Thermochemical studies on SrFe{sub 12}O{sub 19}(s)

Journal Article · Mon Feb 14 23:00:00 EST 2005 · Materials Research Bulletin

DOI:https://doi.org/10.1016/j.materresbull.2004.10.015· OSTI ID:20889735

Rakshit, S K ^[1]; Parida, S C ^[1]; Dash, S ^[1]; Singh, Z ^[1]; Prasad, R ^[1]; Venugopal, V ^[1]

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1. Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

The citrate-nitrate gel combustion route was used to prepare SrFe{sub 12}O{sub 19}(s) powder sample and the compound was characterized by X-ray diffraction analysis. A solid-state electrochemical cell of the type: (-)Pt, O{sub 2}(g)/(CaO(s)+CaF{sub 2}(s))//CaF{sub 2}(s)//(SrFe{sub 12}O{sub 19}(s)+SrF{sub 2}(s)+Fe{sub 2}O{sub 3}(s))/O{sub 2}(g), Pt(+) was used for the measurement of emf as a function of temperature from 984 to 1151K. The standard molar Gibbs energy of formation of SrFe{sub 12}O{sub 19}(s) was calculated as a function of temperature from the emf data and is given by: {delta}{sub f}G{sub m}{sup o} (SrFe{sub 12}O{sub 19}, s, T)/kJmol{sup -1} (+/-1.3)=-5453.5+1.5267x(T/K). Standard molar heat capacity of SrFe{sub 12}O{sub 19}(s) was determined in two different temperature ranges 130-325K and 310-820K using a heat flux type differential scanning calorimeter (DSC). A heat capacity anomaly was observed at 732K, which has been attributed to the magnetic order-disorder transition from ferrimagnetic state to paramagnetic state. The standard molar enthalpy of formation, {delta}{sub f}H{sub m}{sup o} (298.15K) and the standard molar entropy, S{sub m}{sup o} (298.15K) of SrFe{sub 12}O{sub 19}(s) were calculated by second law method and the values are -5545.2kJmol{sup -1} and 633.1JK{sup -1}mol{sup -1}, respectively.

• OSTI ID: 20889735
• Journal Information: Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 2 Vol. 40; ISSN MRBUAC; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALCIUM FLUORIDES
CALORIMETERS
CALORIMETRY
CITRATES
COMBUSTION
ELECTROCHEMICAL CELLS
ELECTROCHEMISTRY
ELECTROMOTIVE FORCE
FERRITES
FORMATION HEAT
HEAT FLUX
IRON OXIDES
NITRATES
ORDER-DISORDER TRANSFORMATIONS
PARAMAGNETISM
SPECIFIC HEAT
STRONTIUM FLUORIDES
TEMPERATURE DEPENDENCE
X-RAY DIFFRACTION