Quasi-intrinsic colossal permittivity in Nb and In co-doped rutile TiO2nanoceramics synthesized through a oxalate chemical-solution route combined with spark plasma sintering
Abstract:Nb and In co-doped rutile TiO2 nanoceramics (n-NITO) were successfully synthesized through a chemical-solution route combined with a low temperature spark plasma sintering (SPS) technique. The particle morphology and the microstructure of n-NITO compounds were nanometric in size. Various techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG)/differential thermal analysis (DTA), Fourier transform infrared (FTIR), and Raman spectroscopy were used for the struct… Show more
“…The two peaks of 206.9 and 209.6 eV are observed for Nb 3 d 5/2 and Nb 3 d 3/2 , respectively. The spacing of 2.7 eV is caused by the spin‐orbit splitting, which is consistent with that of reported co‐doped TiO 2 . Besides, no extra Nd 3 d information from other valence states with low binding energy is found.…”
Effect of isovalent Zr dopant on the colossal permittivity (CP) properties was investigated in (Zr + Nb) co‐doped rutile TiO2 ceramics, i.e., Nb0.5%ZrxTi1−xO2. Compared with those of single Nb‐doped TiO2, the CP properties of co‐doped samples showed better frequency‐stability with lower dielectric losses. Especially, a CP up to 6.4 × 104 and a relatively low dielectric loss (0.029) of x = 2% sample were obtained at 1 kHz and room temperature. Moreover, both dielectric permittivity and loss were nearly independent of direct current bias, and measuring temperature from room temperature to around 100°C. Based on X‐ray photoelectron spectroscopy, the formation of oxygen vacancies was suppressed due to the incorporation of Zrions. Furthermore, it induced the enhancement of the conduction activation energy according to the impedance spectroscopy. The results will provide a new routine to achieve a low dielectric loss in the CP materials.
“…The two peaks of 206.9 and 209.6 eV are observed for Nb 3 d 5/2 and Nb 3 d 3/2 , respectively. The spacing of 2.7 eV is caused by the spin‐orbit splitting, which is consistent with that of reported co‐doped TiO 2 . Besides, no extra Nd 3 d information from other valence states with low binding energy is found.…”
Effect of isovalent Zr dopant on the colossal permittivity (CP) properties was investigated in (Zr + Nb) co‐doped rutile TiO2 ceramics, i.e., Nb0.5%ZrxTi1−xO2. Compared with those of single Nb‐doped TiO2, the CP properties of co‐doped samples showed better frequency‐stability with lower dielectric losses. Especially, a CP up to 6.4 × 104 and a relatively low dielectric loss (0.029) of x = 2% sample were obtained at 1 kHz and room temperature. Moreover, both dielectric permittivity and loss were nearly independent of direct current bias, and measuring temperature from room temperature to around 100°C. Based on X‐ray photoelectron spectroscopy, the formation of oxygen vacancies was suppressed due to the incorporation of Zrions. Furthermore, it induced the enhancement of the conduction activation energy according to the impedance spectroscopy. The results will provide a new routine to achieve a low dielectric loss in the CP materials.
“…Although both defect models, i.e . the EPDD proposed in this work and the hopping charge conduction in localized electrons in the distributed potential well proposed in refs 22 and 23, are quite similar, our case (no Nb 4+ ) differs from the results reported previously 22, 23 where the defects are associated with the existence of Nb 4+ ions.Figure 4The complex permittivity ( ε
* ) plot of 0.5% Mg + Ta co-doped rutile TiO 2 fitted with the Debye model and the Havriliak-Negami (H-N) model.
…”
Section: Resultsmentioning
confidence: 55%
“…This makes reported dielectric properties of In + Nb co-doped rutile TiO 2 very diverse 18–23 . Intrinsically, an excellent CP property with a low dielectric loss can be achieved mainly or at least dominantly from EPDD 20, 21 or from the localized electrons associated with the coexistence of Ti 3+ and Nb 4+ presented in the samples 22, 23 . In contrast, CP behaviors with significantly higher dielectric loss that comes from the extrinsic polarization contribution, e.g.…”
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.
“…The coexistence of giant permittivity and low dielectric loss within a dielectric material is of interest because of the increasing demand for such materials in industrial applications such as high‐energy density devices, dynamic random access memory and microelectronic applications. Many dielectrics with giant permittivity have attracted a great deal of attention and these materials have included CaCu 3 Ti 4 O 12 (CCTO), Ba(Fe 1/2 B 1/2 )O 3 (B = Nb, Ta, and Sb), doped‐NiO, and trivalent cation‐modified SrTiO 3 ceramics .…”
(Nb+Al) co‐doped SrTiO3 ceramics with a nominal composition of Sr(Nb0.5Al0.5)xTi1‐xO3 (x = 0, 0.02, 0.04, and 0.06) were fabricated using the conventional solid‐state reaction method; giant permittivity (10500) and low dielectric loss (0.03) were obtained at x = 0.06. Dielectric and impedance spectroscopy, X‐ray photoelectron spectroscopy, and Raman spectroscopy, were employed to study why the dielectric property improved. The results indicate that the giant dielectric response occurs because of the combined effects of the off‐center Ti3+ reorientation and conduction of electrons with the polar ordering structure Ti3+/Ti4+. In contrast, the low dielectric loss can be attributed to electron localization that occurs because of the defect dipole ][Ti4+·e−Vo··−Ti4+·e. These fundamental understandings will benefit the design of doped SrTiO3 ceramics with desired performance.
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