Ultrahigh energy storage density in Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃-based lead-free ceramics by introducing a relaxor end-member

Dielectric ceramics with relaxor characteristics are promising candidates to meet the demand for capacitors in next-generation pulse devices. In this work, Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT)-based lead-free ceramics with an ultrahigh recoverable energy storage density (W_rec) were designed and fabricated by introducing the relaxor end-member of Bi(Zn_2/3Ta_1/3)O₃ (BZT). The addition of BZT disrupted the ferroelectric (FE) long-range order and triggered an FE-to-relaxor FE (RFE) phase, leading to the formation of locally polar nano-regions (PNRs) and significantly inhibiting grain growth. Meanwhile, the presence of PNRs with good thermal stability improved the temperature stability of both the dielectric constant (ε') and W_rec. More importantly, the breakdown electric field strength was significantly improved up to ∼640 kV/cm, resulting in an ultrahigh W_rec of ∼7.11 J/cm³ for the 8%BZT doped BCZT (BCZT-BZT8) ceramic. Furthermore, the BCZT-BZT8 ceramic exhibited excellent charge/discharge performances (C_D ∼ 458.4 A/cm², P_D ∼ 50.4 MW/cm³, W_D ∼ 1.354 J/cm³, t_0.9 ∼ 320 ns) with good thermal stability in the temperature range of 298–373 K. The defect chemistry of the BCZT-BZT8 was explored using electron paramagnetic resonance (EPR) spectroscopy which revealed an EPR signal (g ∼ 1.955), associated with oxygen vacancies. The above findings indicate that the novel composition of BCZT-BZT8 has great prospects in energy storage capacitor applications.