TY - JOUR

T1 - Magnetic susceptibility, XPS and NEXAFS spectroscopy of Ni-doped CaCu3Ti4O12 ceramics

AU - Zhuk, N. A.

AU - Nekipelov, S. V.

AU - Sivkov, V. N.

AU - Makeev, B. A.

AU - Korolev, R. I.

AU - Belyy, V. A.

AU - Krzhizhanovskaya, M. G.

AU - Ignatova, M. M.

N1 - Funding Information: The authors thank Sekushin N.A. (Institute of Chemistry of the Komi Science Center UB RAS) for their help in studying the dielectric properties of the samples of CaCu3Ti4-4xNi4xO12-? and CaCu3-3xNi3xTi4O12. The authors acknowledge the Research Center of X-ray diffraction Studies of St. Petersburg State University for computational resources.

PY - 2020/9/15

Y1 - 2020/9/15

N2 - Two series of Ni-doped CaCu3Ti4O12 ceramics with CaCu3Ti4-4хNi4хO12-δ and CaCu3-3хNi3хTi4O12 compositions were obtained by the solid-phase synthesis method. The magnetic behavior of the samples in the range of 77–400 K was studied by magnetic dilution. For the first time the samples of both series were characterized by the spectroscopic methods: XPS and NEXAFS. As a result of XPS spectroscopy, it was found that calcium, copper and nickel atoms mainly have the oxidation state (II), and titanium atoms can exhibit oxidation states of (III) and (IV). NEXAFS-study of Ni-doped CCTO showed that titanium atoms mainly have the oxidation state (IV). In the NEXAFS spectra of nickel of the both series of the samples, a feature associated with the presence of Ni(II) in the square-planar environment was manifested. It was concluded that nickel atoms were distributed in the positions of copper and titanium in the samples of both series. The magnetic behavior of the nickel-doped solid solutions of both types of substitution was different only at x ≥ 0.03, which indicated the advantage of placing nickel (II) atoms in the Cu(II) position. According to the magnetic dilution data, the antiferromagnetic exchange was realized between the nearest paramagnetic nickel atoms in CaCu3Ti4-4хNi4хO12-δ and the ferromagnetic one between the paramagnetic clusters.

AB - Two series of Ni-doped CaCu3Ti4O12 ceramics with CaCu3Ti4-4хNi4хO12-δ and CaCu3-3хNi3хTi4O12 compositions were obtained by the solid-phase synthesis method. The magnetic behavior of the samples in the range of 77–400 K was studied by magnetic dilution. For the first time the samples of both series were characterized by the spectroscopic methods: XPS and NEXAFS. As a result of XPS spectroscopy, it was found that calcium, copper and nickel atoms mainly have the oxidation state (II), and titanium atoms can exhibit oxidation states of (III) and (IV). NEXAFS-study of Ni-doped CCTO showed that titanium atoms mainly have the oxidation state (IV). In the NEXAFS spectra of nickel of the both series of the samples, a feature associated with the presence of Ni(II) in the square-planar environment was manifested. It was concluded that nickel atoms were distributed in the positions of copper and titanium in the samples of both series. The magnetic behavior of the nickel-doped solid solutions of both types of substitution was different only at x ≥ 0.03, which indicated the advantage of placing nickel (II) atoms in the Cu(II) position. According to the magnetic dilution data, the antiferromagnetic exchange was realized between the nearest paramagnetic nickel atoms in CaCu3Ti4-4хNi4хO12-δ and the ferromagnetic one between the paramagnetic clusters.

KW - Calcium-copper titanate

KW - Magnetic properties

KW - XPS and NEXAFS spectroscopy

UR - http://www.scopus.com/inward/record.url?scp=85086638496&partnerID=8YFLogxK

U2 - 10.1016/j.matchemphys.2020.123310

DO - 10.1016/j.matchemphys.2020.123310

M3 - Article

AN - SCOPUS:85086638496

VL - 252

JO - Materials Chemistry and Physics

JF - Materials Chemistry and Physics

SN - 0254-0584

M1 - 123310

ER -