scholarly journals Microstructural Evolution and High-Performance Giant Dielectric Properties of Lu3+/Nb5+ Co-Doped TiO2 Ceramics

Molecules ◽  
2021 ◽  
Vol 26 (22) ◽  
pp. 7041
Author(s):  
Noppakorn Thanamoon ◽  
Narong Chanlek ◽  
Pornjuk Srepusharawoot ◽  
Ekaphan Swatsitang ◽  
Prasit Thongbai
Keyword(s):  
Dielectric Properties ◽  
Grain Boundaries ◽  
Dopant Concentration ◽  
Dielectric Behavior ◽  
Second Phase ◽  
Doped Tio2 ◽  
Dielectric Relaxations ◽  
Giant Dielectric ◽  
Second Phase Particles ◽  
Co Doped

Giant dielectric (GD) oxides exhibiting extremely large dielectric permittivities (ε’ > 104) have been extensively studied because of their potential for use in passive electronic devices. However, the unacceptable loss tangents (tanδ) and temperature instability with respect to ε’ continue to be a significant hindrance to their development. In this study, a novel GD oxide, exhibiting an extremely large ε’ value of approximately 7.55 × 104 and an extremely low tanδ value of approximately 0.007 at 103 Hz, has been reported. These remarkable properties were attributed to the synthesis of a Lu3+/Nb5+ co-doped TiO2 (LuNTO) ceramic containing an appropriate co-dopant concentration. Furthermore, the variation in the ε’ values between the temperatures of −60 °C and 210 °C did not exceed ±15% of the reference value obtained at 25 °C. The effects of the grains, grain boundaries, and second phase particles on the dielectric properties were evaluated to determine the dielectric properties exhibited by LuNTO ceramics. A highly dense microstructure was obtained in the as-sintered ceramics. The existence of a LuNbTiO6 microwave-dielectric phase was confirmed when the co-dopant concentration was increased to 1%, thereby affecting the dielectric behavior of the LuNTO ceramics. The excellent dielectric properties exhibited by the LuNTO ceramics were attributed to their inhomogeneous microstructure. The microstructure was composed of semiconducting grains, consisting of Ti3+ ions formed by Nb5+ dopant ions, alongside ultra-high-resistance grain boundaries. The effects of the semiconducting grains, insulating grain boundaries (GBs), and secondary microwave phase particles on the dielectric relaxations are explained based on their interfacial polarizations. The results suggest that a significant enhancement of the GB properties is the key toward improvement of the GD properties, while the presence of second phase particles may not always be effective.

Nonlinear current-voltage and giant dielectric properties of Al3+ and Ta5+ co-doped TiO2 ceramics

2019 ◽  
Vol 116 ◽  
pp. 137-142 ◽  
Author(s):  
Wattana Tuichai ◽  
Supamas Danwittayakul ◽  
Narong Chanlek ◽  
Prasit Thongbai
Keyword(s):  
Dielectric Properties ◽  
Doped Tio2 ◽  
Giant Dielectric ◽  
Current Voltage ◽  
Co Doped

scholarly journals High-Performance Giant Dielectric Properties of Cr3+/Ta5+ Co-Doped TiO2 Ceramics

ACS Omega ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 1901-1910
Author(s):  
Wattana Tuichai ◽  
Supamas Danwittayakul ◽  
Narong Chanlek ◽  
Masaki Takesada ◽  
Atip Pengpad ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
High Performance ◽  
Doped Tio2 ◽  
Giant Dielectric ◽  
Co Doped

Giant Dielectric Properties of Ga3+–Nb5+ Co-doped TiO2 Ceramics Driven by the Internal Barrier Layer Capacitor Effect

Materialia ◽  
2021 ◽  
pp. 101175
Author(s):  
Wattana Tuichai ◽  
Supamas Danwittayakul ◽  
Jedsada Manyam ◽  
Narong Chanlek ◽  
Masaki Takesada ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Barrier Layer ◽  
Doped Tio2 ◽  
Internal Barrier ◽  
Giant Dielectric ◽  
Internal Barrier Layer Capacitor ◽  
Co Doped

scholarly journals Enhanced giant dielectric properties and improved nonlinear electrical response in acceptor-donor (Al3+, Ta5+)-substituted CaCu3Ti4O12 ceramics

2021 ◽  
Author(s):  
Jakkree Boonlakhorn ◽  
Narong Chanlek ◽  
Jedsada Manyam ◽  
Pornjuk Srepusharawoot ◽  
Sriprajak Krongsuk ◽  
...  
Keyword(s):  
Grain Size ◽  
Dielectric Properties ◽  
Synergistic Effects ◽  
Electrical Response ◽  
Nonlinear Coefficient ◽  
Dielectric Behavior ◽  
Partial Substitution ◽  
Nonlinear Properties ◽  
Giant Dielectric ◽  
Co Doped

