Metal-insulator transition in Ni-doped Na0.75CoO2: Insights from infrared studies

Premila, M.; Bharathi, A.; Gayathri, N.; Yasodha, P.; Hariharan, Y.; Sundar, C. S.

doi:10.1007/s12043-006-0046-5

Cited by 6 publications

(3 citation statements)

References 18 publications

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“…In the spectral area of 400 -600 cm −1 valence oscillations of Co-O appear. According to the literature, at 548 -570 cm −1 the absorption band of valence oscillations of Co (III)-O bond is fixed in the octahedron CoO 6 [38], and in the region 653 -663 cm −1 the band is responsible for oscillations of Co (II)-O bond in the tetrahedron CoO 4 . In the spectrum of compounds, the frequency range of 400 -600 cm −1 is overlapping with the characteristic CCTO absorption bands; therefore, Co (II)-O oscillations on their background are not reliably identified.…”

Section: Discussionmentioning

confidence: 92%

Spectroscopic study of Co-doped CaCu3Ti4O12

et al. 2021

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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 ~10 4 -10 5 ) in wide frequency ranges (10 2 -10 6 Hz) and temperature ranges (100 -600 K), showing neither ferroelectric nor relaxor properties. Due to the unique dielectric characteristics of calciumcopper 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 CaCu 3 Ti 4 O 12 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 CaCu 3 Ti 4 O 12 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.

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Section: Discussionmentioning

confidence: 92%

Spectroscopic study of Co-doped CaCu3Ti4O12

et al. 2021

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“…On the IR absorption spectra of the Na 0.89 Co 0.9 M 0.1 O 2 powders the absorption bands with extrema at 561-575 cm -1 were observed (Figure 1, lines 6-10), which correspond to the vibrations of (Co,M)-O bonds in the -[(Co,M)O 2 ]-layers of their crystal structure [25] as well as the absorption bands of Na 2 CoO 3 and Co 3 O 4 impurity phases, which are formed, as it was mentioned above, due to the partial degradation of the surface of the powders particles due to their interaction with atmospheric carbon dioxide. Values of absorption extrema of the samples studied were close each other; so, partial substitution of cobalt by other metals in Na 0.89 CoO 2 do not changed practically the energy of metal-oxygen interactions in its structure.…”

Section: Resultsmentioning

confidence: 99%

Effect of the Cobalt Substitution on the Structure and Properties of the Layered Sodium Cobaltate Derivatives

Klyndyuk¹,

Krasutskaya²,

Evseeva³

et al. 2015

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Using solid-state reactions method the ceramic samples of Na 0.89 Co 0.9 M 0.1 O 2 (M = Sc, Ti, Cr-Zn, Mo, W, Pb, Bi) solid solutions had been prepared, their lattice constants had been determined and their microstructure, thermal expansion, thermal conductivity, electrical conductivity and thermo-EMF had been measured, and their power factor and figure-of-merit values had been calculated. Effect of the cobalt substitution by other metals in the Na 0.89 CoO 2 on the crystal structure and physicochemical and functional properties of its derivatives was analyzed. It was found that Na 0.89 Co 0.9 M 0.1 O 2 cobaltates are the p-type conductors, which linear thermal expansion coefficient (LTEC) values varied within (1.24-2.05)•10-5 K-1. It was found that the best thermoelectric properties among the oxides studied possessed Na 0.89 Co 0.9 Ni 0.1 O 2 and Na 0.89 Co 0.9 Bi 0.1 O 2 solid solutions which power factor and figure-of-merit estimated values at 1100 K are equal to 0.919 and 0.660 mW/(m•K) and 1.12 and 0.83 respectively.

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“…In addition to studies with varying Na stoichiometry, there have been studies (Premila et al 2006) on CoO 2 layer doping. Substitution of transition metals like Ni, Mn and Ir in place of cobalt induces a metal-to-insulator transition even for the smallest concentration.…”

Section: Introductionmentioning

confidence: 99%