<p>Dense KSr₂Nb₅O₁₅ (KSN) ceramics were prepared by tape casting process using the powder as raw materials, which was fabricated by the traditional solid-state reaction method. It was found that the high density of pure KSN ceramics was attributed to the presence of connected pores and formation of a large number of low-energy grain boundaries. The Bi₂O₃ dopant into the KSN ceramics could reduce the anisotropy of grain boundary energy and form liquid phase during sintering, which had a direct effect on the elimination of pores and grain growth behavior. The room-temperature permittivity increased linearly and the dielectric peak broaden accordingly with the increase of Bi₂O₃ content. In addition, pinched ferroelectric hysteresis loops were observed in the pure KSN ceramics, which only occurred in the ferroelectric ceramics doped with high-valent ions. A possible mechanism related reversible domain switching process was proposed. This work give the guidance for the preparation of dense ferroelectric ceramics, also provide the experimental basis for the development of the pinning effect on ferroelectric domain wall.</p>