The powders were dried and pressed into disks,using polyvinyl butyral (PVB) as binder. After PVB was burnt off,
the sintering of the samples were carried out at 9808, 10408 and
1080 8C for 2 h in air. The sintered specimens were coated with
silver paste on both sides as electrodes and poled along c-direction
in a silicone oil bath. As knows that the optimum poling
temperature (Tp) of KNNLN ceramics should be chosen near the
polymorphic phase transition (abbreviated as PPT) temperature
[10]. However, in order to keep the consistence of poling condition,
samples are all poled at room temperature under a dc electric field
of 3 kV/mm for 20 min.