Structural and transport properties of doped bismuth titanates and niobates

Cobalt- or Zn-doped bismuth titanates and Mg+Cu-doped bismuth niobate were synthesized by the method of organic-inorganic precursors combustion. Distribution of dopants over the sites of the pyrochlore structure was elucidated by X-ray powder diffraction structure refinement and pycnometric density...

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Bibliographic Details
Published in:Solid state ionics 2018-02, Vol.315, p.33-39
Main Authors: Sadykov, V.A., Koroleva, M.S., Piir, I.V., Chezhina, N.V., Korolev, D.A., Skriabin, P.I., Krasnov, A.V., Sadovskaya, E.M., Eremeev, N.F., Nekipelov, S.V., Sivkov, V.N.
Format: Article
Language:English
Subjects:
Antiferromagnetism
Atomic properties
Bismuth titanate
Bismuth titanates/niobates
Cations
Chemical compounds
Cobalt
Conductivity
Copper
Dopants
Lattice sites
Lattice vibration
Magnesium
Magnetic permeability
Mobility
Niobates
Niobium
Oxygen
Oxygen isotopes
Oxygen mobility
Structure
Studies
Titanates
Titanium
X ray powder diffraction
Zinc
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Summary:Cobalt- or Zn-doped bismuth titanates and Mg+Cu-doped bismuth niobate were synthesized by the method of organic-inorganic precursors combustion. Distribution of dopants over the sites of the pyrochlore structure was elucidated by X-ray powder diffraction structure refinement and pycnometric density analysis. Zinc and cobalt cations are mainly located in Bi sites appearing also in Ti sites at their high content. Mg cations are located only in Nb sites, while Cu cations are equally distributed between Bi and Nb sites. Magnetic susceptibility data confirm Сo2+ state of cobalt atoms revealed by NEXAFS. Antiferromagnetic exchange appears when Сo atoms enter the titanium sites. Electronic conductivity of p-type dominates for Co-doped samples in the 160–750°C temperature range. The oxygen mobility and surface reactivity were studied by the oxygen isotope heteroexchange with C18O2 in isothermal and temperature-programmed modes. Mobility of the lattice oxygen can be described by a homogeneous model. The oxygen mobility and surface reactivity are comparable for doped bismuth titanates and niobates correlating with conductivity and being the highest for Co and Cu-doped samples with disordered distribution of dopants between lattice sites. A6630L A7280G A8120E A8170J B2130 B2520E •Bi1.6CoxTi2O7 pyrochlores stable up to melting T were obtained for the first time.•Cobalt-containing bismuth titanates show a mixed conductivity.•An increase in Co content results in increase of the electronic conductivity.•A high O mobility was shown by oxygen isotope heteroexchange with C18O2.
ISSN:0167-2738
1872-7689
DOI:10.1016/j.ssi.2017.12.008