Uniaxial stress dependence of the dielectric properties in the Na0.5Bi0.5TiO3–NaTaO3 system

2010 ◽  
Vol 25 (9) ◽  
pp. 1784-1792 ◽  
Author(s):  
Jakob König ◽  
Matjaž Spreitzer ◽  
Boštjan Jančar ◽  
Julian Tolchard ◽  
Mari-Ann Einarsrud ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Time Dependence ◽  
Dielectric Response ◽  
Uniaxial Stress ◽  
Stress Sensitivity ◽  
Time Dependent ◽  
Stress Dependence ◽  
Time Component ◽  
Domain State ◽  
Uniaxial Compressive Stress

The dependence of the dielectric properties on the uniaxial compressive stress and the stress-strain properties was investigated for the case of (1-x)Na0.5Bi0.5TiO3–xNaTaO3 ceramics. Special attention was focused on the time component and the reversibility of the permittivity–stress dependence. The results were interpreted according to the samples' polar and symmetry states and the ferroelasticity. The time dependence and irreversible changes of the dielectric properties were connected with the domain structure of the materials, which is modified under the applied stress. The irreversible changes observed in the macroscopically nonferroelectric compositions were related to the ferroelastic properties. The stress sensitivity increased with the addition of NaTaO3 from 3% in pure Na0.5Bi0.5TiO3 to 14% in the sample with 15 mol% of NaTaO3 (at 200 MPa and 1 MHz). The reversibility was improved by mechanical modification of the samples' domain state, while the dielectric response remained time dependent.

Stress Dependence of Dielectric Properties in Relaxor Ferroelectrics: Monte Carlo Investigation

2009 ◽  
Vol 421-422 ◽  
pp. 227-230 ◽  
Author(s):  
Yongyut Laosiritaworn ◽  
Rattikorn Yimnirun ◽  
Ruyan Guo ◽  
A.S. Bhalla
Keyword(s):  
Monte Carlo ◽  
Dielectric Properties ◽  
Dielectric Permittivity ◽  
Spin Glass ◽  
Frequency Dispersion ◽  
Uniaxial Stress ◽  
Relaxor Ferroelectrics ◽  
Stress Dependence ◽  
Monte Carlo Investigation ◽  
Stress Dependent

In this work, we used Monte Carlo simulation to investigate the uniaxial stress dependence of the relaxor dielectric properties. The Metropolis algorithm and the spin glass type interaction were used in updating the local polarizations (representing the polar nano-regions). The exchange interaction in the spin glass Hamiltonian was assumed to be stress dependent via the strain. From the results, the frequency dependence of the dielectric permittivity were found, where, at high enough stress, the dielectric permittivity decreases with increasing stresses in qualitatively good agreement with experiments. In addition, from the modified Curie-Weiss law, all ’s stay close to 2. Therefore, this implies the frequency dispersion universality of the relaxor system under loading conditions.

scholarly journals The Primary Origin of Excellent Dielectric Properties of (Co, Nb) Co-Doped TiO2 Ceramics: Electron-Pinned Defect Dipoles vs. Internal Barrier Layer Capacitor Effect

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3230
Author(s):  
Theeranuch Nachaithong ◽  
Narong Chanlek ◽  
Pairot Moontragoon ◽  
Prasit Thongbai
Keyword(s):  
Dielectric Properties ◽  
Loss Tangent ◽  
Barrier Layer ◽  
Dielectric Response ◽  
High Resistivity ◽  
Low Loss ◽  
Rutile Tio2 ◽  
Complex Defect ◽  
Very High ◽  
Co Doped

(Co, Nb) co-doped rutile TiO2 (CoNTO) nanoparticles with low dopant concentrations were prepared using a wet chemistry method. A pure rutile TiO2 phase with a dense microstructure and homogeneous dispersion of the dopants was obtained. By co-doping rutile TiO2 with 0.5 at.% (Co, Nb), a very high dielectric permittivity of ε′ » 36,105 and a low loss tangent of tanδ » 0.04 were achieved. The sample–electrode contact and resistive outer-surface layer (surface barrier layer capacitor) have a significant impact on the dielectric response in the CoNTO ceramics. The density functional theory calculation shows that the 2Co atoms are located near the oxygen vacancy, creating a triangle-shaped 2CoVoTi complex defect. On the other hand, the substitution of TiO2 with Nb atoms can form a diamond-shaped 2Nb2Ti complex defect. These two types of complex defects are far away from each other. Therefore, the electron-pinned defect dipoles cannot be considered the primary origins of the dielectric response in the CoNTO ceramics. Impedance spectroscopy shows that the CoNTO ceramics are electrically heterogeneous, comprised of insulating and semiconducting regions. Thus, the dielectric properties of the CoNTO ceramics are attributed to the interfacial polarization at the internal insulating layers with very high resistivity, giving rise to a low loss tangent.

Uniaxial stress dependence of the Fermi surface of Ru

1984 ◽  
Vol 14 (1) ◽  
pp. 93-96 ◽  
Author(s):  
V E Startsev ◽  
E Fawcett ◽  
M Maszkiewicz ◽  
J M Perz
Keyword(s):  
Fermi Surface ◽  
Uniaxial Stress ◽  
Stress Dependence

scholarly journals Renormalization Group Approach to Pandemics as a Time-Dependent SIR Model

2021 ◽  
Vol 8 ◽  
Author(s):  
Michele Della Morte ◽  
Francesco Sannino
Keyword(s):  
Renormalization Group ◽  
Time Dependence ◽  
Recovery Rate ◽  
Sir Model ◽  
Time Dependent ◽  
Cumulative Number ◽  
Group Approach ◽  
Renormalization Group Approach

We generalise the epidemic Renormalization Group framework while connecting it to a SIR model with time-dependent coefficients. We then confront the model with COVID-19 in Denmark, Germany, Italy and France and show that the approach works rather well in reproducing the data. We also show that a better understanding of the time dependence of the recovery rate would require extending the model to take into account the number of deaths whenever these are over 15% of the cumulative number of infected cases.

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