Phase and structural behaviour of the PrAlO3–LaAlO3 pseudo-binary system

High-resolution in situ X-ray powder diffraction applying synchrotron radiation has been used to examine the occurring crystal structures and the thermal behaviour of the solid solution Pr1−xLaxAlO3 in a wide temperature range 12–1173 K. At room temperature all studied samples in the whole composition range of the pseudo-binary system PrAlO3–LaAlO3 adopt a rhombohedral perovskite structure. The phases Pr1−xLaxAlO3 with x=0.56 and 0.66 undergo a sequence of three phase transitions I2/m↔Imma↔R3¯c↔Pm3¯m. For the sample with x=0.24 a series of four (I4/mcm↔I2/m↔Imma↔R3¯c↔Pm3¯m) phase transitions has been observed and for x=0.86 two transformations were apparent (I2/m↔R3¯c↔Pm3¯m). Crystal structure parameters for all studied compositions Pr1−xLaxAlO3 have been determined. Based on in situ powder diffraction and DTA/DSC data, the phase diagram of the pseudo-binary system PrAlO3–LaAlO3 has been constructed.