Influences of morphotropic phase boundaries on physical properties in (K,Na,Li)Nb0.80Ta0.20O3ceramics

Lead-free (K x Na 1− x ) 1− y Li y Nb 0.80 Ta 0.20 O 3 ceramics have been prepared using the conventional solid-state reaction technique in ambience. A systematic study was carried out to examine the existence and influences of two speculated morphotropic phase boundaries (MPBs). The result shows that the widely-accepted MPB near x = 0.50 can be hardly recognized. All the (K x Na 1− x ) 0.97 Li 0.03 Nb 0.80 Ta 0.20 O 3 ceramics with x = 0.40–0.60 exhibit the high performance of piezoelectric constant d 33 ∼ 230 pC N −1 , planar electromechanical coupling coefficient k p ∼ 48.5% and thickness coupling coefficient k t over 36%. In contrast, the other MPB associating with the Li-content in a narrow compositional width of y = 0.03–0.04 shows a significant influence on the dielectric and piezoelectric properties. Similarity between the latter MPB and that in Pb(Zr,Ti)O 3 is also discussed.