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Title: Oxygen content and structures of La{sub 1-x}Ca{sub x}MnO{sub 3+d} as a function of synthesis conditions

Abstract

Using thermogravimetric analysis measurements, oxygen content was measured for La{sub 1{minus}x}Ca{sub x}MnO{sub 3+d} (0 {le} x {le} 0.38) samples prepared at high oxygen pressure. The oxygen content was found to decrease uniformly with increasing x for samples annealed at 12 and 140 atm O{sub 2} at 800 C, slowly cooled in 1, 20, and 100% O{sub 2}, as well as for samples in thermal equilibrium at high temperatures of {approximately}1000--1400 C. Annealing at a specific temperature and oxygen pressure leads to approximately constant hole doping over an extended range of Ca substitution x. The most favorable synthesis conditions for obtaining stoichiometric, d = 0, samples were determined. The data suggest that several studies reported in the literature were done on significantly nonstoichiometric materials. Structural results show that, in addition to the orthorhombic Pbnm O{prime} (cla < {radical}2) and O* (a {approximately} b {approximately} c/{radical}2) structures, the rhombohedral R{bar 3}c structure is stabilized at high oxygen contents for x {le} 0.14. A sequence of observed structures and a decrease of the unit cell volume with increasing d confirm that the additional holes are doped uniformly by cation-vacancy defects for all studied x.

Authors:
; ;  [1];  [2];  [3]
  1. Northern Illinois Univ., DeKalb, IL (United States). Dept. of Physics
  2. Northern Illinois Univ., DeKalb, IL (United States). Dept. of Physics|[Polish Academy of Sciences, Wroclaw (Poland). Inst. of Low Temperature and Structure Research
  3. Argonne National Lab., IL (United States). Materials Science Div.
Publication Date:
Research Org.:
Argonne National Laboratory (ANL), Argonne, IL
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
696679
DOE Contract Number:  
W-31109-ENG-38
Resource Type:
Journal Article
Journal Name:
Journal of Solid State Chemistry
Additional Journal Information:
Journal Volume: 146; Journal Issue: 2; Other Information: PBD: Sep 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CRYSTAL STRUCTURE; SYNTHESIS; LANTHANUM OXIDES; CALCIUM OXIDES; MANGANESE OXIDES; STOICHIOMETRY; TEMPERATURE DEPENDENCE; THERMAL GRAVIMETRIC ANALYSIS; X-RAY DIFFRACTION; EXPERIMENTAL DATA

Citation Formats

Dabrowski, B., Dybzinski, R., Chmaissem, O., Bukowski, Z., and Jorgensen, J.D. Oxygen content and structures of La{sub 1-x}Ca{sub x}MnO{sub 3+d} as a function of synthesis conditions. United States: N. p., 1999. Web. doi:10.1006/jssc.1999.8389.
Dabrowski, B., Dybzinski, R., Chmaissem, O., Bukowski, Z., & Jorgensen, J.D. Oxygen content and structures of La{sub 1-x}Ca{sub x}MnO{sub 3+d} as a function of synthesis conditions. United States. doi:10.1006/jssc.1999.8389.
Dabrowski, B., Dybzinski, R., Chmaissem, O., Bukowski, Z., and Jorgensen, J.D. Wed . "Oxygen content and structures of La{sub 1-x}Ca{sub x}MnO{sub 3+d} as a function of synthesis conditions". United States. doi:10.1006/jssc.1999.8389.
@article{osti_696679,
title = {Oxygen content and structures of La{sub 1-x}Ca{sub x}MnO{sub 3+d} as a function of synthesis conditions},
author = {Dabrowski, B. and Dybzinski, R. and Chmaissem, O. and Bukowski, Z. and Jorgensen, J.D.},
abstractNote = {Using thermogravimetric analysis measurements, oxygen content was measured for La{sub 1{minus}x}Ca{sub x}MnO{sub 3+d} (0 {le} x {le} 0.38) samples prepared at high oxygen pressure. The oxygen content was found to decrease uniformly with increasing x for samples annealed at 12 and 140 atm O{sub 2} at 800 C, slowly cooled in 1, 20, and 100% O{sub 2}, as well as for samples in thermal equilibrium at high temperatures of {approximately}1000--1400 C. Annealing at a specific temperature and oxygen pressure leads to approximately constant hole doping over an extended range of Ca substitution x. The most favorable synthesis conditions for obtaining stoichiometric, d = 0, samples were determined. The data suggest that several studies reported in the literature were done on significantly nonstoichiometric materials. Structural results show that, in addition to the orthorhombic Pbnm O{prime} (cla < {radical}2) and O* (a {approximately} b {approximately} c/{radical}2) structures, the rhombohedral R{bar 3}c structure is stabilized at high oxygen contents for x {le} 0.14. A sequence of observed structures and a decrease of the unit cell volume with increasing d confirm that the additional holes are doped uniformly by cation-vacancy defects for all studied x.},
doi = {10.1006/jssc.1999.8389},
journal = {Journal of Solid State Chemistry},
number = 2,
volume = 146,
place = {United States},
year = {1999},
month = {9}
}