TY  - JOUR
AU  - Savvin, S.N.
AU  - Avdeev, M.
AU  - Kolbanev, I.V.
AU  - Kharitonova, E.P.
AU  - Shcherbakova, L.G.
AU  - Shlyakhtina, A.V.
AU  - Nuñez, P.
T1  - Stability against reduction of fluorite-like rhombohedral La5.5MoO11.25 and Ho5.4Zr0.6MoO12.3 fluorite: Conductivity and neutron diffraction study
LA  - eng
PY  - 2018
SP  - 148
EP  - 155
T2  - Solid State Ionics
SN  - 0167-2738
VL  - 319
PB  - Elsevier B.V.
AB  - Zr-substituted rare-earth molybdates Ho5.4Zr0.6MoO12.3 and unsubstituted La5.5MoO11.25 demonstrate appreciable mixed electron-proton conductivity in the 200–470 °C and 145–730 °C temperature range, respectively, under wet oxidizing and mild reducing conditions (air, Ar, Ar-5% H2). Rhombohedral fluorite-like La5.5MoO11.25 showed the highest bulk conductivity of about 1 × 10−5 S/cm at 400 °C in wet air and Ar. Its impedance spectra did not provide any evidence of the grain boundary contribution in wet atmosphere. Total conductivity of Ho5.4Zr0.6MoO12.3 fluorite is much lower and is 3 × 10−7 S/cm at 400 °C in wet air. Besides, it should be noted that there is a grain-boundary contribution of Ho5.4Zr0.6MoO12.3 in wet air and Ar. Thermogravimetry data demonstrate that the fraction of strong structurally bound water and interstitial protons in La5.5MoO11.25 and Ho5.4Zr0.6MoO12.3 is ~0.02–0.03% in the range ~600–900 °C. The stability of Ho5.4Zr0.6MoO12.3 fluorite structure and fluorite-like rhombohedral La5.5MoO11.25 structure in extremely dry conditions under dynamic vacuum of 10−6–10−7 mbar was investigated by in situ variable temperature neutron diffraction between 800 and 1400 °C to understand phase behaviour under mild reducing conditions in a wide temperature range. Rhombohedral fluorite-like La5.5MoO11.25 has been shown to be more resistant to reduction under vacuum below 1100 °С in heating–cooling cycles than is fluorite Ho5.4Zr0.6MoO12.3. Given the higher proton conductivity of Ln5.5MoO11.25, this suggests that rhombohedral fluorite-like La6MoO12 - based molybdates are suitable for long-term use under mild reducing conditions and 600–800 °С.
DO  - 10.1016/j.ssi.2018.02.001
UR  - https://portalciencia.ull.es/documentos/5e3c3eb629995246bbf612e9
DP  - Dialnet - Portal de la Investigación
ER  -