Domain structure in (La, Pr)GaO₃ solid solutions

Abstract

Substitution of La by Pr in La_1−xPr_xGaO₃ solid solutions crystals leads to a decrease of spontaneous strains. There exist six possible twin states of the m3mFmmm species in the orthorhombic phase. The distorted perovskite unit cell becomes pseudotetragonal at composition x=0.51 what leads to degeneracy to three twin states (the m3mF4/mmm species). The 110 and 112 reflection twins and axial twins with compositional planes close to 211 (S-walls) were identified in crystals with x=0.05, 0.10, 0.30. All observed twins are characteristic for crystals of GdFeO₃ type perovskite-like structure. It was shown that orientations of S-walls do not depend on La/Pr ratio in the ranges of x ≤ 0.3 and strongly vary in the composition range 0.3 < x < 0.8. A tilt angle between two twin states across twin boundary in La_1−xPr_xGaO₃ is smaller than either in pure LaGaO₃ or PrGaO₃.

Key Words:

• twin
• solution
• (LaPr)GaO₃
• perovskite