Dong, WenChen, DehongHu, WanbiaoFrankcombe, TerryChen, HuaZhou, ChaoFu, ZhenxiaoWei, XiayongXu, ZhuoLiu, ZhifuLi, YongxiangLiu, Yun2020-12-202020-12-202045-2322http://hdl.handle.net/1885/217913This 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.application/pdfen-AU201710.1038/s41598-017-08992-x2020-11-23