摘要： The room-temperature multiferroic behavior of cobalt-substituted KNN [K0.5Na0.5Nb1?xCoxO3, 0.02 ≤ x ≤ 0.05] ceramics has been investigated. Both the X-ray diffraction and selected area electron diffraction analysis confirm that all the compositions found to be crystallized in the single phase (Orthorhombic, Amm2) without any formation of cobalt clusters and/or other secondary phases such as Co3O4. Co2+ oxidation state and the presence of oxygen vacancies in the samples have been studied through X-ray photoelectron spectroscopic measurements. The changes in the bandgap with the increase of Co concentration in KNN are noticed from UV–Visible absorption spectroscopy. Magnetic measurement on the samples reveals a dominant antiferromagnetic interaction attributed to the Co2+–Co2+ exchange interactions via F0-center and coupling between Co2+–Co2+ through O2?. The existence of exchange bias (EB) effect is also observed in KNaNb1?xCoxO3 (x = 0.03, 0.04, 0.05) samples from the magnetic measurements. In addition, it is found that defect complexes formed between Co′′′ Nb and oxygen vacancy lead to the enhanced dielectric, ferro, and piezoelectric properties of K0.5Na0.5Nb1?xCoxO3 ceramics.