Piezoelectric and Electeical Properties of Lead-Free (Na_(0.5)K_(0.5))NbO_3-Bi_(0.5)CNa_(0.80)K_(0.20))_(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_(0.80)K_(0.20))_(0.5)TiO_3 [NKN-BNKT]. (Na_(0.5)K_(0.5))NbO_3 with 2-6 mol% Bi_(0.5)(Na_(0.80)K_(0.20))_(0.5)TiO_3 has been prepared following the conventional mixed oxide process. A morphotropic phase boundary (MPB) between orthorhombic (O) and tetragonal (T) was found at the composition 0.97NKN-0.03BNKT with correspondingly enhanced dielectric and piezoelectric properties. The electromechanical coupling factor and dielectric constant are higher for compositions near the MPB. The dielectric constant (ε_r), planar coupling coefficient (k_p) and thickness coupling coefficient (k_t)of 0.97NKN-0.03BNKT ceramics were 1483, 32% and 31%, respectively.