Effect of Yb₂O₃ doping on energy storage and dielectric properties of barium titanate based ceramics

To produce high-performance dielectric capacitors for pulsed power applications, BaTiO₃@(MgO–Nb₂O₅)–xYb₂O₃ (BT@MNY-x) ceramics were prepared via solid-state reaction route. The BT@MNY ceramics retained tetragonal perovskite structure without other obvious phases. Profound structural tests by Rietveld refinement of XRD patterns verified Yb³⁺ substituted the Ti⁴⁺ sites. In addition, after Yb³⁺ ions were incorporated into the lattice of barium titanate, the cubic phase of barium titanate was slightly distorted, the lattice constant of the sample gradually increased, and the tetragonality of the sample gradually decreased. With the increase of Yb₂O₃ content, the porosity and the diffuseness degree (γ) of the ceramics first decreased and then increased, reaching the peak values in the BT@MNY-0.5 sample. In addition, the grain size and dielectric constant of the samples decreased with the increase of Yb₂O₃ content. As a result, the breakdown voltage of the ceramics and performance metrics such as effective energy storage density first increased and then decreased. The calculated activation energies (E_a = 0.9–1.1 eV) closely resemble those observed for oxygen vacancy conduction activation energy in perovskite systems (around 1 eV), indicating that the conductivity in the BT@MNY ceramics is likely governed by oxygen vacancies. When x = 0.5, environmentally friendly barium titanate-based ceramics with W_rec of 0.82 J/cm³ and η of 44.34% were achieved. This work provides a theoretical basis for high energy storage barium titanate ceramics.