Spectroscopic study of Co-doped CaCu3Ti4O12

Calcium-copper titanate has been thoroughly studied by scientists around the world for several decades due to the manifestation of colossal dielectric permeability values (ε ~104 –105) in wide frequency ranges (102 –106 Hz) and temperature ranges (100 – 600 K), showing neither ferroelectric nor relaxor properties. Due to the unique dielectric characteristics of calcium-copper titanate (CCTO), materials based on it are promising for the manufacture of multilayer capacitors and microwave devices. Restrictions on the practical use of CCTO are caused by high dielectric losses. Electrophysical characteristics are optimized by modifying the CCTO composition, partially replacing copper, titanium and calcium cations. Good dielectric properties are demonstrated by the CCTO ceramics doped with cobalt atoms. Co-doped CaCu3Ti4O12 was obtained by solid phase synthesis method. The samples are characterized by a grain microstructure; a thin layer of CuO is fixed in the intergranular space. From the interpretation of the obtained XPS- and NEXAFS 2p-spectra of Co-doped CaCu3Ti4O12 and the corresponding oxides it can be concluded that in the Co-doped ССТО atoms of copper and calcium have a charge state of +2, atoms of titanium — +(4 − δ), and cobalt atoms mainly +2 with some fraction of Co (III) in the high spin state. The Co-doped sample FTIR spectrum clearly captures the absorption bands in the fingerprint area at ≈408, 488, 539 cm−1, which are typical for ССТО.

Kinetics of the formation of diffusion titanium coatings on the surfaces of hard alloys during isothermal mass transfer of titanium in the Pb-Bi-Li melt

E.E. Bobylyov, E.G. Sokolov