Investigation of structural states and oxidation processes in Li 0.5Fe2.5O4-δ using TG analysis

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Abstract

Using the methods of X-ray phase and DSC analyses, a correlation is established between ordering/disordering of the structure of lithium pentaferrite (LPF - Li0.5Fe2.5O4-δ) and its nonstoichiometry with respect to oxygen. Ferrite specimens with a reduced content of oxygen were prepared by thermal annealing in vacuum (P = 2 × 10-4 mmHg). It is shown that this treatment results in oxygen nonstoichiometry and causes a transition of LPF into a state with random distribution of cations in the crystal lattice. Using nonisothermal thermogravimetry (TG), the kinetic dependences of oxygen absorption by the anion-deficient LPF are investigated within the temperature interval T = (350-640) C in the course of its oxidation annealing in air. The kinetic experiment data are processed with the Netzsch Thermokinetics software. The oxidation rate constants, the effective coefficients, and the activation energy of oxygen diffusion in the material under study are derived. Their values are in a satisfactory agreement with those earlier obtained for the lithium-titanium ferrite ceramic material of the following composition: Li0.649Fe 1.598Ti0.5Zn0.2Mn0.051O 4-δ. The effective activation energy of oxygen diffusion in LPF calculated within the temperature interval T = (350-640) C is found to be Ed = 1.88 eV. In its value, it is close to the activation energy of oxygen diffusion along grain-boundaries in the lithium-titanium ferrite ceramic material.

Original languageEnglish
Pages (from-to)1207-1212
Number of pages6
JournalJournal of Thermal Analysis and Calorimetry
Volume108
Issue number3
DOIs
Publication statusPublished - Jun 2012

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thermogravimetry
Thermogravimetric analysis
Oxygen
Oxidation
oxidation
oxygen
Lithium
Ferrite
ferrites
Activation energy
lithium
Ceramic materials
activation energy
Titanium
titanium
Annealing
ceramics
intervals
Kinetics
annealing

Keywords

  • Activation energy
  • Diffusion
  • Lithium pentaferrite
  • Oxygen nonstoichiometry

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Condensed Matter Physics

Cite this

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title = "Investigation of structural states and oxidation processes in Li 0.5Fe2.5O4-δ using TG analysis",
abstract = "Using the methods of X-ray phase and DSC analyses, a correlation is established between ordering/disordering of the structure of lithium pentaferrite (LPF - Li0.5Fe2.5O4-δ) and its nonstoichiometry with respect to oxygen. Ferrite specimens with a reduced content of oxygen were prepared by thermal annealing in vacuum (P = 2 × 10-4 mmHg). It is shown that this treatment results in oxygen nonstoichiometry and causes a transition of LPF into a state with random distribution of cations in the crystal lattice. Using nonisothermal thermogravimetry (TG), the kinetic dependences of oxygen absorption by the anion-deficient LPF are investigated within the temperature interval T = (350-640) C in the course of its oxidation annealing in air. The kinetic experiment data are processed with the Netzsch Thermokinetics software. The oxidation rate constants, the effective coefficients, and the activation energy of oxygen diffusion in the material under study are derived. Their values are in a satisfactory agreement with those earlier obtained for the lithium-titanium ferrite ceramic material of the following composition: Li0.649Fe 1.598Ti0.5Zn0.2Mn0.051O 4-δ. The effective activation energy of oxygen diffusion in LPF calculated within the temperature interval T = (350-640) C is found to be Ed = 1.88 eV. In its value, it is close to the activation energy of oxygen diffusion along grain-boundaries in the lithium-titanium ferrite ceramic material.",
keywords = "Activation energy, Diffusion, Lithium pentaferrite, Oxygen nonstoichiometry",
author = "Surzhikov, {Anatoly Petrovich} and Frangulyan, {T. S.} and Ghyngazov, {S. A.} and Lysenko, {E. N.}",
year = "2012",
month = "6",
doi = "10.1007/s10973-011-1734-z",
language = "English",
volume = "108",
pages = "1207--1212",
journal = "Journal of Thermal Analysis and Calorimetry",
issn = "1388-6150",
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TY - JOUR

T1 - Investigation of structural states and oxidation processes in Li 0.5Fe2.5O4-δ using TG analysis

AU - Surzhikov, Anatoly Petrovich

AU - Frangulyan, T. S.

AU - Ghyngazov, S. A.

AU - Lysenko, E. N.

PY - 2012/6

Y1 - 2012/6

N2 - Using the methods of X-ray phase and DSC analyses, a correlation is established between ordering/disordering of the structure of lithium pentaferrite (LPF - Li0.5Fe2.5O4-δ) and its nonstoichiometry with respect to oxygen. Ferrite specimens with a reduced content of oxygen were prepared by thermal annealing in vacuum (P = 2 × 10-4 mmHg). It is shown that this treatment results in oxygen nonstoichiometry and causes a transition of LPF into a state with random distribution of cations in the crystal lattice. Using nonisothermal thermogravimetry (TG), the kinetic dependences of oxygen absorption by the anion-deficient LPF are investigated within the temperature interval T = (350-640) C in the course of its oxidation annealing in air. The kinetic experiment data are processed with the Netzsch Thermokinetics software. The oxidation rate constants, the effective coefficients, and the activation energy of oxygen diffusion in the material under study are derived. Their values are in a satisfactory agreement with those earlier obtained for the lithium-titanium ferrite ceramic material of the following composition: Li0.649Fe 1.598Ti0.5Zn0.2Mn0.051O 4-δ. The effective activation energy of oxygen diffusion in LPF calculated within the temperature interval T = (350-640) C is found to be Ed = 1.88 eV. In its value, it is close to the activation energy of oxygen diffusion along grain-boundaries in the lithium-titanium ferrite ceramic material.

AB - Using the methods of X-ray phase and DSC analyses, a correlation is established between ordering/disordering of the structure of lithium pentaferrite (LPF - Li0.5Fe2.5O4-δ) and its nonstoichiometry with respect to oxygen. Ferrite specimens with a reduced content of oxygen were prepared by thermal annealing in vacuum (P = 2 × 10-4 mmHg). It is shown that this treatment results in oxygen nonstoichiometry and causes a transition of LPF into a state with random distribution of cations in the crystal lattice. Using nonisothermal thermogravimetry (TG), the kinetic dependences of oxygen absorption by the anion-deficient LPF are investigated within the temperature interval T = (350-640) C in the course of its oxidation annealing in air. The kinetic experiment data are processed with the Netzsch Thermokinetics software. The oxidation rate constants, the effective coefficients, and the activation energy of oxygen diffusion in the material under study are derived. Their values are in a satisfactory agreement with those earlier obtained for the lithium-titanium ferrite ceramic material of the following composition: Li0.649Fe 1.598Ti0.5Zn0.2Mn0.051O 4-δ. The effective activation energy of oxygen diffusion in LPF calculated within the temperature interval T = (350-640) C is found to be Ed = 1.88 eV. In its value, it is close to the activation energy of oxygen diffusion along grain-boundaries in the lithium-titanium ferrite ceramic material.

KW - Activation energy

KW - Diffusion

KW - Lithium pentaferrite

KW - Oxygen nonstoichiometry

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U2 - 10.1007/s10973-011-1734-z

DO - 10.1007/s10973-011-1734-z

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VL - 108

SP - 1207

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JO - Journal of Thermal Analysis and Calorimetry

JF - Journal of Thermal Analysis and Calorimetry

SN - 1388-6150

IS - 3

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