Oxide ion distribution and conductivity in Bi7Nb2−2xY2xO15.5−2x

Investigation of transport numbers in yttrium doped bismuth niobates

“…5.5 Å in space group Fm3m. It should be noted that neutron diffraction studies on the Bi 3.5 Nb 1−x Y x O 7.75−x system revealed that niobiumrich compositions (x ≤ 0.2) show superlattice reflections, consistent with a Type-II incommensurately ordered phase and therefore these phases are technically pseudo-cubic, whereas for higher values of x a fully disordered ␦-Bi 2 O 3 type cubic phase is observed [10]. Impedance spectra for Bi 3.5 NbO 7.75 at low temperatures (Fig.…”

“…A double substitution approach can be adopted to increase vacancy concentration and hence ionic conductivity. We have investigated double substitution in Bi 2 O 3 in the Bi 2 O 3 -Y 2 O 3 -Nb 2 O 5 ternary system with detailed structural and electrical investigations of the pseudo-binary systems Bi 3 YO 6 -Bi 3 NbO 7 [9] and Bi 3.5 YO 6.75 -Bi 3.5 NbO 7.75 [10]. Both these systems exhibit full solid solution ranges, with a fluorite type structure maintained throughout.…”

Structural and transport characteristics of substituted bismuth niobates

“…However, the situation is changed to the opposite at an increase in the amount of the dopant in the case of Bi 2.95 Y 0.05 Nb 1 -y Zr y O 7 ± δ . A transition into the region with lower activation energy is observed for samples with y ≥ 0.2 at high temperatures, which is possibly due to the temperature dependence of oxygen distribution across the 8c and 32f sites of the crystalline structure [10]. As follows from Fig.…”

“…4-6, Table 3). The general run of temperature dependences of conductiv ity for the studied solid solutions has the shape typical for the cubic modification of bismuth niobate [8][9][10]. Two linear regions can be distinguished in the depen dences.…”

“…Doping by yttrium or an increase in the ratio of Bi : Nb in niobates result in a decrease in the contribution of electronic conductiv ity. In the case of samples of the Bi 7 Nb 2 -x Y 2x O 15.5 -x (0.0 ≤ x ≤ 0.1) system with high yttrium content, a transition into the region with a lower activation energy is observed at high temperatures [10]. The authors explain this by the temperature dependence of oxygen distribution across the 8c and 32f sites of the crystalline structure.…”