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

Abstract

This work investigates the synthesis, chemical composition, defect structures and associated dielectric properties of (Mg2+, Ta5+) co-doped rutile TiO2 polycrystalline ceramics with nominal compositions of (Mg2+1/3Ta5+2/3) x Ti1−x O2. 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 Mg''Ti+V∙∙O+2Ta∙Ti+2Ti′TiMgTi′′+VO••+2TaTi•+2TiTi′ defect clusters with a specific configuration, different from the defect cluster form previously reported in tri-/pent-valent ion co-doped rutile TiO2. This work extends the research on colossal permittivity and defect formation to bi-/penta-valent ion co-doped rutile TiO2 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. Show more