We used XPS technology to further i

We used XPS technology to further investigate the chemical composition and bonding at the particle surface of the uncoated and the coated powders 1-5, 2-5, and 3-5. Fig. 4–7 shows the high-resolution spectra of individual elements Ba3d, Ti2p, O1s, and C1s, respectively. Fig. 4(a–4(d) show the Ba 3d photoelectron spectra of the BaTiO3 powders and the coated powders 1-5, 2-5, and 3-5, respectively. The Ba3d spectrum consists of two peaks, one at 778.82 eV and one at 794.12 eV, which are identified with the Ba-O bond, whereas the two subpeaks Ba3d5/2 (777.93 eV) and Ba3d3/2 (793.15 eV) are identified with BaCO3 and/or the relaxed Ba phase and are probably caused by oxygen vacancies and other residual defects [24, 25].