Electrical and Physical Properties of Lead-Free (Na_(0.5)K_(0.5))NbO_3-Bi_(0.5)(Na_(0.93)K_(0.07))_(0.5)TiO_3 Ceramics

摘要

Extending the investigations on (Na_(0.5)K_(0.5))NbO_3-based solid solution for lead-free piezoelectric ceramics, this paper consider the complex solid-solution system (Na_(0.5)K_(0.5))NbO_3-Bi_(0.5)(Na_(0.93)K_(0.07))_(0.5)TiO_3 [NKN-BNKT]. (Na_(0.5)K_(0.5))NbO_3with 2～6 mol% Bi_(0.5)(Na_(0.93)K_(0.07))_(0.5)TiO_3 has been prepared following the conventional mixed oxide process. A morphotropic phase boundary (MPB) between orthorhombic (O) and rhombohedral (R) was found at the composition 0.98NKN-0.02BNKT with correspondingly enhanced dielectric and piezoelectric properties. The electromechanical coupling factor and dielectric constant are higher for compositions near the MPB. The dielectric constant (K_(33)~T), planar coupling coefficient (k_p) and thickness coupling coefficient (k_t)of 0.98NKN-0.02BNKT ceramics were 1040, 47% and 48%, respectively.