The effect of point defects on ferroelastic phase transition of lanthanum-doped calcium titanate ceramics

In the present paper, La-doped CaTiO₃ is studied to investigate the effect of point defects on ferroelastic phase transition of the ceramics. The dynamic mechanical measurements show that the transition temperature of the orthorhombic to tetragonal phase transition of Ca_(1-x)La _2x/3TiO₃ decreases with increasing dopant (La) concentration x. The samples with the dopant content of x = 0.45 and 0.7 exhibit different structure evolution features during their transition processes as revealed by in situ powder X-ray diffraction (XRD) measurement. Moreover, when x = 0.7, the storage modulus shows a frequency-dependent minimum at T _g, which can be well fitted with the Vogel-Fulcher relation, and the corresponding internal friction also exhibits a frequency-dependent peak within the same temperature regime. These results thus indicate that doping La suppresses ferroelastic phase transition in CaTiO₃ and induces a "glassy-like" behavior in Ca_(1-x)La_2x/3TiO ₃, which is similar to "strain glass" in Ni-doped Ti _50-xNi_50+x.