Optical, mechanical and TEM assessment of titania-doped Bi2V1−x Ti x O5⋅5−δ bismuth vanadate oxides

Abstract

Optical, mechanical and structural behaviors have been studied for titania-doped Bi 2 V 1−x Ti x O 5•5−δ which are used as electrolytes for intermediate temperature fuel cells. Parameters like band gap (E g), Urbach energy (E u), refractive index, hardness (H) and fracture strength (K) have been calculated as a function of dopant concentration, i.e. 0•05 ≤ x ≤ 0•2. Furthermore, analysis of transmission electron microscopy (TEM) images for all the oxides was conducted along with line spectra of planes. Results are discussed in light of correlation of these optical and mechanical parameters to their structural properties. Band gap has also been correlated to the conductivity of these oxides. Good correlation has been obtained between them.

Role of Al and Ti doping in modulating electrical properties of BIVOX system

“…The exponent n is an index whose value characterizes the optical absorption process. n = 1/2 and n = 2 denote direct allowed and indirect allowed transitions, respectively, while n = 3/2 and n = 3 are for direct forbidden and indirect forbidden transitions, respectively [37]. Further, the obtained diffuse reflectance spectra have been converted into Kubelka-Munk function by introducing the quantity F(R∞) (proportional to α).…”

“…It has been observed that doping of Al and Ti at V-site results in the blue shift of direct band gap of all the doped samples. Kaur et al [37] have studied the Ti III -doped BIVOX system and have correlated the smaller band gap of the material with the higher conductivity due to optimization of the oxygen vacancies concentration located on equatorial lines of the perovskite layers (VO 3.5 ) 2− . Similarly, in the present system, the observed lowest value of E g for the composition x = 0.175 (even compared to parent compound) can be correlated to the presence of comparatively higher order of oxide ion vacancies than other prepared compositions.…”