Phase transition of Ca_2-xSm_xMnO₄ (x < 0.5)

The phase transition of Ca_2-xSm_xMnO₄ (x < 0.5) was investigated by low and high temperature X-ray diffractometry and thermal analysis. Depending on the Sm content, the solid solutions were classified into the tetragonal (0 ≤ x ≤ 0.3) and orthorhombic (0.3 < x < 0.5) phases at room temperature. As the temperature decreases, a structural sequence of high temperature tetragonal-low temperature orthorhombic-low temperature tetragonal phases was found to occur for the solid solution at x = 0.3. For x = 0.2, a new type of orthorhombic phase with a distortion along the [100] direction of the tetragonal phase was found below 240 K. A phase diagram for this system is proposed.