TY - JOUR

T1 - Proton /oxygen ion conductivity ratio of Nd containing La10W2O21/γ-La6W2O15 tungstates

AU - Shlyakhtina, A.

AU - Baldin, Egor D.

AU - Vorobieva, G.

AU - Kolbanev, I.

AU - Stolbov, D.

AU - Kasyanova, A.

AU - Lyskov, N.

N1 - The support of this work from Russian Foundation for Basic Research (Project 20-03-00399) is gratefully acknowledged. The work was supported partially by the subsidy from the Ministry of Education and Science allocated by the FRC CP RAS for the implementation of the state assignment (No.122040500071-0, No. 122040500068-0) and in accordance with the state task for FRC PCP and MC RAS, state registration No. АААА-А19-119061890019-5. L.N.V. acknowledges the project of the HSE Scientific and Educational Group (No. 962581). The authors are grateful to A. N. Shchegolikhin for measurements of Raman spectra.

PY - 2023/7/1

Y1 - 2023/7/1

N2 - The search for new materials with pronounced proton or oxygen-ion conductivities is of great importance for the development of solid state ionic and electrochemistry fields. Here, we studied the structure, phase transitions, and ionic (oxygen-ion and proton) conductivity of the pure and Nd containing γ-La6W2O15-based composites and pseudorhombohedral La14-xNdxW4O33 (x = 12, 14) solid solutions. The proton conductor La14W4O33 (5 × 10−5 S/cm at 600 °C) was found to be a two-phase material consisting of an anion-deficient La10W2O21 fluorite-related phase and the γ-La6W2O15 orthorhombic phase. The phase content of the pure La10W2O21 cubic phase was ∼18 wt% for the γ-La6W2O15-based composite. A high degree of Nd content in γ-La6W2O15-based composite leads to formation of solid solutions based on a pseudorhombohedral phase in La14-xNdxW4O33 with x = 12 and 14. The Nd -containing γ-La6W2O15-based composites exhibited proton conductivity, which gradually decreased with increasing Nd content, whereas La14-xNdxW4O33 (x = 12, 14) pseudorhombohedral solid solutions were identified as oxygen-ion conductors. Nd14W4O33 has the oxygen -ion conductivity of ∼4 × 10−4 S/cm at 700 °C (1.0 × 10−3 S/cm at 900 °C). In contrast to the γ-La6W2O15 phase, the γ-La6W2O15-based composite undergoes only a single reversible phase transition at around 910 °C, which can, however, initiate cracks in ceramics. According to DSC and SEM data, the phase transition near 910 °C can be suppressed by introducing Nd into the γ-La6W2O15-based composites. The cracking process is enhanced by evaporation of tungsten oxide at T ≥ 1450 °C.

AB - The search for new materials with pronounced proton or oxygen-ion conductivities is of great importance for the development of solid state ionic and electrochemistry fields. Here, we studied the structure, phase transitions, and ionic (oxygen-ion and proton) conductivity of the pure and Nd containing γ-La6W2O15-based composites and pseudorhombohedral La14-xNdxW4O33 (x = 12, 14) solid solutions. The proton conductor La14W4O33 (5 × 10−5 S/cm at 600 °C) was found to be a two-phase material consisting of an anion-deficient La10W2O21 fluorite-related phase and the γ-La6W2O15 orthorhombic phase. The phase content of the pure La10W2O21 cubic phase was ∼18 wt% for the γ-La6W2O15-based composite. A high degree of Nd content in γ-La6W2O15-based composite leads to formation of solid solutions based on a pseudorhombohedral phase in La14-xNdxW4O33 with x = 12 and 14. The Nd -containing γ-La6W2O15-based composites exhibited proton conductivity, which gradually decreased with increasing Nd content, whereas La14-xNdxW4O33 (x = 12, 14) pseudorhombohedral solid solutions were identified as oxygen-ion conductors. Nd14W4O33 has the oxygen -ion conductivity of ∼4 × 10−4 S/cm at 700 °C (1.0 × 10−3 S/cm at 900 °C). In contrast to the γ-La6W2O15 phase, the γ-La6W2O15-based composite undergoes only a single reversible phase transition at around 910 °C, which can, however, initiate cracks in ceramics. According to DSC and SEM data, the phase transition near 910 °C can be suppressed by introducing Nd into the γ-La6W2O15-based composites. The cracking process is enhanced by evaporation of tungsten oxide at T ≥ 1450 °C.

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U2 - 10.1016/j.ijhydene.2023.03.259

DO - 10.1016/j.ijhydene.2023.03.259

M3 - Article

VL - 48

SP - 22671

EP - 22684

JO - International Journal of Hydrogen Energy

JF - International Journal of Hydrogen Energy

SN - 0360-3199

IS - 59

ER -