With flexibility, tunability and dual-ion transport, double-perovskites are promising dual-ion electrolytes in solid-oxide fuel-cells (SOFCs). Density-functional theory investigated structural, electronic, dielectric and defect properties for Ba₂ZnInO₆, Ba₂TaBiO₆, Ba₂NbBiO₆ and Ba₂ScNbO₆. Optimized systems were thermodynamically stable, with tolerance factors ranging 0.93-0.98. Calculated band gaps (2.8–4.1 eV) ensured sufficient insulation, while dielectric constants (25–38) indicated strong polarization-defect formation and ion migration, with distinct transport characteristics. Ba₂ZnInO₆ was dominantly p-type, with electronic-transport-coefficient (σ/τ) 2.48×10²⁰ S/m·s. Ba₂TaBiO₆ exhibited bipolar conduction. Ba₂NbBiO₆ presented mixed but favourably n-type. Ba₂ScNbO₆ was stable n-type with σ/τ 3.85×10²⁰ S/m·s. Dielectric (ε) screening and defect-energetic correlation confirmed lower oxygen vacancy and proton formation energies (<1.5 eV) for higher ε materials, promoting enhanced ionic mobility. Ba₂ScNbO₆ showed highest balanced combination of wide-band gap, high dielectric constant and low defect formation-energy, being suitable for dual-ion-conducting electrolytes. Elucidated dielectric-controlled defect mechanisms help in future low-cost SOFC key-design principles and experimental studies.

Title

Chemical Physics

Publisher

Elsevier

Publisher Country

Netherlands

Indexing

Thomson Reuters

Impact Factor

2.4

Publication Type

Both (Printed and Online)

Volume

--

Year

2026

Pages

113126