Defect dipoles and electrical properties of magnesium B-site substituted sodium potassium niobates

K0.5Na0.5Nb1−xMgxO3−3x/2 ceramics with the Mg2+ acceptor substitution for the B-site Nb5+ were prepared by using the solid-state reaction process. K0.5Na0.5Nb0.99Mg0.01O2.985 (x = 0.01) had the most pronounced double-loop-like characteristic due to the restoring force provided by the defect polarization (PD) associated with non-centric distributing the defect dipoles (MgNb‴-VO)′, and the Rietveld refinement confirmed that it crystallized in the orthorhombic space group Bmm2 [a = 5.64306(7) Å, b = 3.94541(4) Å and c = 5.67406(7) Å] at room temperature. Furthermore, the P-E loops of K0.5Na0.5Nb0.99Mg0.01O2.985 dependence on annealing, aging, measuring frequency and measuring temperature were investigated, and the reinforcement in the double-loop-like characteristic was caused by a decrease in oxygen concentration, an increase in aging temperature, an increase in measuring frequency and a decrease in measuring temperature.