CRYSTAL STRUCTURE DEPENDENCE OF ELECTRICAL PROPERTIES OF Li_(0.02)(K_(1-x)Na_x)_(0.98)NbO_3 CERAMICS

摘要

Effects of crystal structure on the electrical properties of Li_(0.02)(K_(1-x)Na_x)_(0.98)NbO_3 (0.4 ≤ x ≤ 0.6) ceramics have been investigated. For the specimens sintered at 1030°C for 5 hr, the unit-cell volume was decreased with the increase of NaNbO_3 content. This result could be attributed to the smaller ionic radius of Na~+(0.139 nm) than that of K~+(0.164nm). Dielectric constant and electromechanical coupling factor (k_p) were dependent on the Nb-site bond valences. The mechanical quality factor (Q_m) of the sintered specimen was maximum value of 229 at x=0.5, and then decreased due to the decrease of relative density. The effect of octahedral distortion on the temperature coefficient of k_p (TCk_p) for Li_(0.02)(K_(1-x)Na_x)_(0.98)NbO_3 perovskite structure was also discussed.