Structural and electrical properties of lanthanide-doped Bi0.5(Na0.80K0.20)0.5TiO3–SrZrO3 piezoelectric ceramics for energy-storage applications

The present study elucidated that the influence of various lanthanide ions (Ho, Ce, Nd, and Eu) doped in Bi_0.5(Na_0.80K_0.20)_0.5TiO₃–SrZrO₃ (BNKT–SZ) ceramics was synthesized by conventional solid-state reaction technique. Their phase structure, piezoelectric, ferroelectric, dielectric, thermal stability, and energy-storage properties were investigated. The powder X-ray diffraction analysis of ceramics revealed the formation of pure perovskite structure along with the pseudo-cubic phase structure. The microstructural investigation showed variation in grain size due to lanthanide doping. The elemental distribution of the chemical composites of lanthanide-doped ceramic sample was identified by EDX analysis. The remnant polarization (P_r) and maximum polarization (P_max) values for BNKT–SZ ceramic showed the values of 6.78 μC/cm² and 8.68 μC/cm² , respectively, under the electric field of 90 kV/cm. Eu³⁺-doped BNKT–SZ ceramics showed a better energy-storage performance, (W_rec) ~ 0.75 J/cm³ and good temperature stability. Dielectric permittivity of the ceramics was studied as a function of temperature ranging from room temperature to 500 °C in the frequency ranges from 1 to 100 kHz. The piezoelectric coefficient (d₃₃) measured on the poled compositions exhibited a maximum value of 127 pC/N for Ce³⁺. For all compositions, the temperature-dependent piezoelectric coefficient was found to be stable up to the transition temperature. The results indicate that the lanthanide-doped BNKT–SZ ceramics are promising candidates for energy-storage capacitor and piezoelectric applications.