Bismuth layer-structured ferroelectrics with a formula of Sr_1−x(K,Ce)_x/2(Na_0.5Bi_0.5)Bi₄Ti₅O₁₈ (KCSNBT-x, x = 0.0, 0.1, 0.2 and 0.3), were prepared by a conventional solid-state reaction method. The X-ray diffraction analysis suggested that the substitution led to the formation of a layered perovskite structure. Plate-like morphologies of the grains were clearly observed in all samples. The activation energy value of the ionic conductivity suggested that defects were related to oxygen vacancies. Excellent electrical properties (e.g., d₃₃ ∼ 21 pC N⁻¹, 2P_r ∼ 16.4 μC cm⁻² and T_c ∼ 567 °C) were simultaneously obtained in the ceramic where x = 0.3. Additionally, thermal annealing studies indicated that the piezoelectric constant (d₃₃) of the KCSNBT-0.1 ceramic remains almost unchanged (22 pC N⁻¹, only decreased by 4%) at temperatures below 400 °C, demonstrating that this ceramic is a promising candidate for high-temperature applications.