Effects Of A-Site Nonstoichiometry On Dielectric And Piezoelectric Properties Of Pb-Free (Na0.53+Xk0.47)(Nb0.55ta0.45)O-3 Ceramics

(Na0.53+xK0.47)(Nb0.55Ta0.45)O-3 (NKNT) ceramics prepared by a solid state process were investigated at 0 <= x <= 0.02 to determine the effects of Na content in NKNT ceramics. With Na nonstoichiometry, piezoelectric properties were varied but grains were all cube-like perovskites with no impurity phases. Piezoelectric coefficient (d(33)) was sensitive to Na content while polymorphic phase transition (PPT) temperature was not. PPT temperature between orthorhombic and tetragonal phases (TO-T) was around room temperature within the compositional range tested. The highest d(33) obtained was 330 pC/N at Na-0.545 (x = 0.015) increased from 310 pC/N at Na-0.53 (x = 0), which was due to the morphotropic phase boundary (MPB) effect around (Na0.53K0.47) of NKNT ceramics.