La2CuO4 + δ: Synthesis Under High Oxygen Pressure and Study of Phase Relations and Energetics

R. P. Rapp, A. Mehta, J. DiCarlo, A. Navrotsky

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

High oxygen pressures have been achieved in a piston-cylinder apparatus using a double capsule assembly consisting of a sealed outer Au capsule, containing an oxygen source (KMnO4), and an inner, open Pt capsule containing the sample. Using this technique, La2Cu04 was annealed at 800 °C, 5-25 kbar for 2-4 h. Transposed temperature drop calorimetry at 704 °C was used to determine the enthalpy of oxidation, and weight loss measurements characterized the oxygen nonstoichiometry, δ, in La2CuO4 + δin the high-pressure, oxygen-annealed samples. For samples analyzed at room temperature, x-ray diffraction measurements show that beyond δ ≈ 0.10-0.13, additional oxygen is accommodated in a perovskite-like LaCuO3-αphase. An analysis of the thermochemical measurements indicates that the nature of holes in La2CuO4+scould change in the range of δ ≈ 0.03-0.06.16,17It is further suggested that the observed change in the thermochemical behavior in the range of δ ≈ 0.03-0.06 could be the driving influence behind the spinodal decomposition of La2CuO4+δat low temperatures (Dabrowski et al.10).

Original languageEnglish (US)
Pages (from-to)8-12
Number of pages5
JournalJournal of Materials Research
Volume9
Issue number1
DOIs
StatePublished - Oct 1994
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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