/relaxor boundary.These results were attributed to the complex effect of donor doping and acceptor doping on depolarization field.This work provides robust clues to tune and/or design electrical property and conductivity of Bi_(0.5)Na_(0.5)TiO_(3)-based materials.
