Influence of B-site non-stoichiometry on structure and electrical properties of KNLNS lead-free piezoelectric ceramics

In the present work, the dependence of microstructure and electrical properties on B-site non-stoichiometry (excess) for (Na _0.474K _0.474Li _0.052)(Nb _0.948Sb _0.052)O ₃ - xTa ₂O ₅ (KNLNSTx) was symmetrically investigated. The phase structure was pure perovskite when x < 0.02 mol. While x > 0.02 mol, a secondary phase would be found in the samples. The results indicate that the densification and piezoelectricity were promoted as x < 0.01 mol. It is supposed that the low amount of Ta could induce A-site vacancy and favor the poling efficiency. KNLNSTx ceramics with x = 0.005 mol Ta ₂O ₅ have optimum electrical properties: d ₃₃ = 253 pC/N, k _p = 0.437, Q _m = 43 and tanδ = 0.027.