3. Results and discussion
Fig. 1 shows the XRD patterns of KNNLN ceramics for different
sintering temperatures. Judging from the FWHM and relative
intensities of (0 0 2) and (2 0 0) peaks, it easily comes to the
conclusion that three kinds’ samples all do not just possess
alternate orthorhombic or tetragonal phase. And they all present a
mixed structure, in which tetragonal (T) and orthorhombic (O)
phase coexist. The previous research indicated that the symmetry
of the phase structure for the KNN-based ceramics can be
distinguished from the value of the I2 0 0/I0 0 2 [12]. However, in
present case this approach does not work well due to the
coexistence of orthorhombic and tetragonal phase in these three
kinds’ samples. However, we could roughly determine the ratio of
orthorhombic and tetragonal phase in the samples by the value of
I2 0 0/I0 0 2. Given that the relationship between the value of I2 0 0/
I0 0 2 and the ratio of orthorhombic phase in mixed structure are in
accordance with liner dependence presented in Fig. 1. Therefore, it
would be easy to obtain the conclusion that the ratio of the
orthorhombic phase increases with the sintering temperature. The
tetragonal phase takes up almost half part for the sample of 980 8C.
The orthorhombic phase becomes dominant with temperature
increased to 1080 8C. It is supposed that the endpoints are pure O
and T phase corresponding with the value of 0.5 and 2, respectively.
And any dot between the two endpoints is equivalent to a
coexistence structure. Further measurement is needed to be
carried out to validate the reliability of this approach.