scholarly journals Effects of Charge Compensation on Colossal Permittivity and Electrical Properties of Grain Boundary of CaCu3Ti4O12 Ceramics Substituted by Al3+ and Ta5+/Nb5+

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3294
Author(s):  
Jakkree Boonlakhorn ◽  
Jedsada Manyam ◽  
Pornjuk Srepusharawoot ◽  
Sriprajak Krongsuk ◽  
Prasit Thongbai
Keyword(s):  
Dielectric Properties ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Barrier Height ◽  
Potential Barrier ◽  
Charge Compensation ◽  
Solid State Reaction Method ◽  
Wide Frequency Range ◽  
Potential Barrier Height

The effects of charge compensation on dielectric and electrical properties of CaCu3Ti4-x(Al1/2Ta1/4Nb1/4)xO12 ceramics (x = 0−0.05) prepared by a solid-state reaction method were studied based on the configuration of defect dipoles. A single phase of CaCu3Ti4O12 was observed in all ceramics with a slight change in lattice parameters. The mean grain size of CaCu3Ti4-x(Al1/2Ta1/4Nb1/4)xO12 ceramics was slightly smaller than that of the undoped ceramic. The dielectric loss tangent can be reduced by a factor of 13 (tanδ ~0.017), while the dielectric permittivity was higher than 104 over a wide frequency range. Impedance spectroscopy showed that the significant decrease in tanδ was attributed to the highly increased resistance of the grain boundary by two orders of magnitude. The DFT calculation showed that the preferential sites of Al and Nb/Ta were closed together in the Ti sites, forming self-charge compensation, and resulting in the enhanced potential barrier height at the grain boundary. Therefore, the improved dielectric properties of CaCu3Ti4-x(Al1/2Ta1/4Nb1/4)xO12 ceramics associated with the enhanced electrical properties of grain boundaries. In addition, the non-Ohmic properties were also improved. Characterization of the grain boundaries under a DC bias showed the reduction of potential barrier height at the grain boundary. The overall results indicated that the origin of the colossal dielectric properties was caused by the internal barrier layer capacitor structure, in which the Schottky barriers at the grain boundaries were formed.

scholarly journals Potential barrier height at the grain boundaries of a poly-silicon nanowire

2015 ◽  
Vol 26 (35) ◽  
pp. 355201 ◽  
Author(s):  
Assaf Shamir ◽  
Iddo Amit ◽  
Danny Englander ◽  
Dror Horvitz ◽  
Yossi Rosenwaks
Keyword(s):  
Grain Boundaries ◽  
Barrier Height ◽  
Potential Barrier ◽  
Silicon Nanowire ◽  
Potential Barrier Height ◽  
Poly Silicon

scholarly journals Significantly Improved Colossal Dielectric Properties and Maxwell—Wagner Relaxation of TiO2—Rich Na1/2Y1/2Cu3Ti4+xO12 Ceramics

Molecules ◽  
2021 ◽  
Vol 26 (19) ◽  
pp. 6043
Author(s):  
Pariwat Saengvong ◽  
Narong Chanlek ◽  
Bundit Putasaeng ◽  
Atip Pengpad ◽  
Viyada Harnchana ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Single Phase ◽  
Solid State Reaction Method ◽  
Molar Ratio ◽  
Boundary Density ◽  
Dense Microstructure ◽  
Mean Grain Size ◽  
The Mean

In this work, the colossal dielectric properties and Maxwell—Wagner relaxation of TiO2–rich Na1/2Y1/2Cu3Ti4+xO12 (x = 0–0.2) ceramics prepared by a solid-state reaction method are investigated. A single phase of Na1/2Y1/2Cu3Ti4O12 is achieved without the detection of any impurity phase. The highly dense microstructure is obtained, and the mean grain size is significantly reduced by a factor of 10 by increasing Ti molar ratio, resulting in an increased grain boundary density and hence grain boundary resistance (Rgb). The colossal permittivities of ε′ ~ 0.7–1.4 × 104 with slightly dependent on frequency in the frequency range of 102–106 Hz are obtained in the TiO2–rich Na1/2Y1/2Cu3Ti4+xO12 ceramics, while the dielectric loss tangent is reduced to tanδ ~ 0.016–0.020 at 1 kHz due to the increased Rgb. The semiconducting grain resistance (Rg) of the Na1/2Y1/2Cu3Ti4+xO12 ceramics increases with increasing x, corresponding to the decrease in Cu+/Cu2+ ratio. The nonlinear electrical properties of the TiO2–rich Na1/2Y1/2Cu3Ti4+xO12 ceramics can also be improved. The colossal dielectric and nonlinear electrical properties of the TiO2–rich Na1/2Y1/2Cu3Ti4+xO12 ceramics are explained by the Maxwell–Wagner relaxation model based on the formation of the Schottky barrier at the grain boundary.

Reversible Force-Resistivity Behavior of Thin Films of the TTF-Tcnq Family

1996 ◽  
Vol 436 ◽  
Author(s):  
W. Vollmann ◽  
H.-U. Sonntag
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Potential Barrier ◽  
Film Plane ◽  
Barrier Width ◽  
Dependent Potential ◽  
Sample Resistance

AbstractThe electrical properties of vacuum sublimed thin films of TTF-TCNQ and its derivatives mainly are determined by electron barriers at grain boundaries. The electrical conductivity is thermal activated and exhibits a significant dependence on a force acting perpenticularly to the film plane. The sample resistance R decreases continiously with increasing force F. TCNQ thin films on steel show a similar R-F relation. The effect has been observed already at forces of 1 N, but also up to about 60 kN. An explanation of these phenomena is given by a grain boundary limited hopping mechanism with pressure dependent potential barrier width and height. Morphology investigations by SEM support the model.

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