Achieving excellent energy storage performance of K1/2Bi1/2TiO3-based ceramics via multi-phase boundary and bandgap engineering

As a latent candidate for energy storage material, K1/2Bi1/2TiO3 (KBT) attracts the interest of researchers due to its high saturation polarization and inherited relaxor feature. But the low dielectric breakdown strength Eb of KBT-based ceramics limits the potential for the dielectric energy storage application. Efficient improving on the Eb while keeping the field-induced polarization difference AP at high level is of significance for designing KBT-based dielectric energy storage ceramics. In this work, by constructing a ferroelectric-relaxor phase boundary in KBT-Na1/2Bi1/2ZrO3 (NBZ) and introducing the recipient ferroelectric SrHfO3 (SH) with wide bandgap, the synergistic improvement on the Eb and AP were realized. Our experimental results reveal that, 0.9KBT-0.1NBZ behaves as a strong ferroelectric relaxor, and SH addition into 0.9KBT-0.1NBZ increases the band gap and suppresses the leakage current, thus enhances the dielectric breakdown strength Eb significantly. At SH addition of 6.0 mol.%, excellent polarization behavior and energy storage performance were achieved: a super-large AP of 47.8 mu C/cm2, an ultrahigh recoverable energy density Wr of 5.33 J/cm3, and a high efficiency above 75%. Our work proposes a novel design route to construct KBT-based ceramics as a candidate for energy storage capacitors.