Colossal permittivity behavior and its origin in rutile (Mg1/3Ta2/3)xTi1-xO2

This work investigates the synthesis, chemical composition, defect structures and associated dielectric properties of (Mg 2+ , Ta 5+ ) co-doped rutile TiO 2 polycrystalline ceramics with nominal compositions of (Mg 2+ 1/3 Ta 5+ 2/3 ) x Ti 1− x O 2 . Colossal permittivity (>7000) with a low dielectric loss (e.g. 0.002 at 1 kHz) across a broad frequency/temperature range can be achieved at x  = 0.5% after careful optimization of process conditions. Both experimental and theoretical evidence indicates such a colossal permittivity and low dielectric loss intrinsically originate from the intragrain polarization that links to the electron-pinned \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\bf{M}}{{\bf{g}}}_{{\bf{T}}{\bf{i}}}^{{\prime}{\prime} }+{{\bf{V}}}_{{\bf{O}}}^{\bullet \bullet }+{\bf{2}}{\bf{T}}{{\bf{a}}}_{{\bf{T}}{\bf{i}}}^{\bullet }+{\bf{2}}{\bf{T}}{{\bf{i}}}_{{\bf{T}}{\bf{i}}}^{\prime}$$\end{document} M g T i′ ′+ V O • • + 2 T a T i • + 2 T i T i ′defect clusters with a specific configuration, different from the defect cluster form previously reported in tri-/pent-valent ion co-doped rutile TiO 2 . This work extends the research on colossal permittivity and defect formation to bi-/penta-valent ion co-doped rutile TiO 2 and elucidates a likely defect cluster model for this system. We therefore believe these results will benefit further development of colossal permittivity materials and advance the understanding of defect chemistry in solids.