1. (a) XRD patterns, (b) Raman spectra, and (c-e) Raman shifts of each mode as a function of x for BCTWTaS-100x ceramics

S1. Complex impedance spectra of BCTWTaS-100x ceramics at different temperatures

2. (a-e) SEM images of the polished thermally-etched surfaces of BCTWTaS-100x ceramics and (f) corresponding density

S2. (a-e) M''/M''_max as a function of frequency of BCTWTaS-100x ceramics at different temperatures; (g) Temperature dependence of DC resistivity of BCTWTaS-100x ceramics; (h) Arrhenius relationship between DC resistivity and temperature of BCTWTaS-100x ceramics in the range of 200-600 ℃; (i) Activation energy calculated by fitting the experimental data from low-temperature region and high-temperature region

3. High-resolution XPS spectra of (a, b) O, Bi for BCTWTaS-100x ceramics and (c) Ce for BCTWTaS-3 ceramic

S3. 9(a) Schematic diagram of nanoindentation and (b-f) load-depth curves for the BCTWTaS-x ceramics

4. (a, c) Amplitude and (b, d) phase images of vertical PFM for (a, b) BCTWTaS-0 and (c, d) BCTWTaS-3 ceramics with a scanning region of 4 μm×4 μm

5. (a-e) P-E hysteresis loops and I-E curves of BCTWTaS-100x ceramics, and (f) composition dependence of P_r and E_c

6. (a) Composition dependence of d₃₃ and (b-d) temperature dependence of (b) d₃₃, (c) ε_r and (d) tanδ (100 kHz) for BCTWTaS-100x ceramics