Crystal Chemistry and Phase Equilibria of the CaO-½Dy2O3-CoOz System at 885 °C in Air
Winnie K. Wong-Ng, William J. Laws, James A. Kaduk
The CaO-½Dy2O3-CoOz system prepared at 885 °C in air consists of two calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca3-xDyx)Co4O9-z (0 x 0.6) which has a misfit layered structure, and the 1D Ca3Co2O6 which consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a stoichiometric compound without the substitution of Dy on the Ca site. No solid solution of the distorted perovskite, (Dy1-xCax)CoO3-z was established at this temperature (confirmed by X-ray Rietveld refinements). In the peripheral binary system of CaO-Dy2O3, while a small solid solution region was identified for (Dy1-xCax)O(3-z)/2 (0 x 0.075), Dy was not present in the Ca site of CaO. In addition, neither the reported Dy2CoO4 phase in the Dy2O -CoOz system nor the Ca- doped (Dy1+xCa1-x)CoO4-z phase was present at 885 °C. Three solid solution tie-line regions and four three-phase regions were determined in the CaO-½Dy2O3-CoOz system, which is substantially different from the other CaO-½R2O3-CoOz systems where R=La, Nd, Sm, Eu, and Gd. A comparison of the phase diagrams between the CaO-½Dy2O3-CoOz system and the CaO-½La2O3-CoOz system and the CaO-½Gd2O3-CoOz system is also presented in this paper.
, Laws, W.
and Kaduk, J.
Crystal Chemistry and Phase Equilibria of the CaO-½Dy2O3-CoOz System at 885 °C in Air, Solid State Sciences, [online], https://doi.org/10.1016/j.solidstatesciences.2018.
(Accessed May 28, 2023)