Effect of internal friction on transformation twin dynamics in perovskite Sr_x Ba₁-_x Sn O₃ (x=0.6,0.8)

The dynamics of transformation twins in Sr_x Ba₁-_x Sn O₃ (x=0.6,0.8) perovskite has been studied by dynamical mechanical analysis in three-point bend geometry. This material undergoes phase transitions from orthorhombic to tetragonal and cubic structures on heating. The mechanical loss signatures of the transformation twins include relaxation and frequency-independent peaks in the orthorhombic, and tetragonal phases, with no observed energy dissipation in the cubic phase. The macroscopic shape, orientation, and relative displacements of twin walls have been calculated from bending and anisotropy energies. The mechanical loss angle and distribution of relaxation time are discussed in terms of bending modes of domain walls.