Heavily doped oxygen-ion conducting Ln2 + xTi2 − xO7 − δ (Ln = Ho–Lu; x = 0.44–0.81) pyrochlores: Crystal structure, microstructure and electrical conductivity

There are at least two conductivity maxima in the Ln2O3–TiO2 (Ln = Ho–Lu) systems. High oxide-ion conductivity is typically offered by stoichiometric or near-stoichiometric Ln2 + xTi2 − xO7 − δ (Ln = Ho–Lu; x = 0–0.096) pyrochlores and heavily doped, disordered Ho2 + xTi2 − xO7 − δ (0.48 ≤ x ≤ 0.67) pyrochlores just near the boundary of the continuous P → F phase transition. The conductivity of the fluorite-like Ln2 + xTi2 − xO7 − δ (Ln = Er–Lu; 0.63–0.74) solid solutions is lower than that of the Ln2 + xTi2 − xO7 − δ (Ln = Er–Lu; x = 0–0.096) pyrochlores, similar to what was reported for the Y2O3–TiO2 system.