Ag 2 Mo 2 O 7 : an oxide solid-state Ag + electrolyte.

Ag 2 Mo 2 O 7 powders and micro-crystals were prepared at 400 °C for 24 h and 500 °C for 6 h using solid-state reactions. The Ag 2 Mo 2 O 7 samples crystalized in a triclinic P 1̄ space group with the cell parameters a = 6.0972(1) Å, b = 7.5073(1) Å, c = 7.6779(2) Å, α = 110.43(1)°, β = 93.17(1)°, γ = 113.51(1)°, and V = 294.17(1) Å 3 from Rietveld refinements. Ag 2 Mo 2 O 7 powder is homogeneous with size of 2-8 μm and the ceramic pellets are in good sintering conditions with a relative density ∼93%. The indirect band gaps E g (i) of Ag 2 Mo 2 O 7 from reflectance measurements and DFT calculations are 2.63(1) and 1.80 eV. The vibrational modes of Ag 2 Mo 2 O 7 were investigated by first-principles (DFT) calculations and Raman spectrum measurements with 24 of 33 predicted Raman modes recorded. According to DOS analyses, the valence bands (VB) of Ag 2 Mo 2 O 7 are mainly constituted of O-2p and Ag-4d orbitals, while the conduction bands (CB) are mainly composed of Mo-4d and the O-2p orbitals. Regarding the impedance analysis, Ag 2 Mo 2 O 7 is a silver oxide ion electrolyte with a conductivity of ∼5 × 10 -4 S cm -1 at 450 °C. The carrier activation energy of Ag 2 Mo 2 O 7 is 0.88(3) eV from the temperature dependent conductivity measurements.