Fluorite-like compounds with high anionic conductivity in Nd2MoO6 – Bi2O3 system

• Bi2O3-based compounds were found in (Bi2O3)x(Nd2O3)(1−x)/2(MoO3)(1−x)/2 system.
• Cubic δ- Bi2O3 phase is stabilized at 0.67 ≤ x ≤ 0.9.
• Two tetragonal Bi2O3-based phases were found at 0.92 ≤ x ≤ 0.98 and 0.5 ≤ x < 0.6.
• Polymorphism and unit cell behavior of two tetragonal phases are not the same.
• The conductivity of cubic compounds reaches 0.1 S/cm at 800 °C.

A wide range of (Bi2O3)x(Nd2O3)(1−x)/2(MoO3)(1−x)/2 solid solutions with the structure of the anion-conducting bismuth oxide was found in the Bi2O3–Nd2MoO6 join of ternary Bi2O3–MoO3–Nd2O3 system at 0.5 ≤ x ≤ 1. In said concentration range the compounds with large (0.92 ≤ x ≤ 0.98) and small (0.5 ≤ x < 0.6) bismuth content are tetragonal at room temperature. In the intermediate concentration range (0.67 ≤ x ≤ 0.9) cubic δ-Bi2O3 structure is stabilized at room temperature. It is shown that two tetragonal phases observed at different bismuth concentrations differ from each other in their polymorphism and behavior of the unit cell parameters. All the obtained compounds show high conductivity that reaches 0.1 S/cm (for a cubic sample with x = 0.8 at 800 °C).