TY - JOUR
T1 - La2CuO4 + δ
T2 - Synthesis Under High Oxygen Pressure and Study of Phase Relations and Energetics
AU - Rapp, R. P.
AU - Mehta, A.
AU - DiCarlo, J.
AU - Navrotsky, A.
N1 - Funding Information:
This research was supported under Department of Energy Grant No. DEFGO289ER45394 (AN); E. Bruce Watson of Rensselaer Polytechnic Institute is thanked for the use of his high-pressure experimental facilities for several of these experiments.
PY - 1994/10
Y1 - 1994/10
N2 - 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).
AB - 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).
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U2 - 10.1557/JMR.1994.0008
DO - 10.1557/JMR.1994.0008
M3 - Article
AN - SCOPUS:0028201567
SN - 0884-2914
VL - 9
SP - 8
EP - 12
JO - Journal of Materials Research
JF - Journal of Materials Research
IS - 1
ER -