[(Bi_0.50Na_0.40K_0.10)_0.94Ba_0.06]_1-xLa_xTi_0.975Ta_0.025O₃ lead-free relaxor ceramics with high energy storage density and thermally stable dielectric properties

Dielectric ceramics for capacitors have attained significant attention in current time owing to their large power densities and fast charge/discharge rates. Lead-free [(Bi_0.50Na_0.40K_0.10)_0.94Ba_0.06]_1-xLa_xTi_0.975Ta_0.025O₃ (abbreviated as BNKBTT-100xLa) relaxor ceramics are prepared using mixed-oxide technique. All ceramics are revealed a pseudo-cubic structure using X-ray diffraction technique. The long-range order existing in BNKBTT-100xLa ceramics is found to reduce with increasing composition. As a result, a highly effective energy storage density (W_rec) ~ 1.558 J/cm³ and efficiency (η) ~ 88.46% is achieved in BNKBTT-2La ceramic. In addition, BNKBTT-2La composition is fatigue-free up to 10⁵ cycles. Also, BNKBTT-4La ceramic exhibits a dielectric constant (ε') ~ 2281 near 150 °C with Δε'/ε'_150 °C below 15% over a large range from 39 to 383 °C, showing an outstanding dielectric temperature stability. Therefore, BNKBTT-2La and BNKBTT-4La ceramics are outstanding for energy density and thermally stable dielectric permittivity, respectively, for the device applications.