SEM images of ceramic samples. Panels (a), (b), (c), and (d) correspond to undoped and 2%, 5%, and 6% , respectively.
Surface EDS mapping of -doped CCTO ceramic samples. Panels (a) and (b) correspond to 5% and 6% , respectively.
XRD of undoped and doped CCTO samples. Peaks for the major phase and secondary ones are indicated.
Frequency dependence of the real dielectric permittivity for undoped and -doped CCTO samples.
Cole–Cole ( vs ) plots for the studied samples.
Peak relaxation frequencies for several concentrations up to 6%.
Room-temperature FTIR-reflectivity spectra of the samples. The spectra are vertically upshifted for the sake of clarity (0.2 steps).
Real part of the optical conductivity calculated from KK analysis for the samples in the infrared region. The modes are numbered in agreement with Table I. The vertical dashed lines intend to show frequency shifts for some chosen peaks.
Infrared polar phonon modes obtained for CCTO undoped sample by KK integration of its room-temperature spectrum. TO (transverse) and LO (longitudinal) optical modes were obtained from peak positions of and , respectively. The two last columns give the values reported by Kant et al. for a single crystal at 5 K (Ref. 20).
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