Effect Of Ta Doping Research Articles

Dielectric response of TiO2 ceramics: The crucial role of Ta2O5

Abstract Colossal permittivity in tantalum-doped TiO2 (TaxTi1−xO2) (x = 1%, 2%, 3%, 4%, 5% and 6%) fabricated by the conventional solid-state reaction method in N2 atmosphere were achieved. Especially, by optimizing components and sintering temperatures, the dielectric loss could significantly decreased. The effects of Ta doping on their microstructure, dielectric properties, and temperature stability were revealed in detail. When the composition with x = 5% and sintered at 1400 °C, the dielectric constant reached to ∼30000 and the dielectric loss decreased to 3%. Interestingly, all the samples also exhibit good temperature stability of dielectric properties in a wide temperature range from 100 to 350 K. Based on XPS analysis, the formation of defect-dipole clusters, e.g. 2 ( Ta 5 + ) Ti · → 4 ( Ti 3 + ) Ti ′ ← V o ·· should be mainly responsible for the improved dielectric properties in tantalum-doped TiO2.

Effect of Ta doping on the characteristic features of spray-coated SnO2

In present work, undoped and Ta-doped SnO2 thin films were fabricated via a simple and cheap spray pyrolysis technique. The Ta-doping level was varied from 0at.% to 5at.% in the step of 1at.%. Large pyramidal and small densely-packed tetragonal SnO2 particles were observed by X-ray diffraction and scanning electron microscope. Atomic force microscope analysis indicated that root mean square roughness values of films changed from 26.7nm to 51.6nm with Ta-doping. The electrical and optical measurements revealed that the films had a degenerate n-type semiconductor property. The resistivity, sheet resistance, carrier concentration, mobility, and optical band gap values of films varied between 1.11×10−2Ωcm–2.35×10−3Ωcm, 130.66Ω/□–26.97Ω/□, 2.72×1019cm−3–1.12×1020cm−3, 20.68cm2V−1s−1–30.78cm2V−1s−1, and 3.43eV–3.94eV, respectively. As a result of this study, it is concluded that characteristic properties of SnO2 can be greatly improved with Ta-doping.

Effect of tantalum doping on the structural and optical properties of RF magnetron sputtered indium oxide thin films

Tantalum doped indium oxide films are prepared by RF magnetron sputtering technique and the films are annealed in air at 300°C. The effect of Ta doping on the structural, morphological, and optical properties of the annealed films are studied using techniques like X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), EDX analysis, micro-Raman, UV–visible and photoluminescence spectroscopy and electrical measurements. The XRD patterns present a cubic bixbyite structure for all the films with preferred orientation along the (222) plane. The lattice constant estimation presents a reduction in lattice size with Ta doping. The W–H plot shows a tensile strain for all the films and also indicates the presence of strain induced broadening of the XRD peaks. The Raman spectra present all the characteristic modes of In2O3 cubic bixbyite phase. FESEM and AFM images show the uniform and dense distribution of smaller grains in the films. All the films show high transmittance (above 85%) in the 400–900nm region. Electrical measurement shows a systematic increase of carrier concentration and electrical conductivity with increase in Ta doping concentration. Band gap energy increases with increase in Ta doping concentration. All the films show intense PL emission in the UV region.

Effect of Ta Doping on the Microstructure, Dielectric and Ferroelectric Properties of Sr2Nb2O7 Ceramics

Sr2(TaxNb1-x)2O7 (x = 0.0, 0.1, 0.2, 0.4) (STNO) ceramics were prepared by the conventional solid-state reaction method. The microstructure, dielectric and ferroelectric properties of the samples were investigated. The results show single phase STNO with perovskite-like layered structure and that Ta5+ ion can diffuses into the crystal lattice. The addition of Ta5+ dopant decreases the grain size of the material. The dielectric constant increases with increased x, and the sample with x = 0.2 exhibits enhanced dielectric properties (ϵr ≈ 56, tanδ ≈ 0.01%). The remnant polarization (2Pr) and coercive electric field (2EC) of STNO ceramics increase with increasing Ta content, and reach the maximum value (2Pr = 0.11μC/cm2 and 2EC = 5.75 kV/cm) at x = 0.4. Our results indicate that Ta doping can effectively improve the dielectric and ferroelectric properties of Sr2Nb2O7 ceramics.

The effect of Ta doping in polycrystalline TiOx and the associated thin film transistor properties

Tantalum (Ta) is suggested to act as an electron donor and crystal phase stabilizer in titanium oxide (TiOx). A transition occurs from an amorphous state to a crystalline phase at an annealing temperature above 300 °C in a vacuum ambient. As the annealing temperature increases from 300 °C to 450 °C, the mobility increases drastically from 0.07 cm2/Vs to 0.61 cm2/Vs. The remarkable enhancement of thin film transistor performance is suggested to be due to the splitting of Ti 3d band orbitals as well as the increase in Ta5+ ions that can act as electron donors.

The Effect of Ta Doping on the Phase Transitions and the Piezoelectric and Ferroelectric Properties of K0.35Na0.65NbO3

The ferroelectric, piezoelectric and phase transition behavior of high-density K0.35Na0.65 NbO3 samples prepared by solid state synthesis, and changes in these properties with Ta doping are reported, including improvement of piezoelectric coefficient d 33s. Piezoresponse force microscopy is used to investigate the ferroelectric domain structure. Temperature-dependent resonant ultrasound spectroscopy is used to investigate phase transitions as well as internal friction. Tuning of the monoclinic to tetragonal phase transition to room temperature is predicted at ∼35% Ta doping.

Effect of Ta-doping on the ionic conductivity of lithium titanate

The powders of Li 2Ti 1− x Ta x O 3+ x/2 (0.10 ≤ x ≤ 0.35) were synthesized by a solid-state reaction method and Li 2Ti 1− x Ta x O 3+ x/2 sintered bodies were fabricated with the powders at 1100 °C for 6 h. Phase analysis and microstructure of the samples were determined by XRD and SEM, respectively. Complex electrochemical impedance spectroscopy was used to evaluate the electrical conduction properties of the sintered ceramics. The experimental results showed that Ta 2O 5 could dissolve in Li 2TiO 3 and reached the saturation degree of about 25% at 1100 °C. The doped samples possessed much higher ionic conductivity than the primitive Li 2TiO 3 with the most favorable doping level of 25%. At 300 °C, the ionic conductivity of the doped Li 2Ti 0.75Ta 0.25O 3.125 ( x = 0.25) ceramics achieved 9.00 × 10 −5 S cm −1, more than 2 orders of magnitude higher than that of the primitive Li 2TiO 3 ceramics (7.75 × 10 −7 S cm −1).

Nonlinear electrical characteristics and dielectric properties of Ca,Ta-doped TiO 2 varistors

Ca,Ta-doped TiO2 varistors with high nonlinear coefficients are obtained by a ceramic sintering. The nonlinear electrical and dielectric properties of the samples doped with 0.5mol% Ca and various concentrations of Ta (0.05∼2.0mol%) were investigated. The samples sintered at 1350 °C have nonlinear coefficients of α=5.1∼42.1 and high relative dielectric constants approach 105. The effects of Ta-doping on the nonlinear and dielectric properties of the Ca,Ta-doped TiO2 varistors are studied in greater detail. When the concentration of Ta is 0.5mol%, the sample possesses the highest nonlinear coefficient and a comparatively lower dielectric constant. The effects of Ta and the nonlinear electrical behavior of the TiO2 system are explained by analogy to a grain-boundary atomic defect model.