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Crystal Chemistry and Phase Equilibria of the CaO-½Ho2O3-CoOz System at 885 °C in Air



Winnie K. Wong-Ng, William J. Laws, Qingzhen Huang, Jie Hou, James A. Kaduk, Saul H. Lapidus, Lynn Ribaud


The phase diagram of the CaO-½Ho2O3-CoOz system was determined at 885 ºC in air. This diagram offers detailed compatibility relationships in the ternary oxide system that are essential for processing and for the understanding of thermoelectric properties. The system consists of two calcium cobaltate thermoelectric compounds. The 2D thermoelectric oxide, (Ca3-xHox)Co4O9-z (0 x 0.5), has a misfit layered structure, and the 1D Ca3Co2O6 consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a stoichiometric compound without the substitution of Ho on the Ca site. No solid solution of the distorted perovskite, (Ho1-xCax)CoO3-z was established at this temperature. In the CaO-Ho2O3 system, while a small solid solution region was identified for (Ho1-xCax)O(3-z)/2 (0
Powder Diffraction


Phase diagram of CaO-½Ho2O3-CoOz at 885 °C in Air, thermoelectric oxide (Ca3-xHox)Co4O9-z, phase compatibility relationships, structure for (Ho1-xCax)O(3-z)/2


Wong-Ng, W. , Laws, W. , Huang, Q. , Hou, J. , Kaduk, J. , , S. and Ribaud, L. (2020), Crystal Chemistry and Phase Equilibria of the CaO-½Ho2O3-CoOz System at 885 °C in Air, Powder Diffraction, [online], (Accessed June 23, 2024)


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Created July 1, 2020, Updated October 3, 2020