scholarly journals Debye’s temperature and heat capacity for Sr0.15Ba0.85Bi2Nb2O9 relaxor ferroelectric ceramic

2016 ◽  
Vol 06 (01) ◽  
pp. 1620001
Author(s):  
A. Peláiz-Barranco ◽  
Y. González-Abreu ◽  
P. Saint-Grégoire ◽  
J. D. S. Guerra ◽  
F. Calderón-Piñar
Keyword(s):  
Heat Capacity ◽  
Dielectric Permittivity ◽  
High Frequency ◽  
Frequency Dispersion ◽  
Freezing Temperature ◽  
Ferroelectric Ceramic ◽  
Relaxor Ferroelectric ◽  
Relaxor Behavior ◽  
Temperature Range ◽  
Glass Model

A lead-free relaxor ferroelectric, Sr[Formula: see text]Ba[Formula: see text]Bi2Nb2O9, was synthesized via solid-state reaction and the temperature-dependence of the heat capacity was measured in a wide temperature range. The dielectric permittivity was also measured between 500[Formula: see text]Hz and 5[Formula: see text]MHz in the same temperature range. No anomaly has been detected in the heat capacity curve for the whole temperature range covered in the present experiments, while broad peaks have been observed in the dielectric permittivity with high frequency dispersion. A typical relaxor behavior has been observed from the dielectric analysis. The Debye’s temperature has showed a minimum value near the freezing temperature. The results are discussed considering the spin-glass model and the high frequency dispersion, which has been observed for the studied relaxor system.

scholarly journals Electrocaloric effect and freezing temperature in (Pb0.8Ba0.2)[(Zn1∕3Nb2∕3)0.7Ti0.3]O3 relaxor ferroelectric ceramic

2016 ◽  
Vol 06 (03) ◽  
pp. 1620002 ◽  
Author(s):  
A. Peláiz-Barranco ◽  
F. Calderón-Piñar ◽  
Y. Mendez-González
Keyword(s):  
Critical Temperature ◽  
Indirect Method ◽  
Hysteresis Loops ◽  
Indirect Evidence ◽  
Freezing Temperature ◽  
Ferroelectric Ceramic ◽  
Relaxor Ferroelectric ◽  
Electrocaloric Effect ◽  
Maximum Value ◽  
Polar Nanoregions

The electrocaloric effect (ECE) is studied in (Pb[Formula: see text]Ba[Formula: see text][(Zn[Formula: see text]Nb[Formula: see text]Ti[Formula: see text]]O3 relaxor ferroelectric ceramic by using an “indirect method”. The electric dependence for the polarization (hysteresis loops) has been obtained for several temperatures showing typical relaxor characteristics. The temperature change [Formula: see text], which is associated with the ECE, is calculated by using the temperature dependence for the polarization. A maximum value for [Formula: see text] is observed for temperatures close above the freezing temperature, showing an indirect evidence of that critical temperature. The results are discussed considering the contribution of the polar nanoregions to the polarization.

Effects of lanthanum modification on rhombohedral Pb(Zr1−xTix)O3 ceramics: Part I. Transformation from normal to relaxor ferroelectric behaviors

1996 ◽  
Vol 11 (3) ◽  
pp. 618-625 ◽  
Author(s):  
Xunhu Dai ◽  
Z. Xu ◽  
Jie-Fang Li ◽  
Dwight Viehland
Keyword(s):  
Lattice Distortion ◽  
Cluster State ◽  
Frequency Dispersion ◽  
Relaxor Ferroelectric ◽  
Relaxor Behavior ◽  
Pzt Ceramics ◽  
Polar Order ◽  
Transmission Electron ◽  
Relaxor State ◽  
Domain State

The interruption of long-range polar order in rhombohedral ferroelectricPb(Zr1−xTix)O3 (PZT) ceramics has been systematically studied by incorporating La onto the A-site of the perovskite (ABO3) structure for Zr/Ti ratios of 65/35 and 80/20 and various La contents. Studies have been performed by hot-stage transmission electron microscopy, dielectric spectroscopy, and Sawyer–Tower polarization (P-E) techniques. The evolution of a polar nanodomain state from a normal micron-sized domain state with increasing La content was observed. The emergence of this polar cluster state was characterized by the onset of strong frequency dispersion in the dielectric response, indicative of relaxor behavior. The La content that drives the structure into the relaxor state was found to be related to the lattice distortion of the undoped base composition.

