Vaporization of LaCrO{sub 3}: Partial and integral thermodynamic properties

Journal Article · Sun Dec 01 04:00:00 EST 1996 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1996.tb08104.x· OSTI ID:422735

Peck, D H; Miller, M; Kobertz, D; Nickel, H; Hilpert, K ^[1]

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1. Research Centre Juelich (Germany). Inst. for Materials in Energy Systems

The vaporization of LaCrO{sub 3}(s) and samples of the composition LaCrO{sub 3} + La{sub 2}O{sub 3} was investigated in the temperature range of 1,887--2,333 K by Knudsen effusion mass spectrometry using Knudsen cells made of tungsten lined completely with iridium. The species Cr(g), CrO(g), CrO{sub 2}(g), and LaO(g) were identified in the vapor. Their partial pressures were determined by calibration with pure platinum solid. The thermodynamic activity of Cr{sub 2}O{sub 3}, a{sub Cr{sub 2}O{sub 3}}, in LaCrO{sub 3} for the Cr{sub 2}O{sub 3}-poor phase boundary of this phase was ln a{sub Cr{sub 2}O{sub 3}} = {minus}(17953/T) {minus} 0.485 (temperature T given in K) for the temperature range of the measurements with a probable overall error of {+-}13%. The following values and temperature dependence of {Delta}G{sub f,T}{sup o} resulted for the formation of LaCrO{sub 3}(s) according to the reaction 0.5Cr{sub 2}O{sub 3}(s) + 0.5La{sub 2}O{sub 3}(s) {r_arrow} LaCrO{sub 3}(s): {Delta}G{sub f,2100}{sup o} = {minus}78.9 {+-} 1.1 kJ/mol, {Delta}H{sub f,298}{sup o} = {minus}76.8 {+-} 5.2 kJ/mol, and {Delta}G{sub f,T}{sup o}(kJ/mol) = {minus}74.7 {minus} 0.00202T. Computations for the vaporization of LaCrO{sub 3} were conducted to show the volatility of this material in different atmospheres at high temperatures.

• Sponsoring Organization: USDOE
• OSTI ID: 422735
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 12 Vol. 79; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALIBRATION
CHROMIUM OXIDES
EVAPORATION
EXPERIMENTAL DATA
FORMATION FREE ENERGY
IRIDIUM
KNUDSEN FLOW
LANTHANUM OXIDES
MASS SPECTROSCOPY
PARTIAL PRESSURE
PLATINUM
TEMPERATURE RANGE 1000-4000 K
THERMODYNAMIC PROPERTIES
TUNGSTEN
X-RAY DIFFRACTION