ABO 3−ξ -type oxides have gained prominence because of their usefulness in gas separation, solid oxide fuel cell, gas sensor, etc. Of particular interest is barium and zinc substituted strontium ferrite – an alternative cathode material due to its high structural stability, accommodation of considerable anion deficiency, and good oxygen permeability. An attempt has therefore been made to synthesize Ba 0.5 Sr 0.5 Zn 0.2 Fe 0.8 O 3−ξ powder by a novel oxalate sol–gel route to investigate its formation, nature of iron species, optical absorption, and impedance behaviour. The synthesis process involves gel formation, digestion for 6h, drying at 150 °C for 24h, and decomposition of oxalate at 950 °C for 15h in air. The product is shown to exhibit (i) a perovskite-type cubic phase with a = 3.975 ± 0.002Å, Z = 1, and space group Pm3m, (ii) Fe 3+ 0.5 and Fe 4+ 0.3 ions, (iii) oxygen deficiency parameter ξ ∼ 0.45, and (iv) optical absorption at ∼370 nm (∼3.4 eV) and ∼797 nm (∼1.56 eV) – arising due to charge transfer transition from O 2− (2p) to Fe 3+ (3d) and octahedral crystal field splitting of iron t 2g and e g orbitals, respectively. Moreover, the high impedance values observed below 10 kHz over a temperature range of 303–413K have been attributed to space charge polarization; activation energy of the relaxation process being 0.2eV. The motion of induced polarons is possibly responsible for the decrease of impedance with increase of temperature in the range 303–413K.