Investigation of electrical properties for Ca-modified BaBiNb5O15 compound

BaBiNb ₅ O ₁₅ , a tungsten bronze-structured oxygen ion conductor, shows great promise for medium-temperature solid oxide fuel cells due to its excellent electrical conductivity and thermal stability. The effects of Ca ²⁺ ion doping on the structural, microstructural, and electrical conductivity characteristics of the BaBiNb _5 − x Ca _x O _15−δ compounds were analyzed. Measurements using AC impedance spectroscopy revealed that at 773 K, the grain conductivity of BaBi _0.95 Ca _0.05 Nb₅O _15−δ sample can reach 3.79×10 ^− 4 S/cm, representing an approximate 5.1-fold increase compared to the undoped BaBiNb ₅ O ₁₅ compound. Dielectric modulus analysis identified an activation energy of 0.37 eV for oxygen ion diffusion, with relaxation parameters indicating that dielectric loss peaks originate from vacancy-mediated oxide ion motion in the BaBi _0.95 Ca _0.05 Nb ₅ O _15−δ sample. The enhanced ionic conductivity arises from increased mobile oxygen vacancy density, improved mobility, lower activation energy, and reduced relaxation time. These findings elucidate the mechanism of oxygen vacancy diffusion and the origin of oxygen relaxation behavior in BaBiNb ₅ O ₁₅ compound, advancing fundamental understanding of oxygen ion conductor characteristics while guiding future investigations into the electrical properties of BaBiNb ₅ O ₁₅ -based materials.