Relationships between crystal structure and electrical properties of Li0.055[Agx(K0.5Na0.5)1−x]0.945(Nb1−yTay)O3 ceramics

Electrical properties of perovskite Li0.055[Agx(K0.5Na0.5)1−x]0.945(Nb1−yTay)O3 (0.00 ≤ x ≤ 0.04, 0.01 ≤ y ≤ 0.09) ceramics were investigated based on the structural characteristics. A morphotropic phase boundary (MPB) between orthorhombic and tetragonal phase was detected through the entire range of compositions. With increasing of Ta5+ content, the dielectric constant (ɛr), piezoelectric coefficient (d33) and electromechanical coupling factor (kp) of Li0.055(K0.5Na0.5)0.945(Nb1−yTay)O3 ceramics were increased up to y = 0.07 and then decreased, while mechanical quality factor (Qm) was increased. However, the ɛr, d33, kp and Qm of Li0.055[Agx(K0.5Na0.5)1−x]0.945(Nb0.07Ta0.03)O3 ceramics were not changed remarkably with Ag+ content. The dependence of temperature coefficient of kp (TCkp) on the oxygen octahedral distortion was also discussed by Raman-active vibrations modes.