Dielectric abnormity of Sr4Nd2Ti4Nb6O30 tungsten bronze ceramics over a broad temperature range

2007 ◽  
Vol 22 (8) ◽  
pp. 2217-2222 ◽  
Author(s):  
X.L. Zhu ◽  
X.M. Chen ◽  
X.Q. Liu
Keyword(s):  
Tungsten Bronze ◽  
Freezing Temperature ◽  
Broad Temperature Range ◽  
Maximum Temperature ◽  
Relaxor Behavior ◽  
Temperature Range ◽  
Thermally Activated ◽  
Higher Temperature ◽  
Tan Δ ◽  
Lower Temperature

In the present paper, Sr4Nd2Ti4Nb6O30 ceramics with filled tungsten bronze structure were prepared, and the dielectric characteristics over a broad temperature range (123 to 623 K) were investigated. Two dielectric abnormities were observed in the entire frequency range (100 Hz to 1 MHz). One is at higher temperature corresponding to a diffuse ferroelectric transition (P4/mbm → P4bm), and the other at lower temperature shows relaxor characteristics in both ϵ′ and tan δ curves. An activation energy and freezing temperature of 0.1659 eV and 148.05 K, respectively, were obtained by analyzing the frequency dependence of the dielectric maximum temperature using the Vogel–Fulcher relationship. The relaxor behavior is attributed to a polar-glassy system with thermally activated polarization fluctuations above the freezing temperature. In addition, the dielectric constant was almost stable with both temperature and frequency in the temperature range of 300 to 430 K (between the two dielectric abnormities).

Ideal–Gas Thermochemical Properties for Alkanolamine and Related Species Involved in Carbon Capture Applications

2020 ◽  
Author(s):  
Nayyereh hatefi ◽  
William Smith
Keyword(s):  
Heat Capacity ◽  
Electronic Structure ◽  
Co2 Capture ◽  
Carbon Capture ◽  
Ideal Gas ◽  
Thermochemical Properties ◽  
Temperature Range ◽  
Comparison Results ◽  
Electronic Structure Methods ◽  
Protonated Forms

<div>Ideal{gas thermochemical properties (enthalpy, entropy, Gibbs energy, and heat capacity, Cp) of 49 alkanolamines potentially suitable for CO2 capture applications and their carbamate and protonated forms were calculated using two high{order electronic structure methods, G4 and G3B3 (or G3//B3LYP). We also calculate for comparison results from the commonly used B3LYP/aug-cc-pVTZ method. This data is useful for the construction of molecular{based thermodynamic models of CO2 capture processes involving these species. The Cp data for each species over the temperature range 200 K{1500 K is presented as functions of temperature in the form of NASA seven-term polynomial expressions, permitting the set of thermochemical properties to be calculated over this temperature range. The accuracy of the G3B3 and G4 results is estimated to be 1 kcal/mol and the B3LYP/aug-cc-pVTZ results are of nferior quality..</div>

scholarly journals Sintering, Microstructure, and Dielectric Properties of Copper Borates for High Frequency LTCC Applications

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4017
Author(s):  
Dorota Szwagierczak ◽  
Beata Synkiewicz-Musialska ◽  
Jan Kulawik ◽  
Norbert Pałka
Keyword(s):  
Dielectric Properties ◽  
Dielectric Permittivity ◽  
High Frequency ◽  
Ceramic Materials ◽  
Sintering Behavior ◽  
Terahertz Time Domain Spectroscopy ◽  
Very High Frequency ◽  
X Ray ◽  
Low Dielectric ◽  
Very High

New ceramic materials based on two copper borates, CuB2O4 and Cu3B2O6, were prepared via solid state synthesis and sintering, and characterized as promising candidates for low dielectric permittivity substrates for very high frequency circuits. The sintering behavior, composition, microstructure, and dielectric properties of the ceramics were investigated using a heating microscope, X-ray diffractometry, scanning electron microscopy, energy dispersive spectroscopy, and terahertz time domain spectroscopy. The studies revealed a low dielectric permittivity of 5.1–6.7 and low dielectric loss in the frequency range 0.14–0.7 THz. The copper borate-based materials, owing to a low sintering temperature of 900–960 °C, are suitable for LTCC (low temperature cofired ceramics) applications.

Magnetic Permeability and Relaxation Frequency in High Frequency Magnetic Materials.

2001 ◽  
Vol 674 ◽  
Author(s):  
M.I. Rosales ◽  
H. Montiel ◽  
R. Valenzuela
Keyword(s):  
High Frequency ◽  
Domain Walls ◽  
Magnetocrystalline Anisotropy ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Anisotropy Constant ◽  
Relaxation Frequency ◽  
Resonance Relaxation ◽  
Frequency Behavior

ABSTRACTAn investigation of the frequency behavior of polycrystalline ferrites is presented. It is shown that the low frequency dispersion (f < 10 MHz) of permeability is associated with the bulging of pinned domain walls, and has a mixed resonance-relaxation character, closer to the latter. It is also shown that there is a linear relationship between the magnetocrystalline anisotropy constant, K1, and the relaxation frequency. The slope of this correlation depends on the grain size. Such a relationship could allow the determination of this basic parameter from polycrystalline samples.

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