Composition-driven phase boundary and electrical properties in (Ba0.94Ca0.06)(Ti1–xMx)O3 (M = Sn, Hf, Zr) lead-free ceramics

Abstract

In this study, we systematically investigated the composition dependence of the phase structure, microstructure, and electrical properties of (Ba_0.94Ca_0.06)(Ti_1–xM_x)O₃ (M = Sn, Hf, Zr) ceramics synthesised by the conventional solid-state reaction method. The phase boundary type strongly depends on the composition, and then different electrical properties were exhibited. The addition of Hf and Zr can more quickly shift phase transition temperatures (T_R–O and T_O–T) to a higher temperature with respect to Sn, leading to the formation of different phase boundaries. In addition, different phase boundaries can also be affected by their doped contents. The R–O and O–T phase boundaries can be shown in the Sn-doped ceramics with x = 0.10, and the R–O phase boundary can exist in the Hf (x = 0.07) or Zr (x = 0.075)-doped ceramics. A high piezoelectric property of d₃₃ = 600 pC N⁻¹ can be achieved in the Sn-doped ceramics due to the involvement of converging R–O/O–T phase boundaries, an enhanced ferroelectric performance with P_r = 14.54 μC cm⁻² and E_c = 1.82 kV cm⁻¹ can be attained in the Zr-doped ceramics, and Hf would benefit from obtaining a large strain behaviour (∼0.20%). We believe that the electrical properties and the related physical mechanisms of BaTiO₃-based ceramics can be well unveiled by studying their chemical modification behavior.