From Fig. 3, it can be found that the dielectric constant decreases with increasing pressure, which is the same as Yang et al.11) and Zhu et al.’s experiments.23) Zhu et al. have also studied the dielectric response and the size effect under force loading above Cuire’s temperature because the domain walls could be ignored in that case.23) Indeed, many researchers have reported when the pressure is not big (around less than 10 MPa), the dielectric constant becomes bigger with increasing pressure.8,24) This should be because the motions of domain walls will cause the re-distribution of domain configuration. The domains whose polarization directions are perpendicular to pressure will become bigger, and then the average dielectric constant increases. But when the pressure is too big, the motion of domain walls will reach a limited value and show less contribution to dielectric response,25) the distortion of lattice will play a major role in dielectric response.