Enhancement of the Ionic Conductivity in Electric Field-Assisted Pressureless Sintered BITIVOX Solid Electrolytes

Abstract

Bi 4 V 1.8 Ti 0.2 O 11 (BITIVOX) ceramic pellets, prepared with powders obtained by a sol gel technique, were sintered either conventionally at 800 • C/8 h or by applying an AC electric voltage, limiting the electric current through the pellets. Electric voltages were applied isothermally at 700 • C and 800 • C during 5 min in the green pellet positioned in the sample holder of a dilatometer for monitoring thickness variation. The BITIVOX pellets shrank 13.6% after applying 200 V cm −1 at 800 • C and 10.4% heating to 800 • C for 8 h. Thermal analysis and X-ray diffraction of the powders were performed to evaluate the crystallization temperature and the structural phase, respectively. The electrical behavior of the sintered BITIVOX pellets was analyzed by the impedance spectroscopy technique, showing that the sample flash sintered at 800 • C/5 min had lower bulk resistivity than the sample conventionally sintered at 800 • C/8 h. The surfaces of the sintered pellets were observed in a scanning electron microscope showing similar grain sizes and pore content in all sintered samples.

Sol-gel Synthesis and Characterization of MgCO3 – Al2O3 Composite Solid Electrolytes

“…From Figure 11, the Rb values for example for x = 0.7, 0.8 and 0.9 ratio increased as the temperature increased up to certain temperature before going down as the temperature rises up. Other solid composite electrolytes have been reported to undergo the same phenomenon in lowering the electrical resistivity as the temperature increase due to increasing Joule heating, thus forming high dense pellet which could probably lead to higher conductivity [53,54]. The temperature dependence of conductivity can be obtained by Arrhenius equation of σ = A exp (Ea/RT) where A is the pre-exponential factor, Ea is the activation energy (eV) while k is the Boltzmann's constant with the value of 8.52 × 10 -5 eV/K and T is the temperature (K).…”

“…The formation of agglomerated structure might provide better charge/discharge capacity due to excellent trap density that shortens the diffusion of Mg 2+ ion [34,35]. Moreover, calcination of the composite at such a high temperature would be able to reduce the electrical resistivity, induce Joule heating, producing more compact and dense structure of composite leading to possibility of higher conductivity [36]. In addition, the formation of all the expected elements namely Mg, Al and O can be found in good agreement between each other as indicated by EDS analysis from two different spots in Figure 6 which further confirm the uniform dispersion of MgO particles.…”