Dielectric relaxation and electronic structure of Ca ( Fe 1 ∕ 2 Sb 1 ∕ 2 ) O 3

The frequency-dependent dielectric relaxation of calcium-iron-antimonate $[\mathrm{Ca}({\mathrm{Fe}}_{1∕2}{\mathrm{Sb}}_{1∕2}){\mathrm{O}}_{3}]$ (CFS) ceramic, synthesized by a solid-state reaction technique is investigated in the temperature range from $143\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}463\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ by alternating-current impedance spectroscopy. The x-ray diffraction of the sample at room temperature shows a monoclinic phase. Using Cole-Cole model, an analysis of the imaginary part of the dielectric permittivity with frequency is performed assuming a distribution of relaxation times. The activation energy calculated from the frequency dependence of loss spectra is found to be $\ensuremath{\simeq}0.60\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, which suggests that the bulk conduction in CFS is due to polaron hopping based on the electron carriers. The scaling behavior of the imaginary part of the electric modulus $({M}^{\ensuremath{''}})$ suggests that the relaxation describes the same mechanism at various temperatures. We studied the electronic structure of the CFS using x-ray photoemission spectroscopy (XPS). The XPS spectrum was analyzed by the first-principles full-potential linearized augmented plane wave method.