The thermodynamic properties of yttrium and dysprosium manganites

The standard Gibbs free energy of formation of calcium chromium (III) oxide in the temperature range (1073 to 1273)K

“…These discrepancies may be due to an inaccuracy of the tolerance factor assigned to the enthalpy and entropy calculations. However, a quite reasonable agreement of the values determined previously [5], as well as given in [2], is obtained.…”

“…The left half-cell (1) was made from a mixture of CaO and CaF 2 powders with a molar ratio 5:1. The left half-cells (2) and (3), and the right half-cell (3) were obtained by mixing Ni or Cr powder with their respective oxide in a molar ratio 1:1 and pressing the mixture into pellets 3 mm thick and 12 mm in diameter. The material for the preparation of the right half-cell (1) 3 , mixed in a molar ratio CaO: Cr 2 O 3 = 1:5, to an excess amount of (oxalic acid + ethanol) solution.…”

“…The CaF 2 powder involved in both half-cells (1) played an essential role in establishing the chemical potential of oxygen. However, cells (2) and (3) were reversible with respect to oxygen ions. A single crystal CaF 2 electrolyte was used extensively for thermodynamic characterisation of many oxide systems [6].…”

“…Kovba and Skolis determined the Gibbs free energy, the enthalpy and the entropy of formation of CaCr 2 O 4 in the temperature range (1250 to 1550) K by e.m.f. measurements of galvanic cells involving calcium fluoride and calcia doped thoria electrolytes [2]. They also calculated the Gibbs free energy of formation of CaCr 2 O 4 taking for the calculation the equilibrium constant for the reaction of reduction of CaCr 2 O 4 with CO, determined earlier by Havlica and Panek for the temperatures of 1663 K and 1933 K [3].…”