Structural phase diagram of Ca1-xYxMnO: Characterization of phases

To help the understanding of the physical behavior of Ca1 - xYxMnO3, its ph ase diagram in the whole x concentration range was investigated taking into account the stability of phases and the possible coexistence of different structural phases. By careful analysis of powder X-ray diffraction (XRD) pa tterns, we were able to observe the following phase diagram: (i) Orthorhomb ic phases were detected both in the region of 0 less than or equal to x les s than or equal to 0.25 (O type phase with Ca site twelve fold coordinated) and in the region of 0.5 less than or equal to x < 0.75 (O' type phase wit h Ca site ninefold coordinated). (ii) Phase segregation for 0.25 <less than or equal to> x less than or equal to 0.5 and for x greater than or equal t o 0.75 that have not been reported previously, hexagonal YMnO3 segregates a s a separate phase for x > 0.75, and for 0.25 less than or equal to x less than or equal to 0.5 the coexistence of Ca0.75Y0.25MnO3 (O) and Ca0.5Y0.5Mn O3 (O') have to be included in the refinement for it to converge. (C) 2001 Academic Press.