Field-induced ergodic relaxor to ferroelectric transition in (1-2x) Bi0.5Na0.5TiO3-xBaTiO3-xLaFeO3 ternary system and associated electro-mechanical properties

Solid solutions of Bi0.5Na0.5TiO3 (BNT) with other perovskites provide greater promise for lead-free piezoelectric and /electrostrictive application. Herein, the authors synthesized a series of BNT based ternary solid solution (1-2x) Bi0.5Na0.5TiO3-xBaTiO3-xLaFeO3: BNT-BT-LFO [x = 0.01, 0.03, 0.05, 0.07, and 0.09] through a standard solid-state reaction route. Rietveld analysis of the powder diffraction data reveals composition-driven single and dual-phase combinations in the solid solution. The compositions corresponding to x = 0.01 and 0.03 are found to be crystallized in the ferroelectric rhombohedral (Rc3) system, while the compositions with x = 0.05, 0.07, and 0.09 are found to have co-existence of rhombohedral (Rc3) and pseudo-cubic (pm-3m) phases. Especially, BNTBT-LFO (x = 0.05) has a dominant pseudo cubic (pm-3m) phase which flips to a dominant rhombohedral phase for x = 0.07 and 0.09. BNT-BT-LFO (x = 0.05) also shows a clear frequency dependent diffused phase transition, characteristics of relaxor ferroelectric. Subsequently, a large strain of 0.36 %, Smax/Emax of 608 pm/V and an electrostrictive co-efficient (Q33) of 0.036 m4 C2 is measured for this composition attributed to the field-induced ergodic relaxor to ferroelectric phase transition.