Phase evolution, dielectric, ferroelectric, and piezoelectric properties of Bi(Mg0.5Hf0.5)O3–modified BiFeO3–BaTiO3

Abstract

Bi(Mg0.5Hf0.5)O3–modified BiFeO3–BaTiO3 ternary solid solutions of (0.725-x)BiFeO3-0.275BaTiO3-xBi(Mg0.5Hf0.5)O3 (0 <x ≤ 0.05, abbreviated as BFO-BTO-xBMHO) were prepared for lead-free piezoelectrics. The addition of BMHO delivers a rhombohedral (R3c, denoted as R-phase) to tetragonal (P4mm, denoted as T-phase) phase transition at x = 0.05, giving the coexistence of R- and T-phase in intermediate compositions: R-phase dominated in x = 0.01–0.02 and T-phase dominated in x = 0.03–0.04. The increment of BMHO tunes the grain size, lowers the ferroelectric transition temperature (TC) and dielectric loss (tanδ), and drives a gradually ferroelectric to relaxor transition. The morphotropic phase boundary between the R-and T-phases, together with the homogeneous morphology, results in the best performance for x = 0.04 case with piezoelectric d33 of 130 pC/N, Kp of 0.286, Qm of 58.993, electrostrain Smax of 0.18%, and TC of 428 °C, showing potential applications for lead-free piezoelectric ceramics at considerably high temperature.