Composition and electric field driven studies on modified NBT-based lead-free ceramics

A considerable increase in the c/a ratio, tilt angle, octahedral strain, and Ti-Ti distance with an application of electric field was observed for all the compositions in (1-x) (Na_0.5Bi_0.5TiO₃).x(Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃) ceramics. In the x = 0.09 sample, a P4bm phase (∼45 %) was observed which reduced to ∼ 15 % upon poling. The tilt angle modifies the A₁ phonon mode at 784 cm⁻¹ upon substitution and application of the electric field. Incorporating Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ increased the maximum dielectric permittivity (ε_m) from ∼ 2466 (x = 0) to ∼ 3231 (x = 0.09). The degree of diffuseness (γ) also increased with substitution from ∼ 1.384 (x = 0) to ∼ 1.980 (x = 0.09). With poling the value of γ was observed to decrease for each composition. The transformation from a compressive octahedral strain to a tensile one increased the piezoelectric coefficient (d₃₃). The d₃₃ value increased from ∼ 70 (x = 0) to ∼ 120 (x = 0.06).