Thermodynamic studies on SrFe{sub 12}O{sub 19}(s), SrFe{sub 2}O{sub 4}(s), Sr{sub 2}Fe{sub 2}O{sub 5}(s) and Sr{sub 3}Fe{sub 2}O{sub 6}(s)

Journal Article · Thu Feb 15 00:00:00 EST 2007 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2006.11.012· OSTI ID:21015679

Parida, S C ^[1]; Dash, S ^[1]; Singh, Z ^[1]; Sen, B K ^[1]; Venugopal, V ^[1]

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1. Product Development Section, RC and I Group, Bhabha Atomic Research Centre, Trombay, Mumbai-400085 (India)

The citrate-nitrate gel combustion route was used to prepare SrFe{sub 2}O{sub 4}(s), Sr{sub 2}Fe{sub 2}O{sub 5}(s) and Sr{sub 3}Fe{sub 2}O{sub 6}(s) powders and the compounds were characterized by X-ray diffraction analysis. Different solid-state electrochemical cells were used for the measurement of emf as a function of temperature from 970 to 1151K. The standard molar Gibbs energies of formation of these ternary oxides were calculated as a function of temperature from the emf data and are represented as {delta}{sub f}G{sub m}{sup o} (SrFe{sub 2}O{sub 4}, s, T)/kJmol{sup -1} (+/-1.7)=-1494.8+0.3754(T/K) (970=<T/K=<1151). {delta}{sub f}G{sub m}{sup o} (Sr{sub 2}Fe{sub 2}O{sub 5}, s, T)/kJmol{sup -1} (+/-3.0)=-2119.3+0.4461(T/K) (970=<T/K=<1149). {delta}{sub f}G{sub m}{sup o} (Sr{sub 3}Fe{sub 2}O{sub 6}, s, T)/kJmol{sup -1} (+/-7.3)=-2719.8+0.4974(T/K) (969=<T/K=<1150). Standard molar heat capacities of these ternary oxides were determined from 310 to 820K using a heat flux type differential scanning calorimeter (DSC). Based on second law analysis and using the thermodynamic database FactSage software, thermodynamic functions such as {delta}{sub f}H{sup o}(298.15K), S{sup o}(298.15K) S{sup o}(T), C{sub p}{sup o}(T), H{sup o}(T), {l_brace}H{sup o}(T)-H{sup o}(298.15K){r_brace}, G{sup o}(T), free energy function (fef), {delta}{sub f}H{sup o}(T) and {delta}{sub f}G{sup o}(T) for these ternary oxides were also calculated from 298 to 1000K.

• OSTI ID: 21015679
• Journal Information: Journal of Solid State Chemistry, Vol. 180, Issue 2; Other Information: DOI: 10.1016/j.jssc.2006.11.012; PII: S0022-4596(06)00597-4; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CALORIMETERS
CALORIMETRY
CITRATES
COMBUSTION
COMPUTER CODES
CURIE POINT
ELECTROCHEMICAL CELLS
ELECTROMOTIVE FORCE
FERRITES
FREE ENERGY
GELS
HEAT FLUX
NITRATES
SPECIFIC HEAT
STRONTIUM COMPOUNDS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
X-RAY DIFFRACTION