γ-Phase stabilized Bi4BaxV2−xO11−δ (0.0 ≤ x ≤ 0.20): Structural, thermal and conducting properties

Structural, optical, thermal and conducting properties of V2−xLixO5−δ (0.15 ≤ x ≤ 0.30) systems

“…Since, the high operating temperature of SOFC leads to degradation, coefficient of thermal expansion mismatch, electrode sintering and catalyst poisoning among the components of SOFCs [1][2][3] . Thus, a lot of research is carried out to develop new materials that can meet the requirements at lower operating temperature of SOFCs [3][4][5] . Doped V 2 O 5 materials can be a good choice for low temperature (600-800 °C) SOFCs applications due to their good conductivity at lower temperature 6 .…”

“…Alkali metal oxide doped vanadates have been studied widely due to their numerous applications in optical and electronic devices 1,2,8 . The chemical nature and concentration of dopants play a vital role to change the oxidation state of vanadium which leads to a creation of oxygen vacancies to maintain overall electrical neutrality of the vanadate systems 5,9,10 . Punia et al have reported the increasing trend of density and molar volume due to change in structure from VO 4 tetrahedral to VO 5 trigonal bi-pyramid with the addition of Bi 2 O 3 in zinc vanadates 11 .…”

“…Tsuzuki et al 16 have investigated V 2 O 5 -MO (M = Mg, Ca and Ba) systems and correlate the structural changes with electrical properties. In most of the cases, these doped systems are prepared by solid-state reaction/chemical method followed by slow cooling which leads to lower the conductivity due to ordering in oxygen vacancies 5 . It has been reported by some research groups that quenched samples have higher disordering/defects which leads to increase in the overall electrical conductivity.…”

“…It has been reported by some research groups that quenched samples have higher disordering/defects which leads to increase in the overall electrical conductivity. The high quenching rate encourages the reduction of vanadium which leads to higher disordering and hence may increase the overall conductivity 5,17 . Based on above discussion, it could be concluded that processing parameters and chemical nature of dopants affect the properties significantly particularly conductivity.…”

“…On the replacement of V 5+ by Li + , structure of the systems becomes more open due to transition from VO 4 tetrahedral to VO 5 trigonal bipyramid as discussed in physical parameters and structural properties. This structural change is responsible for a significant increase in oxygen vacancies with an increase in hopping of ions which leads to an increase in conductivity 4,5,42 . In addition, decrement in density, inter-ionic distance, polaron radius and optical band gap of the samples also support this increasing trend of conductivity with the addition of Li 2 O It is observed that the transport mechanism in lithium vanadate systems is attributed to small polaron hopping (SPH) between V 4+ to V 5+ states, which is increased by the addition of lithium into vanadium.…”