Thermodynamics of Co3O4: a possible electron spin unpairing transition in Co3+

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The free energy of the reaction: {Mathematical expression} has been studied between 890 and 1,240 K using an e.m.f. technique. There is a phase transition in Co3O4 at 1,120±20 K which is accompanied by a large change in entropy (∼47 JK-1 mol-1 of Co3O4), and a rapid increase in unit cell volume and in electical conductivity. This is interpreted to be due to a partial change in electronic spin states in Co3 + from the spin-paired (low spin) configuration observed at room temperature to the spin-unpaired (high spin) state. The transition is probably not first order.

Original languageEnglish
Pages (from-to)149-154
Number of pages6
JournalPhysics and Chemistry of Minerals
Issue number3
Publication statusPublished - Jul 1985
Externally publishedYes

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