Enhanced electrical properties in donor–acceptor co-doped Ba(Ti_0.92Sn_0.08)O₃ ceramics

In this work, lead-free piezoelectric ceramics Ba_0.99Li_0.005Al_0.005(Ti_0.92Sn_0.08)O₃-0.5%MnO₂(BLATS-M) and Ba_0.99Li_0.005Nb_0.005(Ti_0.92Sn_0.08)O₃-0.5%MnO₂(BLNTS-M) were synthesized by a solid-state reaction process. The influence of Li⁺–Al³⁺, Li⁺–Nb⁵⁺ ionic pairs on the microstructure, phase structure and electrical properties of Ba(Ti_0.92Sn_0.08)O₃-0.5%MnO₂(BTS-M) was systematically investigated. An orthorhombic (O) phase structure is obtained in all ceramics at room temperature. Both Li⁺–Al³⁺ and Li⁺–Nb⁵⁺ ionic pairs co-doping can enhance the piezoelectricity of BTS-M ceramic, while the Li⁺–Nb⁵⁺ doped BLNTS-M ceramic exhibits an optimum electrical properties: the piezoelectricity coefficient (d₃₃) = 805 pC/N, the electromechanical coupling coefficient (k_p) = 0.519, the relative permititivity (ε_r) = 31900, the converse piezoelectric coefficient $\left(d_{33}^{\ast }\right)$ = 536 pm/V and the in situ quasi-static d₃₃ with maximum $\left(d_{33}^{\text{max}}\right)$ = 1620 pC/N. The dielectric properties versus DC bias electric field experiments exhibit high dielectric tunability (ƞ_r = 97.78%) and figure of merit (FOM = 20.96) at 100 Hz and room temperature in BLNTS-M ceramic. The results suggest an effective approach to design high-performance piezoelectrics and dielectrics by appropriately selecting the types of donor–acceptor ionic pairs.