From insulator to oxide-ion conductor by a synergistic effect from defect chemistry and microstructure: acceptor-doped Bi-excess sodium bismuth titanate Na_0.5Bi_0.51TiO_3.015

Abstract

Low levels of acceptor-type dopants can introduce appreciable levels of oxide-ion conductivity into NB0.51T due to a synergistic effect from defect chemistry and ceramic microstructure.

Associating High Oxide-Ion Conductivity and Conduction Mechanisms with Local Atomic Environments in Na0.5Bi0.5–xTi1–yMgyO3−δ

“…The SEM micrographs (Figure ) display much larger average grain size in NBTM1 (13 μm) and NBTM2 (10 μm) compared to that of NBT (3.5 μm). The average grain size in NBTM1 and NBTM2 samples were found to be larger than the critical size of 3.5 μm: the value of critical grain size has been estimated by Yang et al from the conductivity vs. grain size plot for stoichiometric and non-stoichiometric NBT materials. Earlier, a similar grain size distribution has been reported for NBT and NBTM1 composition. , This noticeably larger grain size and tight packing of grains in NBTM1 and NBTM2 samples are expected to result much lower grain boundary resistance and, in turn, higher σ gb .…”

“…This result demonstrates a remarkable influence of non-stoichiometry on the electrical conductivity. Moreover, the electrical conductivity of NBTM1 ceramic is only due to the diffusion of oxide ions, verified by 18 O/ 16 O tracer diffusion measurements 8 and calculation of mean square displacement (MSD) of cations as a function of time at high temperatures. 17 comparable to the other well-known oxide-ion conductors, 18,19 s u c h a s Z r 0 .…”

“…The electrical conductivity of NBT is low at RT. However, high electrical conductivities have been reported in nominally Bi-deficient/Na-excess and Ti-site acceptor-doped NBT compositions. − Among them, the NBT ceramic with 1 at. % Bi-deficient, 2 at.…”

Electrical conductivity and oxygen relaxation behavior in BaBi1−xSrxNb5O15−δ tungsten bronze ceramics

“…Besides adjusting the nonstoichiometric ratio of Bi 3+ , acceptor doping is another effective way to introduce oxygen vacancies into BBN compounds. 16 In our previous work, the BaBi 0.96 Na 0.04 Nb 5 O 15−δ compound exhibited a total conductivity of 1.12 × 10 −4 S cm −1 at 643 K, almost three times as high as the pristine BBN material at the same temperature. 17 The research concludes that low-valent ion doping is a feasible strategy to ameliorate the properties of the BBN compound.…”

Investigation of Ga doping for non-stoichiometric sodium bismuth titanate ceramics

“…To get the higher electrical properties in the NBT based oxygen ion conductors, higher oxygen vacancy content is necessary. There are two ways to introduce oxygen vacancies into NBT compound: Bi-deficiency and acceptor doping [10]. According to Li Ming et al results [6], the ionic conductivity can be greatly improved through introducing a low-level non-stoichiometric defect(<1 at.%) in NBT [1,7].…”