Oxygen-vacancy-related relaxation and scaling behaviors ofBi0.9La0.1Fe0.98Mg0.02O3ferroelectric thin films

Abstract

Oxygen-vacancies-related dielectric relaxation and scaling behaviors of ${\text{Bi}}_{0.9}{\text{La}}_{0.1}{\text{Fe}}_{0.98}{\text{Mg}}_{0.02}{\text{O}}_{3}$ (BLFM) thin film have been investigated by temperature-dependent impedance spectroscopy from $40\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ up to $200\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$. We found that hopping electrons and single-charged oxygen vacancies $({V}_{\text{O}}^{\ifmmode\bullet\else\textbullet\fi{}})$ coexist in the BLFM thin film and make contribution to dielectric response of grain and grain boundary, respectively. The activation energy for ${V}_{\text{O}}^{\ifmmode\bullet\else\textbullet\fi{}}$ is shown to be 0.94 eV in the whole temperature range investigated whereas the distinct activation energies for electrons are 0.136 eV below $110\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ and 0.239 eV above $110\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ in association with hopping along the ${\text{Fe}}^{2+}\text{\ensuremath{-}}{V}_{\text{O}}^{\ifmmode\bullet\else\textbullet\fi{}}{\text{-Fe}}^{3+}$ chain and hopping between ${\text{Fe}}^{2+}{\text{-Fe}}^{3+}$, respectively, indicating different hopping processes for electrons. Moreover, it has been found that hopping electrons are in the form of long-range movement while localized and long-range movement of oxygen vacancies coexist in BLFM film. The Cole-Cole plots in modulus formalism show a polydispersive nature of relaxation for oxygen vacancies and a single relaxation time for hopping electrons. The scaling behavior of modulus spectra further suggests that the distribution of relaxation times for oxygen vacancies is temperature independent.