Phase and structural behavior of SmAlO3–RAlO3 (R = Eu, Gd) systems

• Continuous solid solutions exist in the SmAlO3–RAlO3 (R = Eu, Gd) systems.
• Lattice parameter crossover was found in solid solutions Sm1 − xRxAlO3 (R = Eu, Gd).
• Thermally induced lattice crossovers occur in Sm0.9R0.1AlO3 at elevated temperatures.
• First-order structural phase transition Pbnm↔R3¯c was found in Sm1 − xRxAlO3 (R = Eu, Gd).
• Phase diagram of the systems SmAlO3–EuAlO3 and SmAlO3–GdAlO3 has been constructed.

Phase and structural behavior in the SmAlO3–RAlO3 (R = Eu, Gd) systems has been studied in a whole concentration range by means of laboratory X-ray diffraction, in situ synchrotron powder diffraction and differential thermal analysis techniques. Continuous solid solutions with orthorhombic perovskite structure have been found in both systems. Peculiarity of the solid solutions of Sm1 − xEuxAlO3 and Sm1 − xGdxAlO3 is the existence of two lattice parameter crossovers in each system occurred at xEu = 0.07 and 0.62 and at xGd = 0.04 and 0.33, respectively. The temperature induced lattice crossovers in the Sm0.9Eu0.1AlO3 and Sm0.9Gd0.1AlO3 samples have been found at 387 and 922 K and at 501 and 894 K. First-order reversible structural phase transformations Pbnm↔R3¯c have been detected in both systems at the elevated temperatures. The temperatures of these transitions increase linearly with the decreasing of the samarium content. Phase diagrams of the pseudo-binary systems SmAlO3–EuAlO3 and SmAlO3–GdAlO3 have been constructed.

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