Microstructure of BaTiO₃–Bi(Mg1/2Ti1/2)O₃–BiFeO₃Piezoelectric Ceramics

The dependence of the ferroelectric and piezoelectric properties of (1- x )(0.33BaTiO 3 –0.67BiFeO 3 )– x Bi(Mg 1/2 Ti 1/2 )O 3 ( x = 0, 0.05, 0.10, and 0.15) on Bi(Mg 1/2 Ti 1/2 )O 3 content x associated with microstructural changes is studied. From the behaviour of electric field-induced polarization and strain, polarization switching and depolarizing become easier as Bi(Mg 1/2 Ti 1/2 )O 3 content x increases. Remanent polarization and dielectric constant decrease, while polarization saturation field increases with increasing x . Microstructural observation reveals that Bi(Mg 1/2 Ti 1/2 )O 3 addition enhances the compositional fluctuation of BaTiO 3 /BiFeO 3 ratio, which probably creates a nanometre-sized domain region with slightly BaTiO 3 -rich composition. Since this nanometre-sized domain may cause relatively large responses of polarization and strain to the applied electric field, an appropriate amount of Bi(Mg 1/2 Ti 1/2 )O 3 enhances the electric field-induced strain, resulting in the largest piezoelectric response at x = 0.05. However, excessive Bi(Mg 1/2 Ti 1/2 )O 3 degrades polarization and strain characteristics, because a number of Ba(Fe 1- x Mg x /2 Ti x /2 ) 12 O 19 grains are created as a secondary phase and cause the segregation of excess bismuth oxide phases with low dielectric constant into the boundaries of the ferroelectric/piezoelectric grains.