Effect of A and B-site ion doping on the structure and properties of KNN-based ceramic coatings

K 0.5 Na 0.5 NbO 3 (KNN) ceramics have been widely studied for high Curie temperature ( T c ) and good electrical properties. The structural and electrical properties of KNN ceramics were significantly improved by A-site and B-site doping modifications. In this paper, KNN-based ceramic coatings doped with Mn, and Sb were prepared by supersonic plasma spraying. The effects of doping ions at A-site and B-site on the microstructure, phase structure, mechanical properties, and electrical properties of KNN-based ceramic coatings were mainly analyzed. The results show that the surface of the three coatings KNN, K 0.5 Na 0.5 Nb 0.94 Sb 0.06 O 3 (KNNS), and K 0.49 Na 0.49 Mn 0.02 NbO 3 (KNMN) is relatively flat, uniform distribution of the elements. The surface roughness (Sa) is 3.85 μm, 3.88 μm, and 3.66 μm, respectively. Pores and cracks are present within the coatings, but the KNNS ceramic coatings have significantly fewer pores and cracks compared to the KNN and KNMN ceramic coatings. XRD results show that KNN-based ceramic coatings exhibit single perovskite structure, and both Mn and Sb are successfully introduced into the KNN ceramics without the generation of a second phase. XPS results showed that the valence states of the elements in the KNN ceramic coatings did not change. In KNMN and KNNS ceramic coatings, the valence state of the doped elements did not change. The addition of Mn 2+ and Sb 3+ reduced the oxygen vacancy in KNN ceramic coatings. Among them, the KNMN ceramic coatings microhardness increased by 45.3 HV 0.2, remnant polarization ( P r ) increased by 8.1 μC/cm 2, the dielectric constant ( ε r ) increased by 107, and dielectric loss greatly reduced, reaching 0.005. The KNMN ceramic coatings microhardness increased by 90.8 HV 0.2, dielectric constant increased by 195, P r increased by 16.7 μC/cm 2, dielectric loss is 0.007. These findings demonstrate that doping with Mn 2+ and Sb 3+ has a positive impact on the performance of KNN ceramic coatings, with Sb 3+ having a greater effect.