Phase and Structural Behaviour of the $PrAlO_{3}-SmAlO_{3}$ System

High resolution in situ X-ray powder diffraction applying synchrotron radiation and differential thermal analysis/scanning calorimetry methods have been used to examine the pseudo-binary system $PrAlO_3-SmAlO_3$. Two kinds of solid solutions with rhombohedral and orthorhombic structure exist at room temperature. At elevated temperatures, a continuous phase transition Pm3m ↔ R3c and a first-order transformation R3c ↔ Pbmn occur in the two respective phases. A sequence of low-temperature phase transformations R3c ↔ Imma ↔ C2/m has been detected in $Pr_{1-x}Sm_xAlO_3$ samples with x < 0.35. Based on in situ powder diffraction and differential thermal analysis/scanning calorimetry data, the phase diagram of the pseudo-binary system $PrAlO_3-SmAlO_3$ has been constructed