There were at least 2 conductivity maxima in the Ln2O3–TiO2 (Ln = Ho–Lu) systems. High oxide-ion conductivity was typically offered by stoichiometric or near-stoichiometric Ln2+xTi2−xO7−δ (Ln = Ho–Lu; x = 0 to 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 was lower than that of the Ln2+xTi2−xO7−δ (Ln = Er–Lu; x = 0 to 0.096) pyrochlores; similar to that reported for the Y2O3–TiO2 system.

Heavily Doped Oxygen-Ion Conducting Ln2+xTi2−xO7−δ (Ln = Ho–Lu; x = 0.44–0.81) Pyrochlores - Crystal Structure, Microstructure and Electrical Conductivity. A.V.Shlyakhtina, S.N.Savvin, A.V.Levchenko, M.V.Boguslavskii, L.G.Shcherbakova: Solid State Ionics, 2008, 179[21-26], 985-90