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)xTi1−xO2. 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 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.

Highly Efficient Visible Light Catalysts Driven by Ti3+‐VO‐2Ti4+‐N3− Defect Clusters

“…Our recent work on the development of highly efficient TiO 2 ‐based VLCs demonstrated the significance of introducing a high but equal concentration of (N 3− , Nb 5+ ) defect pairs for outstanding photocatalytic properties ,. This, in combination with our previous research on (In 3+ , Nb 5+ ), (Al 3+ , Nb 5+ ), (Mg 2+ , Ta 5+ ), (Zn 2+ , Nb 5+ ) and (In 3+ , Ta 5+ ) co‐doped rutile/anatase TiO 2 ceramics/nanocrystals, suggests the complexity of ionic co‐doping in structurally strongly correlated oxides. The introduced extrinsic ions may stay as isolated point defects in host materials and may also form defect‐pairs or clusters coupled with the host ions and local crystal structures.…”

Influence of Zr dopant on polarization in rutile (In0.5Nb0.5)0.005(Ti1‐xZrx)0.995O2 ceramics

“…Thus, multiple Debye‐type relaxations with different τ overlapped each other and show a broad distribution of τ . Different τ resulted in α > 0 when x = 0 . In the rutile INZT ( x > 0) solid solution, Zr 4+ replaces Ti 4+ , which affects the states of localized electrons.…”

Good thermal stability, giant permittivity, and low dielectric loss for X9R‐type (Ag1/4Nb3/4)0.005Ti0.995O2 ceramics

“…In the past decades, giant permittivity materials with a large dielectric constant ( ε r ), low dielectric loss (tanδ), and good thermal stability have attracted much attention due to the requirements for the miniaturization of electronic devices and high‐energy storage capacitors . In 2013, the remarkable dielectric behavior of the materials, In and Nb codoped TiO 2 ‐based ceramics, was reported by Liu et al; these materials showed low dielectric loss (<5%) and large dielectric constant (~10 4 ) and had better temperature stability in the range from 80 to 450 K. Meanwhile, the authors deemed that the origin of the dielectric response was attributed to the intrinsic dielectric effect, that is, the electron pinned defect dipole (EPDD).…”

“…In 2013, the remarkable dielectric behavior of the materials, In and Nb codoped TiO 2 ‐based ceramics, was reported by Liu et al; these materials showed low dielectric loss (<5%) and large dielectric constant (~10 4 ) and had better temperature stability in the range from 80 to 450 K. Meanwhile, the authors deemed that the origin of the dielectric response was attributed to the intrinsic dielectric effect, that is, the electron pinned defect dipole (EPDD). Subsequently, based on the same design idea, a series of codoped TiO 2 ‐based ceramics with better dielectric properties were also obtained for other ions (Ca 2+ , Zn 2+ , Mg 2+ , Sc 3+ , Y 3+ , Al 3+ , In 3+ , Yb 3+ , etc., as acceptors and Nb 5+ , Ta 5+ , etc., as donors) …”

“…Now, the question has arisen as to whether codoping with different donor and acceptor ions could introduce EPDD in the TiO 2 lattice to finally achieve low dielectric loss in TiO 2 ‐based ceramics. Recently, different EPDD configurations have been successfully designed in Mg 2+ /Zn 2+ and Nb 5+ /Ta 5+ codoped TiO 2 , and these samples show high dielectric constant and low dielectric loss . However, Nb and Al codoping could not promote the formation of EPDD and gave rise to a high dielectric loss .…”