Abstract:
Recently it has been reported that low levels of Bi nonstoichiometry (only plus or minus 1 atomic percent) in the nominal starting composition of Na sub(0.5) Bi sub(0.5) TiO sub(3) (NBT) ceramics can lead to dramatic changes in the conduction property. Present article present the results of powder XRD, sup(23) Na MAS NMR and impedance spectroscopy in nominal starting compositions, Na sub(0.5) Bi sub(0.5+x) TiO sub(3+3x/2) with x = 0.0 and - 0.02. Room temperature XRD data analysis indicates both NBTs have a rhombohedral (space group R3c) structure. While, sup(23) Na MAS NMR results demonstrate a complex local structure and significant disordering of Na coordination environment. Impedance spectroscopy reveals high levels of oxide-ion conduction in NBT. 2 at- percent Bi-deficient NBT (Na sub(0.5) Bi sub(0.48) TiO sub(2.97)) exhibits higher conductivity of sigma approx. 1.3 x 10-4 S/cm at 500 degrees C and activation energy, Ea = 0.85 eV. Present results therefore substantiate the A-site nonstoichiometry sensitive electrical property of NBT.
