Abstract:Colossal permittivity properties were studied in Zn,Nb co-doped TiO 2 with different phase structures. The (Zn 1/3 Nb 2/3 ) 0.05 Ti 0.95 O 2 rutile ceramics were prepared by the solid state sintering technique, while the amorphous and anatase films were respectively fabricated by a pulsed laser deposition method and a subsequent rapid thermal annealing. The ceramics showed a frequency (10 2 -10 6 Hz) independent dielectric response with a colossal dielectric permittivity (B30 000), and a relatively low dielect… Show more
“…Two further higher-energy peaks at 532.5 eV and at 531.5 eV are assigned to the presence of oxygen vacancies and surface hydroxyl, respectively 33 . These results suggests the Ta 5+ to be responsible for the reduction of Ti 4+ to Ti 3+ , which is consistent with previously reported results 9 and also quite similar to that of the M + Nb co-doped rutile TiO 2 (M = In, Ga, Zn), where Nb 5+ substitutions locally induce the reduction of Ti 4+ into Ti 3+
1, 13, 14 . Therefore, EPDDs may also similarly form to account for the excellent dielectric properties, detailed below.Figure 1Valence states and defect characterization of Mg + Ta co-doped rutile TiO 2 .…”
Section: Resultssupporting
confidence: 92%
“…A small co-doping level of 0.5% created relatively stable colossal permittivity over 7000, with dielectric loss below 1% (e.g. as low as 0.002 at 1 kHz) in a broad frequency range up to 0.13 MHz, which is low compared with reported co-doped rutile TiO 2 materials and also comparable to reported results for commercially used capacitors 1, 9, 13, 34, 35 . The surface effects were observed in 0.5% Mg + Ta co-doped rutile TiO 2 , with only small variations in dielectric properties using Ag or Pt electrodes (Figure S2a).…”
Section: Resultssupporting
confidence: 83%
“…Actually, the formation of EPDD in the host material is complicated since the formation of defect states is generally strongly related to the dopant ions, and to the preparation approach and conditions. The understanding of EPDD is still at an early stage, with research to date being mainly focused on trivalent acceptor and pentavalent donor co-doped rutile TiO 2
3, 9, 10 , although some primary works, such as Zn + Nb co-doped rutile TiO 2
13 , have been done in bi-/pent-valent doped rutile TiO 2 . Defect structures are related to the ionic sizes, charges and electronegativity of the dopants.…”
Section: Introductionmentioning
confidence: 99%
“…13 , by which the authors mainly focused on the dielectric properties of (Zn, Nb) co-doped TiO 2 with different forms, including rutile ceramics, amorphous films and anatase films, and only proposed the possible defects for CP effect. After further more work done afterwards, we realized that the complexity of defects in those ionic co-doped TiO 2 is critical and the defect formation are the factors to determine the individual dielectric behavior.…”
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.
“…Two further higher-energy peaks at 532.5 eV and at 531.5 eV are assigned to the presence of oxygen vacancies and surface hydroxyl, respectively 33 . These results suggests the Ta 5+ to be responsible for the reduction of Ti 4+ to Ti 3+ , which is consistent with previously reported results 9 and also quite similar to that of the M + Nb co-doped rutile TiO 2 (M = In, Ga, Zn), where Nb 5+ substitutions locally induce the reduction of Ti 4+ into Ti 3+
1, 13, 14 . Therefore, EPDDs may also similarly form to account for the excellent dielectric properties, detailed below.Figure 1Valence states and defect characterization of Mg + Ta co-doped rutile TiO 2 .…”
Section: Resultssupporting
confidence: 92%
“…A small co-doping level of 0.5% created relatively stable colossal permittivity over 7000, with dielectric loss below 1% (e.g. as low as 0.002 at 1 kHz) in a broad frequency range up to 0.13 MHz, which is low compared with reported co-doped rutile TiO 2 materials and also comparable to reported results for commercially used capacitors 1, 9, 13, 34, 35 . The surface effects were observed in 0.5% Mg + Ta co-doped rutile TiO 2 , with only small variations in dielectric properties using Ag or Pt electrodes (Figure S2a).…”
Section: Resultssupporting
confidence: 83%
“…Actually, the formation of EPDD in the host material is complicated since the formation of defect states is generally strongly related to the dopant ions, and to the preparation approach and conditions. The understanding of EPDD is still at an early stage, with research to date being mainly focused on trivalent acceptor and pentavalent donor co-doped rutile TiO 2
3, 9, 10 , although some primary works, such as Zn + Nb co-doped rutile TiO 2
13 , have been done in bi-/pent-valent doped rutile TiO 2 . Defect structures are related to the ionic sizes, charges and electronegativity of the dopants.…”
Section: Introductionmentioning
confidence: 99%
“…13 , by which the authors mainly focused on the dielectric properties of (Zn, Nb) co-doped TiO 2 with different forms, including rutile ceramics, amorphous films and anatase films, and only proposed the possible defects for CP effect. After further more work done afterwards, we realized that the complexity of defects in those ionic co-doped TiO 2 is critical and the defect formation are the factors to determine the individual dielectric behavior.…”
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.
“…Since the discovery of TINO, a series of co-doped rutiles, such as (Sm + Ta), 8 (Zn + Nb) 9 , (Al + Nb) 10 , (Bi + Nb) 11 , (In + Ta) 12 and (Ga + Nb) 13 doped TiO 2 , have been investigated and found to have CP behavior. Liu et al .…”
(In + Nb) co-doped TiO2 (TINO) rutile is an emerging material with a colossal dielectric permittivity (CP) and a low dielectric loss over wide temperature and frequency ranges. The electrical inhomogeneous nature of TINO ceramics is demonstrated by direct local current probing with high-resolution conductive atomic force microscopy (cAFM). The CP response in TINO is found to originate from the electron-pinned defect dipole induced conductive cluster effect and the electrode effect. Two types of dielectric relaxations are simultaneously observed due to these two effects. With the given synthesis condition, we found TINO shows a highly leaky feature that impairs its application as a dielectric material. However, the fast-temperature-rising phenomenon found in this work may open a new door for TINO to be applied as a potential electrothermal material with high efficiency, oxidation-proof, high temperature stability, and energy saving.
Ever since the beginning of this century, many kinds of materials have been reported to demonstrate colossal permittivity (CP) or colossal dielectric constant exceeding 10 3 . Accordingly, such CP materials and their further modification and improvement to achieve enhanced CP performance for promising applications in modern electronics, sensors, energy storage, and multifunctional devices and so on have attracted extensive attention. In this review, 2 a general overview of the recent advances in CP materials is provided, ranging from their various categories, physical mechanisms, and modulation methods to promising applications.First, various classes of CP materials are categorized in terms of their structures and dielectric properties. Subsequently, this review provides an insight into the CP mechanisms in views of barrier layer capacitance, defect-dipole cluster and polaronic effect. Moreover, the strategies and prototypical works are introduced in some aspects, including the manipulation of CP properties by doping, percolative capacitors and the methods employed to enhance the dielectric behaviors in CP materials with different forms. We then discuss a wide range of applications based on CP materials, such as modern electronics and energy storage. Finally, the challenges and opportunities for further investigation of CP materials are highlighted in the summary and future perspectives.
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