Fig. 3 shows the P–E hysteresis loops of KNNLN with different
sintering temperatures. The P–E loops of three kind’s samples are
all well developed. A maximum remnant polarization
(Pr = 22.7 mC/cm2) was obtained for the sample sintered at
1040 8C. Table 1 list the room-temperature electrical parameters
of the three kinds of samples after poling. The same poling
condition (3 kV/mm, 20 min) was used for all samples. The
piezoelectric property of these three kinds’ samples varied
obviously with the sintering temperature. It was found that the
sample of 1040 8C possessed the best piezoelectric parameter
(d33 = 255 pC/N).