Phase Transition and High Piezoelectric Properties of Li_(0.058)(Na_(0.52)+_xK_(0.48))_(0.942)NbO_3 Lead-Free Ceramics

摘要

Highly dense (Li,Na,K)NbO_3 ceramics were prepared by normal sintering at reduced temperatures by adding excessive Na, and its phase structure and electrical properties were investigated as a function of the compensated Na content. A high piezoelectric coefficient d_(33) up to 279 pC/N was obtained at an optimized Na content, which was found to correspond to a phase boundary between two kinds of orthorhombic phases. The corresponding Curie temperature and electromechanical coupling factor reached 465℃ and 46%, respectively. The phase boundary found in the present (Li,Na,K)NbO_3 ceramics like the morphotropic phase boundary existing in the Pb(Zr,Ti)O_3 system, but different from the polymorphic phase transition from an orthorhombic phase to a tetragonal one reported previously in most (Li,Na,K)NbO_3 ceramics.