AbstractThe giant dielectric behavior of CaCu3Ti4O12 (CCTO) has been widely investigated owing to its potential applications in electronics; however, the loss tangent (tanδ) of this material is too large for many applications. A partial substitution of CCTO ceramics with either Al3+ or Ta5+ ions generally results in poorer nonlinear properties and an associated increase in tanδ (to ∼0.29–1.15). However, first-principles calculations showed that self-charge compensation occurs between these two dopant ions when co-doped into Ti4+ sites, which can improve the electrical properties of the grain boundary (GB). Surprisingly, in this study, a greatly enhanced breakdown electric field (∼200–6588 V/cm) and nonlinear coefficient (∼4.8–15.2) with a significantly reduced tanδ (∼0.010–0.036) were obtained by simultaneous partial substitution of CCTO with acceptor-donor (Al3+, Ta5+) dopants to produce (Al3+, Ta5+)-CCTO ceramics. The reduced tanδ and improved nonlinear properties were attributed to the synergistic effects of the co-dopants in the doped CCTO structure. The significant reduction in the mean grain size of the (Al3+, Ta5+)-CCTO ceramics compared to pure CCTO was mainly because of the Ta5+ ions. Accordingly, the increased GB density due to the reduced grain size and the larger Schottky barrier height (Φb) at the GBs of the co-doped CCTO ceramics were the main reasons for the greatly increased GB resistance, improved nonlinear properties, and reduced tanδ values compared to pure and single-doped CCTO. In addition, high dielectric constant values (ε′ ≈ (0.52–2.7) × 104) were obtained. A fine-grained microstructure with highly insulating GBs was obtained by Ta5+ doping, while co-doping with Ta5+ and Al3+ resulted in a high Φb. The obtained results are expected to provide useful guidelines for developing new giant dielectric ceramics with excellent dielectric properties.

Permittivity boosting in “yellow” (Nb + In) co-doped TiO2

2020 ◽  
Vol 8 (39) ◽  
pp. 13627-13631
Author(s):  
Hiroki Taniguchi ◽  
Daiki Sato ◽  
Akitoshi Nakano ◽  
Ichiro Terasaki
Keyword(s):  
Dielectric Properties ◽  
Doped Tio2 ◽  
Post Annealing ◽  
Co Doped

Unusual effects of post annealing on optical and dielectric properties of (Nb0.5In0.5)0.01Ti0.99O2 (NITO-1.0%) are reported in the present study.

Cavity of Al-Cu-Mg Alloy during Superplastic Deformation

2007 ◽  
Vol 551-552 ◽  
pp. 645-650
Author(s):  
Min Wang ◽  
Hong Zhen Guo ◽  
Y.J. Liu
Keyword(s):  
Strain Rate ◽  
Grain Boundaries ◽  
Superplastic Deformation ◽  
Room Temperature ◽  
Mg Alloy ◽  
Deformation Condition ◽  
Second Phase ◽  
Rate Condition ◽  
Second Phase Particles ◽  
Strain Rate Condition

According to the characteristic of appearing cavitation in the metals during superplastic deformation, the influence of strain rate on cavity evolvement, the influence of cavity on superplastic deformation capability, and the formation, development process of cavity were investigated for Al-Cu-Mg alloy (i.e. coarse–grained LY12). The results show that: ①The pore nucleation occurs not only at triangle grain boundaries, but also along nearby the second phase particles, and even within grains. The cavities at the triangle grain boundaries are present in V-shape, others near the second phase particles and within grains are present in O-shape. These cavities may result from disharmony slippage of grain boundaries. ②The tendency of cavity development decreases with increasing of strain-rate. In lower strain-rate condition, though Al-Cu-Mg alloy has better superplasticity, many big cavities in the specimen may reduce the room temperature properties of the alloy. In higher strain-rate condition, Al-Cu-Mg alloy has certain superplasticity and room temperature properties as well as few cavities forming. By analyzing, viscous layer on grain boundaries is very thin and grain sizes can be refined during their extruding and rotating each other in higher strain-rate superplastic deformation condition. ③Growth and coalescence of cavity are the main reason of the superplastic fracture of Al-Cu-Mg alloy. And small and a certain amount of cavities with dispersion and independence state are very useful to crystal boundary slippage.

Continuous and Discontinuous Recrystallization of 6013 Aluminum Alloy

2013 ◽  
Vol 753 ◽  
pp. 221-224 ◽  
Author(s):  
Krzysztof Sztwiertnia ◽  
Magdalena Bieda ◽  
Anna Korneva
Keyword(s):  
Aluminum Alloy ◽  
Grain Boundaries ◽  
Second Phase ◽  
Sheet Plane ◽  
Temperature Range ◽  
Orientation Mapping ◽  
Second Phase Particles ◽  
The Matrix ◽  
Continuous Recrystallization

In situ orientation mapping using TEM and calorimetric measurements were carried out to investigate the annealing behavior of cold-rolled 6013 aluminum alloy. The recrystallization of the material can be considered to be a number of processes that correspond to two separate stored energy release peaks. In the temperature range of the peak 1, the deformation zones around the large second-phase particles acted as sites for particle-stimulated nucleation. In the matrix, at the same time, some elongation of grains occurred. The elongated matrix grains appeared because of the reduction of the dislocation density and the annihilation of some low-angle grain boundaries between chains of subgrains lying in layers parallel to the sheet plane. The matrix processes in this temperatures range can be considered forms of continuous recrystallization. The matrix high-angle grain boundaries started to migrate at the temperature range of the peak 2. They moved mostly in the direction normal to the sheet plane. Heating of the sample for an appropriate time at those temperatures resulted in the complete discontinuous recrystallization of the material. The recrystallized microstructure was dominated now by elongated grains, which were a few times thicker than those obtained by annealing at the temperatures of the peak 1.

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