Dielectric characterizations of alkali niobates Li4(1-x)Na4xKNb5O15 (x=0.25-0.75) ceramics

摘要

Li4(1-x)Na4xKNb5O15 (LNKN, x=0.25, 0.5, 0.625 and 0.75) ceramics were synthesized by conventional solid-state reaction method and studied as composite ceramics. The study considered that the LNKN ceramics are the mixed phase of perovskite (Pe) based (Na, K) NbO3 (NKN), tetragonal tungsten bronze (TTB) based K3Li2Nb5O15 (KLN) and LiNbO3. The effects of mixed phase contribute to the dielectric properties at temperatures around Tmax for the LNKN ceramics. Dielectric maximum occurs at a temperature around Tmax=500℃ irrespective of the Li/Na composition. The largest dielectric maximum εmax was observed in LNKN (x=0.625) ceramics. Dielectric maximum εmax seems to be proportional to the volume fraction of Pe based NKN phase. The second dielectric anomaly occurs at lower temperatures TT-O. The variation of TT-O seems to be caused by the change in Na/K content in the NKN phase.