*2.2. Sample Characterization*

The phase structure for the samples were characterized through X-ray diffraction measurement (XRD, DX–2700B, Haoyuan Instrument, Dandong, China). The nature surfaces of the samples were observed using scanning electron microscope (SEM, Quanta FEG 250, FEI, Waltham, MA, USA). In the frequency range of 100~10<sup>6</sup> Hz, the dielectric properties were measured (room temperature ~700 ◦C) by an LCR meter (TH2829A, Tonghui Electronic, Changzhou, China) and the high temperature conductivity and complex impedance behavior were analyzed.
