Grain-boundary-controlled impedances of electroceramics: Generalized effective-medium approach and brick-layer model

2001 ◽  
Vol 89 (7) ◽  
pp. 3955-3959 ◽  
Author(s):  
Ce Wen Nan ◽  
Xisong Zhou ◽  
Jun Nan ◽  
Junbo Wu
Keyword(s):  
Grain Boundary ◽  
Effective Medium ◽  
Layer Model ◽  
Brick Layer Model ◽  
Effective Medium Approach

scholarly journals Effect of intergranular glass films on the electrical conductivity of 3Y-TZP

1994 ◽  
Vol 9 (5) ◽  
pp. 1228-1240 ◽  
Author(s):  
M. Gödickemeier ◽  
B. Michel ◽  
A. Orliukas ◽  
P. Bohac ◽  
K. Sasaki ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Grain Boundary ◽  
Characteristic Temperature ◽  
Complex Impedance ◽  
Layer Model ◽  
Total Electrical Conductivity ◽  
Intergranular Films ◽  
Brick Layer Model ◽  
Equilibrium Thickness ◽  
Glass Films

The electrical conductivity of 3Y-TZP ceramics containing SiO2 and Al2O3 has been investigated by complex impedance spectroscopy between 500 and 1270 K. At low temperatures, the total electrical conductivity is suppressed by the grain boundary glass films. The equilibrium thickness of intergranular films is 1-2 nm, as derived using the “brick-layer” model and measured by HRTEM. A change in the slope of the conductivity Arrhenius plots occurs at the characteristic temperature Tb at which the macroscopic grain boundary resistivity has the same value as the resistivity of the grains. The temperature dependence of the conductivity is discussed in terms of a series combination of RC elements.

Modeling Grain Boundary Scattering and Thermal Conductivity of Polysilicon Using an Effective Medium Approach

2011 ◽  
Author(s):  
Timothy S. English ◽  
Justin L. Smoyer ◽  
John C. Duda ◽  
Pamela M. Norris ◽  
Thomas E. Beecham ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundary ◽  
Polycrystalline Silicon ◽  
Phonon Scattering ◽  
Effective Medium ◽  
Boundary Scattering ◽  
Total Thermal Conductivity ◽  
New Model ◽  
Grain Boundary Scattering ◽  
Effective Medium Approach

This work develops a new model for calculating the thermal conductivity of polycrystalline silicon using an effective medium approach which discretizes the contribution to thermal conductivity into that of the grain and grain boundary regions. While the Boltzmann transport equation under the relaxation time approximation is used to model the grain thermal conductivity, a lower limit thermal conductivity model for disordered layers is applied in order to more accurately treat phonon scattering in the grain boundary regions, which simultaneously removes the need for fitting parameters frequently used in the traditional formation of grain boundary scattering times. The contributions of the grain and grain boundary regions are then combined using an effective medium approach to compute the total thermal conductivity. The model is compared to experimental data from literature for both undoped and doped polycrystalline silicon films. In both cases, the new model captures the correct temperature dependent trend and demonstrates good agreement with experimental thermal conductivity data from 20 to 300K.

Impedance/Dielectric Spectroscopy of Electroceramics in the Nanograin Regime

2002 ◽  
Vol 756 ◽  
Author(s):  
N. J. Kidner ◽  
B. J. Ingram ◽  
Z. J. Homrighaus ◽  
T. O. Mason ◽  
E. J. Garboczi
Keyword(s):  
Finite Difference ◽  
Grain Boundary ◽  
Boundary Layers ◽  
Volume Fraction ◽  
Layer Model ◽  
Grain Sizes ◽  
Brick Layer Model ◽  
Polycrystalline Ceramics ◽  
Gradient Effects ◽  
Grain Core

ABSTRACTIn the microcrystalline regime, the behavior of grain boundary-controlled electroceramics is well described by the “brick layer model” (BLM). In the nanocrystalline regime, however, grain boundary layers can represent a significant volume fraction of the overall microstructure and simple layer models are no longer valid. This work describes the development of a pixel-based finite-difference approach to treat a “nested cube model” (NCM), which more accurately calculates the current distribution in polycrystalline ceramics when grain core and grain boundary dimensions become comparable. Furthermore, the NCM approaches layer model behavior as the volume fraction of grain cores approaches unity (thin boundary layers) and it matches standard effective medium treatments as the volume fraction of grain cores approaches zero. Therefore, the NCM can model electroceramic behavior at all grain sizes, from nanoscale to microscale. It can also be modified to handle multi-layer grain boundaries and property gradient effects (e.g., due to space charge regions).

scholarly journals On the performance of an ENZ-based sensor using transmission line theory and effective medium approach

2019 ◽  
Vol 21 (4) ◽  
pp. 043056 ◽  
Author(s):  
V Pacheco-Peña ◽  
M Beruete ◽  
P Rodríguez-Ulibarri ◽  
N Engheta
Keyword(s):  
Transmission Line ◽  
Effective Medium ◽  
Transmission Line Theory ◽  
Line Theory ◽  
Effective Medium Approach
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