Enhancement of mechanical and energy storage properties of Ba(Ti0.8Co0.2)O3 Pb-free ceramics by addition of Nd3+ ions

Abstract

Composites of (Ba_1−xNd_x)(Ti_0.8Co_0.2)O₃ (abbreviated as BNTC) (x:0.1, 0.2 and 0.3 mol%) Pb-free ceramics were prepared through a conventional solid-state reaction method. The crystal structure, dielectric, magnetic susceptibility, mechanical and galvanostatic charging properties of prepared ceramics were investigated. A slight shift in diffraction peaks towards the higher angles along with variation in the crystal structure from the orthorhombic phase to the rhombohedral phase was observed with increasing Nd amounts. Significant enhancement in dielectric properties of BNTC was achieved by increasing the amount of Nd. The permittivity (ε_r) and phase transition temperature (T_m) increased from 3947 at 133 °C to 17 710 at 216 °C when the amount of Nd increased from 0.1 to 0.3. The magnetic results revealed that BNTC exhibited a ferromagnetic to paramagnetic phase transition at (T_c) due to the double exchange interaction in Nd³⁺(Co³⁺)O²⁻Nd⁴⁺(Co⁴⁺) bonds. Whereas, antiferromagnetic to ferromagnetic phase transition was observed at (T_N) due to the super-exchange interaction in Nd³⁺(Co³⁺)O²⁻–Nd³⁺(Co³⁺)/Nd⁴⁺(Co⁴⁺)O²⁻Nd⁴⁺(Co⁴⁺). Further, the addition of Nd shows a significant enhancement in mechanical properties and elastic modulus, including Young's modulus (E), longitudinal modulus (L), shear modulus (G), and bulk modulus (K), due to the optimization of the structural properties. Superior enhancement in the charging/discharging time of BNTC ceramics was achieved by increasing the Nd content. The charging/discharging time decreased from 0.146 s to 0.007 s when the amount of Nd increased from 0.1 to 0.3. The present results indicate that the BNTC sample with Nd = 0.3 may be a promising ferromagnetic material for ultrafast charging.